Microbiology
Overview

Microbiology is the study of microorganisms, which are defined as any microscopic
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

, such as fungi and protists, and prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

s. Virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es and prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...

s, though not strictly classed as living organisms, are also studied. Microbiology typically includes the study of the immune system, or Immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

.
Encyclopedia

Microbiology is the study of microorganisms, which are defined as any microscopic
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

, such as fungi and protists, and prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

s. Virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es and prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...

s, though not strictly classed as living organisms, are also studied. Microbiology typically includes the study of the immune system, or Immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

. Generally, immune systems interact with pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

ic microbes; these two disciplines often intersect which is why many colleges offer a paired degree such as "Microbiology and Immunology".

Microbiology is a broad term which includes virology
Virology
Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

, mycology
Mycology
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

, parasitology
Parasitology
Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...

, bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

, immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

 and other branches. A microbiologist
Microbiologist
A microbiologist is a scientist who works in the field of microbiology. Microbiologists study organisms called microbes. Microbes can take the form of bacteria, viruses, fungi, and protists...

 is a specialist in microbiology and these related topics.

Microbiological procedures usually must be aseptic, and use a variety of tools such as light microscopes with a combination of stains and dyes, agar plates in petri dishes, biochemical test and running tests against particular growth conditions. Specific constraints apply to particular fields of microbiology, such as parasitology, which heavily utilizes the light microscopy, whereas microscopy's utility in bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 is limited due to the similarity is many cells physiology. Indeed, most means of differentiating bacteria is based on growth or biochemical reactions. Virology
Virology
Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

 has very little need for light microscopes, relying on almost entirely molecular means. Mycology
Mycology
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

 relies on all technologies the most evenly, from macroscopy to molecular techniques.

Microbiology is actively researched, and the field is advancing continuously. It is estimated that only about one percent of the microorganisms present in a given environmental sample are culturable and the number of bacterial cells and species on Earth is still not possible to be determined, recent estimates indicate that it can be extremely high (5 Exp 30 cells on Earth, unknown number of species). Although microbes were directly observed over three hundred years ago, the precise determination, quantitation and description of its functions is far to be complete, given the overwhelming diversity detected by genetic and culture-independent means.

Ancient

The existence of microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s was hypothesized for many centuries before their actual discovery. The existence of unseen microbiological life was postulated by Jainism
Jainism
Jainism is an Indian religion that prescribes a path of non-violence towards all living beings. Its philosophy and practice emphasize the necessity of self-effort to move the soul towards divine consciousness and liberation. Any soul that has conquered its own inner enemies and achieved the state...

 which is based on Mahavira
Mahavira
Mahāvīra is the name most commonly used to refer to the Indian sage Vardhamāna who established what are today considered to be the central tenets of Jainism. According to Jain tradition, he was the 24th and the last Tirthankara. In Tamil, he is referred to as Arukaṉ or Arukadevan...

’s teachings as early as 6th century BCE. Paul Dundas notes that Mahavira asserted existence of unseen microbiological creatures living in earth, water, air and fire. Jain scriptures also describe nigoda
Nigoda
In Jainism cosmology, the Nigoda is a realm existing in which the lowest forms of life reside in endless numbers, and without any hope of release by self-effort. Jain scriptures describe nigodas which are sub-microscopic creatures living in large clusters and having a very short life and are said...

s which are sub-microscopic creatures living in large clusters and having a very short life and are said to pervade each and every part of the universe, even in tissues of plants and flesh of animals. The Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 Marcus Terentius Varro
Marcus Terentius Varro
Marcus Terentius Varro was an ancient Roman scholar and writer. He is sometimes called Varro Reatinus to distinguish him from his younger contemporary Varro Atacinus.-Biography:...

 made references to microbes when he warned against locating a homestead in the vicinity of swamps "because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there by cause serious diseases."

In 1546 Girolamo Fracastoro
Girolamo Fracastoro
Girolamo Fracastoro was an Italian physician, poet, and scholar in mathematics, geography and astronomy. Fracastoro subscribed to the philosophy of atomism, and rejected appeals to hidden causes in scientific investigation....

 proposed that epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...

 diseases were caused by transferable seedlike entities that could transmit infection by direct or indirect contact, or even without contact over long distances.

However, early claims about the existence of microorganisms were speculative
Speculative
Speculative may refer to:*For economics usage, see Speculation*For usage in literature, see Speculative fiction*For philosophical usage, see Speculative philosophy and Speculative reason...

, and not based on microscopic observation. Actual observation and discovery of microbes had to await the invention of the microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 in the 17th century.

Modern

In 1676, Antonie van Leeuwenhoek observed bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and other microorganisms, using a single-lens microscope of his own design. While Van Leeuwenhoek is often cited as the first to observe microbes, Robert Hooke
Robert Hooke
Robert Hooke FRS was an English natural philosopher, architect and polymath.His adult life comprised three distinct periods: as a scientific inquirer lacking money; achieving great wealth and standing through his reputation for hard work and scrupulous honesty following the great fire of 1666, but...

 made the first recorded microscopic observation, of the fruiting bodies of mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...

s, in 1665. The first observation of microbes using a microscope is generally credited to the Dutch draper and haberdasher, Antonie van Leeuwenhoek, who lived for most of his life in Delft, Holland. It has, however, been suggested that a Jesuit priest called Athanasius Kircher
Athanasius Kircher
Athanasius Kircher was a 17th century German Jesuit scholar who published around 40 works, most notably in the fields of oriental studies, geology, and medicine...

 was the first to observe micro-organisms. He was among the first to design magic lanterns for projection purposes, so he must have been well acquainted with the properties of lenses. One of his book contains a chapter in Latin, which reads in translation – ‘Concerning the wonderful structure of things in nature, investigated by Microscope. Here, he wrote ‘who would believe that vinegar and milk abound with an innumerable multitude of worms.’ He also noted that putrid material is full of innumerable creeping animalcule. These observations antedate Robert Hooke’s Micrographia by nearly 20 years and were published some 29 years before van Leeuwenhoek saw protozoa and 37 years before he described having seen bacteria.
The field of bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 (later a subdiscipline of microbiology) was founded in the 19th century by Ferdinand Cohn
Ferdinand Cohn
Ferdinand Julius Cohn was a German biologist.Cohn was born in Breslau in the Prussian Province of Silesia. At the age of 10 he suffered hearing impairment. He received a degree in botany in 1847 at the age of nineteen at the University of Berlin. He was a teacher and researcher at University of...

, a botanist whose studies on algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

 and photosynthetic bacteria
Phototroph
Phototrophs are the organisms that carry out photosynthesis to acquire energy. They use the energy from sunlight to convert carbon dioxide and water into organic material to be utilized in cellular functions such as biosynthesis and respiration.Most phototrophs are autotrophs, also known as...

 led him to describe several bacteria including Bacillus
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...

and Beggiatoa
Beggiatoa
Beggiatoa is a genus of bacteria in the order Thiotrichales. They are named after the Italian medic and botanist F.S. Beggiato. The organisms live in sulfur-rich environments...

. Cohn was also the first to formulate a scheme for the taxonomic classification of bacteria and discover spores. Louis Pasteur
Louis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...

 and Robert Koch
Robert Koch
Heinrich Hermann Robert Koch was a German physician. He became famous for isolating Bacillus anthracis , the Tuberculosis bacillus and the Vibrio cholerae and for his development of Koch's postulates....

 were contemporaries of Cohn’s and are often considered to be the father of microbiology and medical microbiology
Medical microbiology
Medical microbiology is both a branch of medicine and microbiology which deals with the study of microorganisms including bacteria, viruses, fungi and parasites which are of medical importance and are capable of causing infectious diseases in human beings...

, respectively. Pasteur is most famous for his series of experiments designed to disprove the then widely held theory of spontaneous generation, thereby solidifying microbiology’s identity as a biological science. Pasteur also designed methods for food preservation (pasteurization
Pasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...

) and vaccines against several diseases such as anthrax
Anthrax
Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lethal, and it affects both humans and other animals...

, fowl cholera and rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

. Koch is best known for his contributions to the germ theory of disease
Germ theory of disease
The germ theory of disease, also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases...

, proving that specific diseases were caused by specific pathogenic micro-organisms. He developed a series of criteria that have become known as the Koch's postulates
Koch's postulates
Koch's postulates are four criteria designed to establish a causal relationship between a causative microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890...

. Koch was one of the first scientists to focus on the isolation of bacteria in pure culture resulting in his description of several novel bacteria including Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...

, the causative agent of tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

.

While Pasteur and Koch are often considered the founders of microbiology, their work did not accurately reflect the true diversity of the microbial world because of their exclusive focus on micro-organisms having direct medical relevance. It was not until the late 19th century and the work of Martinus Beijerinck
Martinus Beijerinck
Martinus Willem Beijerinck was a Dutch microbiologist and botanist. Born in Amsterdam, Beijerinck studied at the Technical School of Delft, where he was awarded the degree of Chemical Engineer in 1872. He obtained his Doctor of Science degree from the University of Leiden in 1877...

 and Sergei Winogradsky
Sergei Winogradsky
Sergei Nikolaievich Winogradsky was a Ukrainian-Russian microbiologist, ecologist and soil scientist who pioneered the cycle of life concept. He discovered the first known form of lithotrophy during his research with Beggiatoa in 1887...

, the founders of general microbiology (an older term encompassing aspects of microbial physiology, diversity and ecology), that the true breadth of microbiology was revealed. Beijerinck made two major contributions to microbiology: the discovery of virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es and the development of enrichment culture
Enrichment culture
An enrichment culture is a medium with specific and known qualities that favors the growth of a particular microorganism. The enrichment culture's environment will support the growth of a selected microorganism, while inhibiting the growth of others...

 techniques. While his work on the Tobacco Mosaic Virus
Tobacco mosaic virus
Tobacco mosaic virus is a positive-sense single stranded RNA virus that infects plants, especially tobacco and other members of the family Solanaceae. The infection causes characteristic patterns on the leaves . TMV was the first virus to be discovered...

 established the basic principles of virology, it was his development of enrichment culturing that had the most immediate impact on microbiology by allowing for the cultivation of a wide range of microbes with wildly different physiologies. Winogradsky was the first to develop the concept of chemolithotrophy and to thereby reveal the essential role played by micro-organisms in geochemical processes. He was responsible for the first isolation and description of both nitrifying
Nitrifying bacteria
Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera bacteria that grow by consuming inorganic nitrogen compounds...

 and nitrogen-fixing bacteria.

Branches

The branches of microbiology can be classified into pure and applied sciences. Microbiology can be also classified based on taxonomy, in the cases of bacteriology, mycology, protozoology, and phycology. There is considerable overlap between the specific branches of microbiology with each other and with other disciplines.

Taxonomic arrangement

  • Bacteriology
    Bacteriology
    Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

    : The study of bacteria.
  • Mycology
    Mycology
    Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

    : The study of fungi.
  • Protozoology
    Protozoology
    Protozoology is the study of protozoa, the "animal-like" protists. This term has become dated as our understanding of the evolutionary relationships of the eukaryota has improved....

    : The study of protozoa.
  • Phycology
    Phycology
    Phycology is the scientific study of algae. Phycology is a branch of life science and often is regarded as a subdiscipline of botany....

     (or algology): The study of algae.
  • Parasitology
    Parasitology
    Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...

    : The study of parasites.
  • Immunology
    Immunology
    Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

    : The study of the immune system.
  • Virology
    Virology
    Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

    : The study of the viruses.

Integrative arrangement

  • Microbial cytology: The study of microscopic and submicroscopic details of microorganisms.
  • Microbial physiology: The study of how the microbial cell functions biochemically. Includes the study of microbial growth, microbial metabolism
    Metabolism
    Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

     and microbial cell structure
    Bacterial cell structure
    Bacteria, despite their simplicity, contain a well-developed cell structure which is responsible for many of their unique biological properties. Many structural features are unique to bacteria and are not found among archaea or eukaryotes...

    .
  • Microbial ecology
    Microbial ecology
    Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life — Eukaryota, Archaea, and Bacteria — as well as viruses....

    : The relationship between microorganisms and their environment.
  • Microbial genetics
    Microbial genetics
    Microbial genetics is a subject area within microbiology and genetic engineering. It studies the genetics of very small organisms. This involves the study of the genotype of microbial species and also the expression system in the form of phenotypes.It also involves the study of genetic processes...

    : The study of how gene
    Gene
    A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

    s are organized and regulated in microbes in relation to their cellular functions. Closely related to the field of molecular biology
    Molecular biology
    Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

    .
  • Cellular microbiology
    Cellular microbiology
    Cellular microbiology is a discipline that bridges microbiology and cell biology.The term "cellular microbiology" was coined in 1996 in a Science article...

    : A discipline bridging microbiology and cell biology
    Cell biology
    Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...

    .
  • Evolutionary microbiology: The study of the evolution of microbes. This field can be subdivided into:
    • Microbial taxonomy: The naming and classification of microorganisms.
    • Microbial systematics: The study of the diversity and genetic relationship of microorganisms.
  • Generation microbiology: The study of those microorganisms that have the same characters as their parents.

Other

  • Nano microbiology: The study of those microorganisms at nano level.
  • Exo microbiology (or Astro microbiology): The study of microorganisms in outer space.

Applied microbiology

  • Medical microbiology
    Medical microbiology
    Medical microbiology is both a branch of medicine and microbiology which deals with the study of microorganisms including bacteria, viruses, fungi and parasites which are of medical importance and are capable of causing infectious diseases in human beings...

    : The study of the pathogenic microbes and the role of microbes in human illness. Includes the study of microbial pathogenesis
    Pathogenesis
    The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...

     and epidemiology
    Epidemiology
    Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

     and is related to the study of disease pathology
    Pathology
    Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

     and immunology
    Immunology
    Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

    .
  • Pharmaceutical microbiology
    Pharmaceutical microbiology
    Pharmaceutical microbiology is the part of industrial microbiology that is responsible for ensuring medications do not contain harmful levels of microbes- such as bacteria, yeasts and moulds.- Drug Safety :...

    : The study of microorganisms that are related to the production of antibiotics, enzymes, vitamins,vaccines, and other pharmaceutical products and that cause pharmaceutical contamination and spoil.
  • Industrial microbiology
    Industrial microbiology
    Industrial microbiology or microbial biotechnology encompasses the use of microorganisms in the manufacture of food or industrial products. The use of microorganisms for the production of food, either human or animal, is often considered a branch of food microbiology...

    : The exploitation of microbes for use in industrial processes. Examples include industrial fermentation
    Industrial fermentation
    Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...

     and wastewater treatment
    Wastewater Treatment
    Wastewater treatment may refer to:* Sewage treatment* Industrial wastewater treatment...

    . Closely linked to the biotechnology
    Biotechnology
    Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

     industry. This field also includes brewing
    Brewing
    Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...

    , an important application of microbiology.
  • Microbial biotechnology: The manipulation of microorganisms at the genetic and molecular level to generate useful products.
  • Food microbiology
    Food microbiology
    Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. Of major importance is the study of microorganisms causing food spoilage. "Good" bacteria, however, such as probiotics, are becoming increasingly important in food science...

     and Dairy microbiology: The study of microorganisms causing food spoilage and foodborne illness. Using microorganisms to produce foods, for example by fermentation.
  • Agricultural microbiology
    Agricultural microbiology
    Agricultural microbiology is a branch of microbiology dealing with plant-associated microbes and plant and animal diseases. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations....

    : The study of agriculturally relevant microorganisms. This field can be further classified into the following:
    • Plant microbiology and Plant pathology: The study of the interactions between microorganisms and plants and plant pathogens.
    • Soil microbiology
      Soil microbiology
      Soil microbiology is the study of organisms in soil, their functions, and how they affect soil properties. It is believed that between two to four billion years ago, the first ancient bacteria and microorganisms came about in Earth's primitive seas. These bacteria could fix nitrogen, in time...

      : The study of those microorganisms that are found in soil.
  • Veterinary microbiology: The study of the role in microbes in veterinary medicine
    Veterinary medicine
    Veterinary Medicine is the branch of science that deals with the prevention, diagnosis and treatment of disease, disorder and injury in non-human animals...

     or animal taxonomy
    Taxonomy
    Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

    .
  • Environmental microbiology
    Environmental microbiology
    Environmental microbiology is the study of the composition and physiology of microbial communities in the environment. The environment in this case means the soil, water, air and sediments covering the planet and can also include the animals and plants that inhabit these areas...

    : The study of the function and diversity of microbes in their natural environments. This involves the characterization of key bacterial habitats such as the rhizosphere
    Rhizosphere
    The rhizosphere is the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms. Soil which is not part of the rhizosphere is known as bulk soil. The rhizosphere contains many bacteria that feed on sloughed-off plant cells, termed rhizodeposition, and...

     and phyllosphere
    Phyllosphere
    The phyllosphere is a term used in microbiology to refer to leaf surfaces or total above-ground surfaces of a plant as a habitat for microorganisms. The below-ground microbial habitats The phyllosphere is a term used in microbiology to refer to leaf surfaces or total above-ground surfaces of a...

    , soil
    Soil
    Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

     and groundwater
    Groundwater
    Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

     ecosystem
    Ecosystem
    An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

    s, open oceans or extreme environments (extremophile
    Extremophile
    An extremophile is an organism that thrives in physically or geochemically extreme conditions that are detrimental to most life on Earth. In contrast, organisms that live in more moderate environments may be termed mesophiles or neutrophiles...

    s). This field includes other branches of microbiology such as:
    • Microbial ecology
      Microbial ecology
      Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life — Eukaryota, Archaea, and Bacteria — as well as viruses....

    • Microbially-mediated nutrient cycling
      Nutrient cycle
      A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of living matter. The process is regulated by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within ecosystems...

    • Geomicrobiology
      Geomicrobiology
      Geomicrobiology is the result of the combination of geology and microbiology. The field of geomicrobiology concerns the role of microbe and microbial processes in geological and geochemical processes and vice-versa...

    • Microbial diversity
    • Bioremediation
      Bioremediation
      Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

  • Water microbiology (or Aquatic microbiology): The study of those microorganisms that are found in water.
  • Aeromicrobiology (or Air microbiology): The study of airborne microorganisms.
  • Epidemiology
    Epidemiology
    Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

    : The study of the incidence, spread, and control of disease.

Benefits

Whilst there are undoubtedly some who fear all microbes due to the association of some microbes with various human illnesses, many microbes are also responsible for numerous beneficial processes such as industrial fermentation
Industrial fermentation
Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...

 (e.g. the production of alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

, vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 and dairy products), antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 production and as vehicles for cloning
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...

 in more complex organisms such as plants. Scientists have also exploited their knowledge of microbes to produce biotechnologically important enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s such as Taq polymerase
Taq polymerase
thumb|228px|right|Structure of Taq DNA polymerase bound to a DNA octamerTaq polymerase is a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was originally isolated by Thomas D. Brock in 1965...

, reporter gene
Reporter gene
In molecular biology, a reporter gene is a gene that researchers attach to a regulatory sequence of another gene of interest in cell culture, animals or plants. Certain genes are chosen as reporters because the characteristics they confer on organisms expressing them are easily identified and...

s for use in other genetic systems and novel molecular biology techniques such as the yeast two-hybrid system
Two-hybrid screening
Two-hybrid screening is a molecular biology technique used to discover protein–protein interactions and protein–DNA interactions by testing for physical interactions between two proteins or a single protein and a DNA molecule, respectively.The premise behind the test is the activation of...

.

Bacteria can be used for the industrial production of amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s. Corynebacterium glutamicum is one of the most important bacterial species with an annual production of more than two million tons of amino acids, mainly L-glutamate and L-lysine.

A variety of biopolymer
Biopolymer
Biopolymers are polymers produced by living organisms. Since they are polymers, Biopolymers contain monomeric units that are covalently bonded to form larger structures. There are three main classes of biopolymers based on the differing monomeric units used and the structure of the biopolymer formed...

s, such as polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

s, polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

s, and polyamide
Polyamide
A polyamide is a polymer containing monomers of amides joined by peptide bonds. They can occur both naturally and artificially, examples being proteins, such as wool and silk, and can be made artificially through step-growth polymerization or solid-phase synthesis, examples being nylons, aramids,...

s, are produced by microorganisms. Microorganisms are used for the biotechnological production of biopolymers with tailored properties suitable for high-value medical application such as tissue engineering
Tissue engineering
Tissue engineering is the use of a combination of cells, engineering and materials methods, and suitable biochemical and physio-chemical factors to improve or replace biological functions...

 and drug delivery. Microorganisms are used for the biosynthesis of xanthan, alginate, cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

, cyanophycin
Cyanophycin
Cyanophycin, or multi-L-arginyl-poly , is a non-protein, non-ribosomally produced amino acid polymer composed of an aspartic acid backbone and arginine side groups....

, poly(gamma-glutamic acid), levan
Levan
Levan can refer to:* Levan, a homopolysaccharide which is composed of D-fructofuranosyl* A group of fructans produced by bacteria or created by breaking down other kinds of plant fructans, called levan beta 2→6* The town of Levan, Utah...

, hyaluronic acid, organic acids, oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...

s and polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

, and polyhydroxyalkanoates.

Microorganisms are beneficial for microbial biodegradation
Microbial biodegradation
Interest in the microbial biodegradation of pollutants has intensified in recent years as humanity strives to find sustainable ways to clean up contaminated environments...

 or bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

 of domestic, agricultural and industrial wastes and subsurface pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 in soils, sediments and marine environments. The ability of each microorganism to degrade toxic waste
Toxic waste
Toxic waste is waste material that can cause death or injury to living creatures. It spreads quite easily and can contaminate lakes and rivers. The term is often used interchangeably with “hazardous waste”, or discarded material that can pose a long-term risk to health or environment.Toxic waste...

 depends on the nature of each contaminant. Since sites typically have multiple pollutant types, the most effective approach to microbial biodegradation
Microbial biodegradation
Interest in the microbial biodegradation of pollutants has intensified in recent years as humanity strives to find sustainable ways to clean up contaminated environments...

 is to use a mixture of bacterial species and strains, each specific to the biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...

 of one or more types of contaminants.

There are also various claims concerning the contributions to human and animal health by consuming probiotics (bacteria potentially beneficial to the digestive system) and/or prebiotics (substances consumed to promote the growth of probiotic microorganisms).

Recent research has suggested that microorganisms could be useful in the treatment of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. Various strains of non-pathogenic clostridia
Clostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...

 can infiltrate and replicate within solid tumors. Clostridial vectors can be safely administered and their potential to deliver therapeutic proteins has been demonstrated in a variety of preclinical models.

Microbiology (from Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 , mīkros, "small"; , bios, "life
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...

"; and , -logia
-logy
-logy is a suffix in the English language, used with words originally adapted from Ancient Greek language ending in -λογία...

) is the study of microorganisms, which are defined as any microscopic
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

, such as fungi and protists, and prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

s. Virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es and prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...

s, though not strictly classed as living organisms, are also studied. Microbiology typically includes the study of the immune system, or Immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

. Generally, immune systems interact with pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

ic microbes; these two disciplines often intersect which is why many colleges offer a paired degree such as "Microbiology and Immunology".

Microbiology is a broad term which includes virology
Virology
Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

, mycology
Mycology
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

, parasitology
Parasitology
Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...

, bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

, immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

 and other branches. A microbiologist
Microbiologist
A microbiologist is a scientist who works in the field of microbiology. Microbiologists study organisms called microbes. Microbes can take the form of bacteria, viruses, fungi, and protists...

 is a specialist in microbiology and these related topics.

Microbiological procedures usually must be aseptic, and use a variety of tools such as light microscopes with a combination of stains and dyes, agar plates in petri dishes, biochemical test and running tests against particular growth conditions. Specific constraints apply to particular fields of microbiology, such as parasitology, which heavily utilizes the light microscopy, whereas microscopy's utility in bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 is limited due to the similarity is many cells physiology. Indeed, most means of differentiating bacteria is based on growth or biochemical reactions. Virology
Virology
Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

 has very little need for light microscopes, relying on almost entirely molecular means. Mycology
Mycology
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

 relies on all technologies the most evenly, from macroscopy to molecular techniques.

Microbiology is actively researched, and the field is advancing continuously. It is estimated that only about one percent of the microorganisms present in a given environmental sample are culturable and the number of bacterial cells and species on Earth is still not possible to be determined, recent estimates indicate that it can be extremely high (5 Exp 30 cells on Earth, unknown number of species). Although microbes were directly observed over three hundred years ago, the precise determination, quantitation and description of its functions is far to be complete, given the overwhelming diversity detected by genetic and culture-independent means.

Ancient

The existence of microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s was hypothesized for many centuries before their actual discovery. The existence of unseen microbiological life was postulated by Jainism
Jainism
Jainism is an Indian religion that prescribes a path of non-violence towards all living beings. Its philosophy and practice emphasize the necessity of self-effort to move the soul towards divine consciousness and liberation. Any soul that has conquered its own inner enemies and achieved the state...

 which is based on Mahavira
Mahavira
Mahāvīra is the name most commonly used to refer to the Indian sage Vardhamāna who established what are today considered to be the central tenets of Jainism. According to Jain tradition, he was the 24th and the last Tirthankara. In Tamil, he is referred to as Arukaṉ or Arukadevan...

’s teachings as early as 6th century BCE. Paul Dundas notes that Mahavira asserted existence of unseen microbiological creatures living in earth, water, air and fire. Jain scriptures also describe nigoda
Nigoda
In Jainism cosmology, the Nigoda is a realm existing in which the lowest forms of life reside in endless numbers, and without any hope of release by self-effort. Jain scriptures describe nigodas which are sub-microscopic creatures living in large clusters and having a very short life and are said...

s which are sub-microscopic creatures living in large clusters and having a very short life and are said to pervade each and every part of the universe, even in tissues of plants and flesh of animals. The Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 Marcus Terentius Varro
Marcus Terentius Varro
Marcus Terentius Varro was an ancient Roman scholar and writer. He is sometimes called Varro Reatinus to distinguish him from his younger contemporary Varro Atacinus.-Biography:...

 made references to microbes when he warned against locating a homestead in the vicinity of swamps "because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there by cause serious diseases."

In 1546 Girolamo Fracastoro
Girolamo Fracastoro
Girolamo Fracastoro was an Italian physician, poet, and scholar in mathematics, geography and astronomy. Fracastoro subscribed to the philosophy of atomism, and rejected appeals to hidden causes in scientific investigation....

 proposed that epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...

 diseases were caused by transferable seedlike entities that could transmit infection by direct or indirect contact, or even without contact over long distances.

However, early claims about the existence of microorganisms were speculative
Speculative
Speculative may refer to:*For economics usage, see Speculation*For usage in literature, see Speculative fiction*For philosophical usage, see Speculative philosophy and Speculative reason...

, and not based on microscopic observation. Actual observation and discovery of microbes had to await the invention of the microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 in the 17th century.

Modern

In 1676, Antonie van Leeuwenhoek observed bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and other microorganisms, using a single-lens microscope of his own design. While Van Leeuwenhoek is often cited as the first to observe microbes, Robert Hooke
Robert Hooke
Robert Hooke FRS was an English natural philosopher, architect and polymath.His adult life comprised three distinct periods: as a scientific inquirer lacking money; achieving great wealth and standing through his reputation for hard work and scrupulous honesty following the great fire of 1666, but...

 made the first recorded microscopic observation, of the fruiting bodies of mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...

s, in 1665. The first observation of microbes using a microscope is generally credited to the Dutch draper and haberdasher, Antonie van Leeuwenhoek, who lived for most of his life in Delft, Holland. It has, however, been suggested that a Jesuit priest called Athanasius Kircher
Athanasius Kircher
Athanasius Kircher was a 17th century German Jesuit scholar who published around 40 works, most notably in the fields of oriental studies, geology, and medicine...

 was the first to observe micro-organisms. He was among the first to design magic lanterns for projection purposes, so he must have been well acquainted with the properties of lenses. One of his book contains a chapter in Latin, which reads in translation – ‘Concerning the wonderful structure of things in nature, investigated by Microscope. Here, he wrote ‘who would believe that vinegar and milk abound with an innumerable multitude of worms.’ He also noted that putrid material is full of innumerable creeping animalcule. These observations antedate Robert Hooke’s Micrographia by nearly 20 years and were published some 29 years before van Leeuwenhoek saw protozoa and 37 years before he described having seen bacteria.
The field of bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 (later a subdiscipline of microbiology) was founded in the 19th century by Ferdinand Cohn
Ferdinand Cohn
Ferdinand Julius Cohn was a German biologist.Cohn was born in Breslau in the Prussian Province of Silesia. At the age of 10 he suffered hearing impairment. He received a degree in botany in 1847 at the age of nineteen at the University of Berlin. He was a teacher and researcher at University of...

, a botanist whose studies on algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

 and photosynthetic bacteria
Phototroph
Phototrophs are the organisms that carry out photosynthesis to acquire energy. They use the energy from sunlight to convert carbon dioxide and water into organic material to be utilized in cellular functions such as biosynthesis and respiration.Most phototrophs are autotrophs, also known as...

 led him to describe several bacteria including Bacillus
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...

and Beggiatoa
Beggiatoa
Beggiatoa is a genus of bacteria in the order Thiotrichales. They are named after the Italian medic and botanist F.S. Beggiato. The organisms live in sulfur-rich environments...

. Cohn was also the first to formulate a scheme for the taxonomic classification of bacteria and discover spores. Louis Pasteur
Louis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...

 and Robert Koch
Robert Koch
Heinrich Hermann Robert Koch was a German physician. He became famous for isolating Bacillus anthracis , the Tuberculosis bacillus and the Vibrio cholerae and for his development of Koch's postulates....

 were contemporaries of Cohn’s and are often considered to be the father of microbiology and medical microbiology
Medical microbiology
Medical microbiology is both a branch of medicine and microbiology which deals with the study of microorganisms including bacteria, viruses, fungi and parasites which are of medical importance and are capable of causing infectious diseases in human beings...

, respectively. Pasteur is most famous for his series of experiments designed to disprove the then widely held theory of spontaneous generation, thereby solidifying microbiology’s identity as a biological science. Pasteur also designed methods for food preservation (pasteurization
Pasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...

) and vaccines against several diseases such as anthrax
Anthrax
Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lethal, and it affects both humans and other animals...

, fowl cholera and rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

. Koch is best known for his contributions to the germ theory of disease
Germ theory of disease
The germ theory of disease, also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases...

, proving that specific diseases were caused by specific pathogenic micro-organisms. He developed a series of criteria that have become known as the Koch's postulates
Koch's postulates
Koch's postulates are four criteria designed to establish a causal relationship between a causative microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890...

. Koch was one of the first scientists to focus on the isolation of bacteria in pure culture resulting in his description of several novel bacteria including Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...

, the causative agent of tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

.

While Pasteur and Koch are often considered the founders of microbiology, their work did not accurately reflect the true diversity of the microbial world because of their exclusive focus on micro-organisms having direct medical relevance. It was not until the late 19th century and the work of Martinus Beijerinck
Martinus Beijerinck
Martinus Willem Beijerinck was a Dutch microbiologist and botanist. Born in Amsterdam, Beijerinck studied at the Technical School of Delft, where he was awarded the degree of Chemical Engineer in 1872. He obtained his Doctor of Science degree from the University of Leiden in 1877...

 and Sergei Winogradsky
Sergei Winogradsky
Sergei Nikolaievich Winogradsky was a Ukrainian-Russian microbiologist, ecologist and soil scientist who pioneered the cycle of life concept. He discovered the first known form of lithotrophy during his research with Beggiatoa in 1887...

, the founders of general microbiology (an older term encompassing aspects of microbial physiology, diversity and ecology), that the true breadth of microbiology was revealed. Beijerinck made two major contributions to microbiology: the discovery of virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es and the development of enrichment culture
Enrichment culture
An enrichment culture is a medium with specific and known qualities that favors the growth of a particular microorganism. The enrichment culture's environment will support the growth of a selected microorganism, while inhibiting the growth of others...

techniques. While his work on the Tobacco Mosaic Virus
Tobacco mosaic virus
Tobacco mosaic virus is a positive-sense single stranded RNA virus that infects plants, especially tobacco and other members of the family Solanaceae. The infection causes characteristic patterns on the leaves . TMV was the first virus to be discovered...

 established the basic principles of virology, it was his development of enrichment culturing that had the most immediate impact on microbiology by allowing for the cultivation of a wide range of microbes with wildly different physiologies. Winogradsky was the first to develop the concept of chemolithotrophy and to thereby reveal the essential role played by micro-organisms in geochemical processes. He was responsible for the first isolation and description of both nitrifying
Nitrifying bacteria
Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera bacteria that grow by consuming inorganic nitrogen compounds...

 and nitrogen-fixing bacteria.

Branches

The branches of microbiology can be classified into pure and applied sciences. Microbiology can be also classified based on taxonomy, in the cases of bacteriology, mycology, protozoology, and phycology. There is considerable overlap between the specific branches of microbiology with each other and with other disciplines.

Taxonomic arrangement

  • Bacteriology
    Bacteriology
    Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

    : The study of bacteria.
  • Mycology
    Mycology
    Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

    : The study of fungi.
  • Protozoology
    Protozoology
    Protozoology is the study of protozoa, the "animal-like" protists. This term has become dated as our understanding of the evolutionary relationships of the eukaryota has improved....

    : The study of protozoa.
  • Phycology
    Phycology
    Phycology is the scientific study of algae. Phycology is a branch of life science and often is regarded as a subdiscipline of botany....

     (or algology): The study of algae.
  • Parasitology
    Parasitology
    Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...

    : The study of parasites.
  • Immunology
    Immunology
    Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

    : The study of the immune system.
  • Virology
    Virology
    Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

    : The study of the viruses.

Integrative arrangement

  • Microbial cytology: The study of microscopic and submicroscopic details of microorganisms.
  • Microbial physiology: The study of how the microbial cell functions biochemically. Includes the study of microbial growth, microbial metabolism
    Metabolism
    Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

     and microbial cell structure
    Bacterial cell structure
    Bacteria, despite their simplicity, contain a well-developed cell structure which is responsible for many of their unique biological properties. Many structural features are unique to bacteria and are not found among archaea or eukaryotes...

    .
  • Microbial ecology
    Microbial ecology
    Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life — Eukaryota, Archaea, and Bacteria — as well as viruses....

    : The relationship between microorganisms and their environment.
  • Microbial genetics
    Microbial genetics
    Microbial genetics is a subject area within microbiology and genetic engineering. It studies the genetics of very small organisms. This involves the study of the genotype of microbial species and also the expression system in the form of phenotypes.It also involves the study of genetic processes...

    : The study of how gene
    Gene
    A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

    s are organized and regulated in microbes in relation to their cellular functions. Closely related to the field of molecular biology
    Molecular biology
    Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

    .
  • Cellular microbiology
    Cellular microbiology
    Cellular microbiology is a discipline that bridges microbiology and cell biology.The term "cellular microbiology" was coined in 1996 in a Science article...

    : A discipline bridging microbiology and cell biology
    Cell biology
    Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...

    .
  • Evolutionary microbiology: The study of the evolution of microbes. This field can be subdivided into:
    • Microbial taxonomy: The naming and classification of microorganisms.
    • Microbial systematics: The study of the diversity and genetic relationship of microorganisms.
  • Generation microbiology: The study of those microorganisms that have the same characters as their parents.

Other

  • Nano microbiology: The study of those microorganisms at nano level.
  • Exo microbiology (or Astro microbiology): The study of microorganisms in outer space.

Applied microbiology

  • Medical microbiology
    Medical microbiology
    Medical microbiology is both a branch of medicine and microbiology which deals with the study of microorganisms including bacteria, viruses, fungi and parasites which are of medical importance and are capable of causing infectious diseases in human beings...

    : The study of the pathogenic microbes and the role of microbes in human illness. Includes the study of microbial pathogenesis
    Pathogenesis
    The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...

     and epidemiology
    Epidemiology
    Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

     and is related to the study of disease pathology
    Pathology
    Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

     and immunology
    Immunology
    Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

    .
  • Pharmaceutical microbiology
    Pharmaceutical microbiology
    Pharmaceutical microbiology is the part of industrial microbiology that is responsible for ensuring medications do not contain harmful levels of microbes- such as bacteria, yeasts and moulds.- Drug Safety :...

    : The study of microorganisms that are related to the production of antibiotics, enzymes, vitamins,vaccines, and other pharmaceutical products and that cause pharmaceutical contamination and spoil.
  • Industrial microbiology
    Industrial microbiology
    Industrial microbiology or microbial biotechnology encompasses the use of microorganisms in the manufacture of food or industrial products. The use of microorganisms for the production of food, either human or animal, is often considered a branch of food microbiology...

    : The exploitation of microbes for use in industrial processes. Examples include industrial fermentation
    Industrial fermentation
    Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...

     and wastewater treatment
    Wastewater Treatment
    Wastewater treatment may refer to:* Sewage treatment* Industrial wastewater treatment...

    . Closely linked to the biotechnology
    Biotechnology
    Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

     industry. This field also includes brewing
    Brewing
    Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...

    , an important application of microbiology.
  • Microbial biotechnology: The manipulation of microorganisms at the genetic and molecular level to generate useful products.
  • Food microbiology
    Food microbiology
    Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. Of major importance is the study of microorganisms causing food spoilage. "Good" bacteria, however, such as probiotics, are becoming increasingly important in food science...

     and Dairy microbiology: The study of microorganisms causing food spoilage and foodborne illness. Using microorganisms to produce foods, for example by fermentation.
  • Agricultural microbiology
    Agricultural microbiology
    Agricultural microbiology is a branch of microbiology dealing with plant-associated microbes and plant and animal diseases. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations....

    : The study of agriculturally relevant microorganisms. This field can be further classified into the following:
    • Plant microbiology and Plant pathology: The study of the interactions between microorganisms and plants and plant pathogens.
    • Soil microbiology
      Soil microbiology
      Soil microbiology is the study of organisms in soil, their functions, and how they affect soil properties. It is believed that between two to four billion years ago, the first ancient bacteria and microorganisms came about in Earth's primitive seas. These bacteria could fix nitrogen, in time...

      : The study of those microorganisms that are found in soil.
  • Veterinary microbiology: The study of the role in microbes in veterinary medicine
    Veterinary medicine
    Veterinary Medicine is the branch of science that deals with the prevention, diagnosis and treatment of disease, disorder and injury in non-human animals...

     or animal taxonomy
    Taxonomy
    Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

    .
  • Environmental microbiology
    Environmental microbiology
    Environmental microbiology is the study of the composition and physiology of microbial communities in the environment. The environment in this case means the soil, water, air and sediments covering the planet and can also include the animals and plants that inhabit these areas...

    : The study of the function and diversity of microbes in their natural environments. This involves the characterization of key bacterial habitats such as the rhizosphere
    Rhizosphere
    The rhizosphere is the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms. Soil which is not part of the rhizosphere is known as bulk soil. The rhizosphere contains many bacteria that feed on sloughed-off plant cells, termed rhizodeposition, and...

     and phyllosphere
    Phyllosphere
    The phyllosphere is a term used in microbiology to refer to leaf surfaces or total above-ground surfaces of a plant as a habitat for microorganisms. The below-ground microbial habitats The phyllosphere is a term used in microbiology to refer to leaf surfaces or total above-ground surfaces of a...

    , soil
    Soil
    Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

     and groundwater
    Groundwater
    Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

     ecosystem
    Ecosystem
    An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

    s, open oceans or extreme environments (extremophile
    Extremophile
    An extremophile is an organism that thrives in physically or geochemically extreme conditions that are detrimental to most life on Earth. In contrast, organisms that live in more moderate environments may be termed mesophiles or neutrophiles...

    s). This field includes other branches of microbiology such as:
    • Microbial ecology
      Microbial ecology
      Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life — Eukaryota, Archaea, and Bacteria — as well as viruses....

    • Microbially-mediated nutrient cycling
      Nutrient cycle
      A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of living matter. The process is regulated by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within ecosystems...

    • Geomicrobiology
      Geomicrobiology
      Geomicrobiology is the result of the combination of geology and microbiology. The field of geomicrobiology concerns the role of microbe and microbial processes in geological and geochemical processes and vice-versa...

    • Microbial diversity
    • Bioremediation
      Bioremediation
      Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

  • Water microbiology (or Aquatic microbiology): The study of those microorganisms that are found in water.
  • Aeromicrobiology (or Air microbiology): The study of airborne microorganisms.
  • Epidemiology
    Epidemiology
    Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

    : The study of the incidence, spread, and control of disease.

Benefits

Whilst there are undoubtedly some who fear all microbes due to the association of some microbes with various human illnesses, many microbes are also responsible for numerous beneficial processes such as industrial fermentation
Industrial fermentation
Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...

 (e.g. the production of alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

, vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 and dairy products), antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 production and as vehicles for cloning
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...

 in more complex organisms such as plants. Scientists have also exploited their knowledge of microbes to produce biotechnologically important enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s such as Taq polymerase
Taq polymerase
thumb|228px|right|Structure of Taq DNA polymerase bound to a DNA octamerTaq polymerase is a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was originally isolated by Thomas D. Brock in 1965...

, reporter gene
Reporter gene
In molecular biology, a reporter gene is a gene that researchers attach to a regulatory sequence of another gene of interest in cell culture, animals or plants. Certain genes are chosen as reporters because the characteristics they confer on organisms expressing them are easily identified and...

s for use in other genetic systems and novel molecular biology techniques such as the yeast two-hybrid system
Two-hybrid screening
Two-hybrid screening is a molecular biology technique used to discover protein–protein interactions and protein–DNA interactions by testing for physical interactions between two proteins or a single protein and a DNA molecule, respectively.The premise behind the test is the activation of...

.

Bacteria can be used for the industrial production of amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s. Corynebacterium glutamicum is one of the most important bacterial species with an annual production of more than two million tons of amino acids, mainly L-glutamate and L-lysine.

A variety of biopolymer
Biopolymer
Biopolymers are polymers produced by living organisms. Since they are polymers, Biopolymers contain monomeric units that are covalently bonded to form larger structures. There are three main classes of biopolymers based on the differing monomeric units used and the structure of the biopolymer formed...

s, such as polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

s, polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

s, and polyamide
Polyamide
A polyamide is a polymer containing monomers of amides joined by peptide bonds. They can occur both naturally and artificially, examples being proteins, such as wool and silk, and can be made artificially through step-growth polymerization or solid-phase synthesis, examples being nylons, aramids,...

s, are produced by microorganisms. Microorganisms are used for the biotechnological production of biopolymers with tailored properties suitable for high-value medical application such as tissue engineering
Tissue engineering
Tissue engineering is the use of a combination of cells, engineering and materials methods, and suitable biochemical and physio-chemical factors to improve or replace biological functions...

 and drug delivery. Microorganisms are used for the biosynthesis of xanthan, alginate, cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

, cyanophycin
Cyanophycin
Cyanophycin, or multi-L-arginyl-poly , is a non-protein, non-ribosomally produced amino acid polymer composed of an aspartic acid backbone and arginine side groups....

, poly(gamma-glutamic acid), levan
Levan
Levan can refer to:* Levan, a homopolysaccharide which is composed of D-fructofuranosyl* A group of fructans produced by bacteria or created by breaking down other kinds of plant fructans, called levan beta 2→6* The town of Levan, Utah...

, hyaluronic acid, organic acids, oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...

s and polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

, and polyhydroxyalkanoates.

Microorganisms are beneficial for microbial biodegradation
Microbial biodegradation
Interest in the microbial biodegradation of pollutants has intensified in recent years as humanity strives to find sustainable ways to clean up contaminated environments...

 or bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

 of domestic, agricultural and industrial wastes and subsurface pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 in soils, sediments and marine environments. The ability of each microorganism to degrade toxic waste
Toxic waste
Toxic waste is waste material that can cause death or injury to living creatures. It spreads quite easily and can contaminate lakes and rivers. The term is often used interchangeably with “hazardous waste”, or discarded material that can pose a long-term risk to health or environment.Toxic waste...

 depends on the nature of each contaminant. Since sites typically have multiple pollutant types, the most effective approach to microbial biodegradation
Microbial biodegradation
Interest in the microbial biodegradation of pollutants has intensified in recent years as humanity strives to find sustainable ways to clean up contaminated environments...

 is to use a mixture of bacterial species and strains, each specific to the biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...

 of one or more types of contaminants.

There are also various claims concerning the contributions to human and animal health by consuming probiotics (bacteria potentially beneficial to the digestive system) and/or prebiotics (substances consumed to promote the growth of probiotic microorganisms).

Recent research has suggested that microorganisms could be useful in the treatment of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. Various strains of non-pathogenic clostridia
Clostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...

 can infiltrate and replicate within solid tumors. Clostridial vectors can be safely administered and their potential to deliver therapeutic proteins has been demonstrated in a variety of preclinical models.

Microbiology (from Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 , mīkros, "small"; , bios, "life
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...

"; and , -logia
-logy
-logy is a suffix in the English language, used with words originally adapted from Ancient Greek language ending in -λογία...

) is the study of microorganisms, which are defined as any microscopic
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

, such as fungi and protists, and prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

s. Virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es and prion
Prion
A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...

s, though not strictly classed as living organisms, are also studied. Microbiology typically includes the study of the immune system, or Immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

. Generally, immune systems interact with pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

ic microbes; these two disciplines often intersect which is why many colleges offer a paired degree such as "Microbiology and Immunology".

Microbiology is a broad term which includes virology
Virology
Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

, mycology
Mycology
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

, parasitology
Parasitology
Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...

, bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

, immunology
Immunology
Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

 and other branches. A microbiologist
Microbiologist
A microbiologist is a scientist who works in the field of microbiology. Microbiologists study organisms called microbes. Microbes can take the form of bacteria, viruses, fungi, and protists...

 is a specialist in microbiology and these related topics.

Microbiological procedures usually must be aseptic, and use a variety of tools such as light microscopes with a combination of stains and dyes, agar plates in petri dishes, biochemical test and running tests against particular growth conditions. Specific constraints apply to particular fields of microbiology, such as parasitology, which heavily utilizes the light microscopy, whereas microscopy's utility in bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 is limited due to the similarity is many cells physiology. Indeed, most means of differentiating bacteria is based on growth or biochemical reactions. Virology
Virology
Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

 has very little need for light microscopes, relying on almost entirely molecular means. Mycology
Mycology
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

 relies on all technologies the most evenly, from macroscopy to molecular techniques.

Microbiology is actively researched, and the field is advancing continuously. It is estimated that only about one percent of the microorganisms present in a given environmental sample are culturable and the number of bacterial cells and species on Earth is still not possible to be determined, recent estimates indicate that it can be extremely high (5 Exp 30 cells on Earth, unknown number of species). Although microbes were directly observed over three hundred years ago, the precise determination, quantitation and description of its functions is far to be complete, given the overwhelming diversity detected by genetic and culture-independent means.

Ancient

The existence of microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s was hypothesized for many centuries before their actual discovery. The existence of unseen microbiological life was postulated by Jainism
Jainism
Jainism is an Indian religion that prescribes a path of non-violence towards all living beings. Its philosophy and practice emphasize the necessity of self-effort to move the soul towards divine consciousness and liberation. Any soul that has conquered its own inner enemies and achieved the state...

 which is based on Mahavira
Mahavira
Mahāvīra is the name most commonly used to refer to the Indian sage Vardhamāna who established what are today considered to be the central tenets of Jainism. According to Jain tradition, he was the 24th and the last Tirthankara. In Tamil, he is referred to as Arukaṉ or Arukadevan...

’s teachings as early as 6th century BCE. Paul Dundas notes that Mahavira asserted existence of unseen microbiological creatures living in earth, water, air and fire. Jain scriptures also describe nigoda
Nigoda
In Jainism cosmology, the Nigoda is a realm existing in which the lowest forms of life reside in endless numbers, and without any hope of release by self-effort. Jain scriptures describe nigodas which are sub-microscopic creatures living in large clusters and having a very short life and are said...

s which are sub-microscopic creatures living in large clusters and having a very short life and are said to pervade each and every part of the universe, even in tissues of plants and flesh of animals. The Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 Marcus Terentius Varro
Marcus Terentius Varro
Marcus Terentius Varro was an ancient Roman scholar and writer. He is sometimes called Varro Reatinus to distinguish him from his younger contemporary Varro Atacinus.-Biography:...

 made references to microbes when he warned against locating a homestead in the vicinity of swamps "because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there by cause serious diseases."

In 1546 Girolamo Fracastoro
Girolamo Fracastoro
Girolamo Fracastoro was an Italian physician, poet, and scholar in mathematics, geography and astronomy. Fracastoro subscribed to the philosophy of atomism, and rejected appeals to hidden causes in scientific investigation....

 proposed that epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...

 diseases were caused by transferable seedlike entities that could transmit infection by direct or indirect contact, or even without contact over long distances.

However, early claims about the existence of microorganisms were speculative
Speculative
Speculative may refer to:*For economics usage, see Speculation*For usage in literature, see Speculative fiction*For philosophical usage, see Speculative philosophy and Speculative reason...

, and not based on microscopic observation. Actual observation and discovery of microbes had to await the invention of the microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 in the 17th century.

Modern

In 1676, Antonie van Leeuwenhoek observed bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and other microorganisms, using a single-lens microscope of his own design. While Van Leeuwenhoek is often cited as the first to observe microbes, Robert Hooke
Robert Hooke
Robert Hooke FRS was an English natural philosopher, architect and polymath.His adult life comprised three distinct periods: as a scientific inquirer lacking money; achieving great wealth and standing through his reputation for hard work and scrupulous honesty following the great fire of 1666, but...

 made the first recorded microscopic observation, of the fruiting bodies of mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...

s, in 1665. The first observation of microbes using a microscope is generally credited to the Dutch draper and haberdasher, Antonie van Leeuwenhoek, who lived for most of his life in Delft, Holland. It has, however, been suggested that a Jesuit priest called Athanasius Kircher
Athanasius Kircher
Athanasius Kircher was a 17th century German Jesuit scholar who published around 40 works, most notably in the fields of oriental studies, geology, and medicine...

 was the first to observe micro-organisms. He was among the first to design magic lanterns for projection purposes, so he must have been well acquainted with the properties of lenses. One of his book contains a chapter in Latin, which reads in translation – ‘Concerning the wonderful structure of things in nature, investigated by Microscope. Here, he wrote ‘who would believe that vinegar and milk abound with an innumerable multitude of worms.’ He also noted that putrid material is full of innumerable creeping animalcule. These observations antedate Robert Hooke’s Micrographia by nearly 20 years and were published some 29 years before van Leeuwenhoek saw protozoa and 37 years before he described having seen bacteria.
The field of bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 (later a subdiscipline of microbiology) was founded in the 19th century by Ferdinand Cohn
Ferdinand Cohn
Ferdinand Julius Cohn was a German biologist.Cohn was born in Breslau in the Prussian Province of Silesia. At the age of 10 he suffered hearing impairment. He received a degree in botany in 1847 at the age of nineteen at the University of Berlin. He was a teacher and researcher at University of...

, a botanist whose studies on algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

 and photosynthetic bacteria
Phototroph
Phototrophs are the organisms that carry out photosynthesis to acquire energy. They use the energy from sunlight to convert carbon dioxide and water into organic material to be utilized in cellular functions such as biosynthesis and respiration.Most phototrophs are autotrophs, also known as...

 led him to describe several bacteria including Bacillus
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...

and Beggiatoa
Beggiatoa
Beggiatoa is a genus of bacteria in the order Thiotrichales. They are named after the Italian medic and botanist F.S. Beggiato. The organisms live in sulfur-rich environments...

. Cohn was also the first to formulate a scheme for the taxonomic classification of bacteria and discover spores. Louis Pasteur
Louis Pasteur
Louis Pasteur was a French chemist and microbiologist born in Dole. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax. His experiments...

 and Robert Koch
Robert Koch
Heinrich Hermann Robert Koch was a German physician. He became famous for isolating Bacillus anthracis , the Tuberculosis bacillus and the Vibrio cholerae and for his development of Koch's postulates....

 were contemporaries of Cohn’s and are often considered to be the father of microbiology and medical microbiology
Medical microbiology
Medical microbiology is both a branch of medicine and microbiology which deals with the study of microorganisms including bacteria, viruses, fungi and parasites which are of medical importance and are capable of causing infectious diseases in human beings...

, respectively. Pasteur is most famous for his series of experiments designed to disprove the then widely held theory of spontaneous generation, thereby solidifying microbiology’s identity as a biological science. Pasteur also designed methods for food preservation (pasteurization
Pasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...

) and vaccines against several diseases such as anthrax
Anthrax
Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lethal, and it affects both humans and other animals...

, fowl cholera and rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

. Koch is best known for his contributions to the germ theory of disease
Germ theory of disease
The germ theory of disease, also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases...

, proving that specific diseases were caused by specific pathogenic micro-organisms. He developed a series of criteria that have become known as the Koch's postulates
Koch's postulates
Koch's postulates are four criteria designed to establish a causal relationship between a causative microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890...

. Koch was one of the first scientists to focus on the isolation of bacteria in pure culture resulting in his description of several novel bacteria including Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...

, the causative agent of tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

.

While Pasteur and Koch are often considered the founders of microbiology, their work did not accurately reflect the true diversity of the microbial world because of their exclusive focus on micro-organisms having direct medical relevance. It was not until the late 19th century and the work of Martinus Beijerinck
Martinus Beijerinck
Martinus Willem Beijerinck was a Dutch microbiologist and botanist. Born in Amsterdam, Beijerinck studied at the Technical School of Delft, where he was awarded the degree of Chemical Engineer in 1872. He obtained his Doctor of Science degree from the University of Leiden in 1877...

 and Sergei Winogradsky
Sergei Winogradsky
Sergei Nikolaievich Winogradsky was a Ukrainian-Russian microbiologist, ecologist and soil scientist who pioneered the cycle of life concept. He discovered the first known form of lithotrophy during his research with Beggiatoa in 1887...

, the founders of general microbiology (an older term encompassing aspects of microbial physiology, diversity and ecology), that the true breadth of microbiology was revealed. Beijerinck made two major contributions to microbiology: the discovery of virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es and the development of enrichment culture
Enrichment culture
An enrichment culture is a medium with specific and known qualities that favors the growth of a particular microorganism. The enrichment culture's environment will support the growth of a selected microorganism, while inhibiting the growth of others...

techniques. While his work on the Tobacco Mosaic Virus
Tobacco mosaic virus
Tobacco mosaic virus is a positive-sense single stranded RNA virus that infects plants, especially tobacco and other members of the family Solanaceae. The infection causes characteristic patterns on the leaves . TMV was the first virus to be discovered...

 established the basic principles of virology, it was his development of enrichment culturing that had the most immediate impact on microbiology by allowing for the cultivation of a wide range of microbes with wildly different physiologies. Winogradsky was the first to develop the concept of chemolithotrophy and to thereby reveal the essential role played by micro-organisms in geochemical processes. He was responsible for the first isolation and description of both nitrifying
Nitrifying bacteria
Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera bacteria that grow by consuming inorganic nitrogen compounds...

 and nitrogen-fixing bacteria.

Branches

The branches of microbiology can be classified into pure and applied sciences. Microbiology can be also classified based on taxonomy, in the cases of bacteriology, mycology, protozoology, and phycology. There is considerable overlap between the specific branches of microbiology with each other and with other disciplines.

Taxonomic arrangement

  • Bacteriology
    Bacteriology
    Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

    : The study of bacteria.
  • Mycology
    Mycology
    Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

    : The study of fungi.
  • Protozoology
    Protozoology
    Protozoology is the study of protozoa, the "animal-like" protists. This term has become dated as our understanding of the evolutionary relationships of the eukaryota has improved....

    : The study of protozoa.
  • Phycology
    Phycology
    Phycology is the scientific study of algae. Phycology is a branch of life science and often is regarded as a subdiscipline of botany....

     (or algology): The study of algae.
  • Parasitology
    Parasitology
    Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life...

    : The study of parasites.
  • Immunology
    Immunology
    Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

    : The study of the immune system.
  • Virology
    Virology
    Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...

    : The study of the viruses.

Integrative arrangement

  • Microbial cytology: The study of microscopic and submicroscopic details of microorganisms.
  • Microbial physiology: The study of how the microbial cell functions biochemically. Includes the study of microbial growth, microbial metabolism
    Metabolism
    Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

     and microbial cell structure
    Bacterial cell structure
    Bacteria, despite their simplicity, contain a well-developed cell structure which is responsible for many of their unique biological properties. Many structural features are unique to bacteria and are not found among archaea or eukaryotes...

    .
  • Microbial ecology
    Microbial ecology
    Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life — Eukaryota, Archaea, and Bacteria — as well as viruses....

    : The relationship between microorganisms and their environment.
  • Microbial genetics
    Microbial genetics
    Microbial genetics is a subject area within microbiology and genetic engineering. It studies the genetics of very small organisms. This involves the study of the genotype of microbial species and also the expression system in the form of phenotypes.It also involves the study of genetic processes...

    : The study of how gene
    Gene
    A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

    s are organized and regulated in microbes in relation to their cellular functions. Closely related to the field of molecular biology
    Molecular biology
    Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

    .
  • Cellular microbiology
    Cellular microbiology
    Cellular microbiology is a discipline that bridges microbiology and cell biology.The term "cellular microbiology" was coined in 1996 in a Science article...

    : A discipline bridging microbiology and cell biology
    Cell biology
    Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...

    .
  • Evolutionary microbiology: The study of the evolution of microbes. This field can be subdivided into:
    • Microbial taxonomy: The naming and classification of microorganisms.
    • Microbial systematics: The study of the diversity and genetic relationship of microorganisms.
  • Generation microbiology: The study of those microorganisms that have the same characters as their parents.

Other

  • Nano microbiology: The study of those microorganisms at nano level.
  • Exo microbiology (or Astro microbiology): The study of microorganisms in outer space.

Applied microbiology

  • Medical microbiology
    Medical microbiology
    Medical microbiology is both a branch of medicine and microbiology which deals with the study of microorganisms including bacteria, viruses, fungi and parasites which are of medical importance and are capable of causing infectious diseases in human beings...

    : The study of the pathogenic microbes and the role of microbes in human illness. Includes the study of microbial pathogenesis
    Pathogenesis
    The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent...

     and epidemiology
    Epidemiology
    Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

     and is related to the study of disease pathology
    Pathology
    Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

     and immunology
    Immunology
    Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

    .
  • Pharmaceutical microbiology
    Pharmaceutical microbiology
    Pharmaceutical microbiology is the part of industrial microbiology that is responsible for ensuring medications do not contain harmful levels of microbes- such as bacteria, yeasts and moulds.- Drug Safety :...

    : The study of microorganisms that are related to the production of antibiotics, enzymes, vitamins,vaccines, and other pharmaceutical products and that cause pharmaceutical contamination and spoil.
  • Industrial microbiology
    Industrial microbiology
    Industrial microbiology or microbial biotechnology encompasses the use of microorganisms in the manufacture of food or industrial products. The use of microorganisms for the production of food, either human or animal, is often considered a branch of food microbiology...

    : The exploitation of microbes for use in industrial processes. Examples include industrial fermentation
    Industrial fermentation
    Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...

     and wastewater treatment
    Wastewater Treatment
    Wastewater treatment may refer to:* Sewage treatment* Industrial wastewater treatment...

    . Closely linked to the biotechnology
    Biotechnology
    Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

     industry. This field also includes brewing
    Brewing
    Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...

    , an important application of microbiology.
  • Microbial biotechnology: The manipulation of microorganisms at the genetic and molecular level to generate useful products.
  • Food microbiology
    Food microbiology
    Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. Of major importance is the study of microorganisms causing food spoilage. "Good" bacteria, however, such as probiotics, are becoming increasingly important in food science...

     and Dairy microbiology: The study of microorganisms causing food spoilage and foodborne illness. Using microorganisms to produce foods, for example by fermentation.
  • Agricultural microbiology
    Agricultural microbiology
    Agricultural microbiology is a branch of microbiology dealing with plant-associated microbes and plant and animal diseases. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations....

    : The study of agriculturally relevant microorganisms. This field can be further classified into the following:
    • Plant microbiology and Plant pathology: The study of the interactions between microorganisms and plants and plant pathogens.
    • Soil microbiology
      Soil microbiology
      Soil microbiology is the study of organisms in soil, their functions, and how they affect soil properties. It is believed that between two to four billion years ago, the first ancient bacteria and microorganisms came about in Earth's primitive seas. These bacteria could fix nitrogen, in time...

      : The study of those microorganisms that are found in soil.
  • Veterinary microbiology: The study of the role in microbes in veterinary medicine
    Veterinary medicine
    Veterinary Medicine is the branch of science that deals with the prevention, diagnosis and treatment of disease, disorder and injury in non-human animals...

     or animal taxonomy
    Taxonomy
    Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

    .
  • Environmental microbiology
    Environmental microbiology
    Environmental microbiology is the study of the composition and physiology of microbial communities in the environment. The environment in this case means the soil, water, air and sediments covering the planet and can also include the animals and plants that inhabit these areas...

    : The study of the function and diversity of microbes in their natural environments. This involves the characterization of key bacterial habitats such as the rhizosphere
    Rhizosphere
    The rhizosphere is the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms. Soil which is not part of the rhizosphere is known as bulk soil. The rhizosphere contains many bacteria that feed on sloughed-off plant cells, termed rhizodeposition, and...

     and phyllosphere
    Phyllosphere
    The phyllosphere is a term used in microbiology to refer to leaf surfaces or total above-ground surfaces of a plant as a habitat for microorganisms. The below-ground microbial habitats The phyllosphere is a term used in microbiology to refer to leaf surfaces or total above-ground surfaces of a...

    , soil
    Soil
    Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

     and groundwater
    Groundwater
    Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

     ecosystem
    Ecosystem
    An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

    s, open oceans or extreme environments (extremophile
    Extremophile
    An extremophile is an organism that thrives in physically or geochemically extreme conditions that are detrimental to most life on Earth. In contrast, organisms that live in more moderate environments may be termed mesophiles or neutrophiles...

    s). This field includes other branches of microbiology such as:
    • Microbial ecology
      Microbial ecology
      Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life — Eukaryota, Archaea, and Bacteria — as well as viruses....

    • Microbially-mediated nutrient cycling
      Nutrient cycle
      A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of living matter. The process is regulated by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within ecosystems...

    • Geomicrobiology
      Geomicrobiology
      Geomicrobiology is the result of the combination of geology and microbiology. The field of geomicrobiology concerns the role of microbe and microbial processes in geological and geochemical processes and vice-versa...

    • Microbial diversity
    • Bioremediation
      Bioremediation
      Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

  • Water microbiology (or Aquatic microbiology): The study of those microorganisms that are found in water.
  • Aeromicrobiology (or Air microbiology): The study of airborne microorganisms.
  • Epidemiology
    Epidemiology
    Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

    : The study of the incidence, spread, and control of disease.

Benefits

Whilst there are undoubtedly some who fear all microbes due to the association of some microbes with various human illnesses, many microbes are also responsible for numerous beneficial processes such as industrial fermentation
Industrial fermentation
Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...

 (e.g. the production of alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

, vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 and dairy products), antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 production and as vehicles for cloning
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...

 in more complex organisms such as plants. Scientists have also exploited their knowledge of microbes to produce biotechnologically important enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s such as Taq polymerase
Taq polymerase
thumb|228px|right|Structure of Taq DNA polymerase bound to a DNA octamerTaq polymerase is a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was originally isolated by Thomas D. Brock in 1965...

, reporter gene
Reporter gene
In molecular biology, a reporter gene is a gene that researchers attach to a regulatory sequence of another gene of interest in cell culture, animals or plants. Certain genes are chosen as reporters because the characteristics they confer on organisms expressing them are easily identified and...

s for use in other genetic systems and novel molecular biology techniques such as the yeast two-hybrid system
Two-hybrid screening
Two-hybrid screening is a molecular biology technique used to discover protein–protein interactions and protein–DNA interactions by testing for physical interactions between two proteins or a single protein and a DNA molecule, respectively.The premise behind the test is the activation of...

.

Bacteria can be used for the industrial production of amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s. Corynebacterium glutamicum is one of the most important bacterial species with an annual production of more than two million tons of amino acids, mainly L-glutamate and L-lysine.

A variety of biopolymer
Biopolymer
Biopolymers are polymers produced by living organisms. Since they are polymers, Biopolymers contain monomeric units that are covalently bonded to form larger structures. There are three main classes of biopolymers based on the differing monomeric units used and the structure of the biopolymer formed...

s, such as polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

s, polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

s, and polyamide
Polyamide
A polyamide is a polymer containing monomers of amides joined by peptide bonds. They can occur both naturally and artificially, examples being proteins, such as wool and silk, and can be made artificially through step-growth polymerization or solid-phase synthesis, examples being nylons, aramids,...

s, are produced by microorganisms. Microorganisms are used for the biotechnological production of biopolymers with tailored properties suitable for high-value medical application such as tissue engineering
Tissue engineering
Tissue engineering is the use of a combination of cells, engineering and materials methods, and suitable biochemical and physio-chemical factors to improve or replace biological functions...

 and drug delivery. Microorganisms are used for the biosynthesis of xanthan, alginate, cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

, cyanophycin
Cyanophycin
Cyanophycin, or multi-L-arginyl-poly , is a non-protein, non-ribosomally produced amino acid polymer composed of an aspartic acid backbone and arginine side groups....

, poly(gamma-glutamic acid), levan
Levan
Levan can refer to:* Levan, a homopolysaccharide which is composed of D-fructofuranosyl* A group of fructans produced by bacteria or created by breaking down other kinds of plant fructans, called levan beta 2→6* The town of Levan, Utah...

, hyaluronic acid, organic acids, oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...

s and polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

, and polyhydroxyalkanoates.

Microorganisms are beneficial for microbial biodegradation
Microbial biodegradation
Interest in the microbial biodegradation of pollutants has intensified in recent years as humanity strives to find sustainable ways to clean up contaminated environments...

 or bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

 of domestic, agricultural and industrial wastes and subsurface pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 in soils, sediments and marine environments. The ability of each microorganism to degrade toxic waste
Toxic waste
Toxic waste is waste material that can cause death or injury to living creatures. It spreads quite easily and can contaminate lakes and rivers. The term is often used interchangeably with “hazardous waste”, or discarded material that can pose a long-term risk to health or environment.Toxic waste...

 depends on the nature of each contaminant. Since sites typically have multiple pollutant types, the most effective approach to microbial biodegradation
Microbial biodegradation
Interest in the microbial biodegradation of pollutants has intensified in recent years as humanity strives to find sustainable ways to clean up contaminated environments...

 is to use a mixture of bacterial species and strains, each specific to the biodegradation
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...

 of one or more types of contaminants.

There are also various claims concerning the contributions to human and animal health by consuming probiotics (bacteria potentially beneficial to the digestive system) and/or prebiotics (substances consumed to promote the growth of probiotic microorganisms).

Recent research has suggested that microorganisms could be useful in the treatment of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. Various strains of non-pathogenic clostridia
Clostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...

 can infiltrate and replicate within solid tumors. Clostridial vectors can be safely administered and their potential to deliver therapeutic proteins has been demonstrated in a variety of preclinical models.




See also

  • Archaea
    Archaea
    The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

  • Bacteria
    Bacteria
    Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

  • Biochemistry
    Biochemistry
    Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

  • Biosafety
    Biosafety
    Biosafety: prevention of large-scale loss of biological integrity, focusing both on ecology and human health .Biosafety is related to several fields:*In ecology ,...

  • Biotechnology
    Biotechnology
    Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

  • Environmental microbiology
    Environmental microbiology
    Environmental microbiology is the study of the composition and physiology of microbial communities in the environment. The environment in this case means the soil, water, air and sediments covering the planet and can also include the animals and plants that inhabit these areas...

  • Eukaryote
    Eukaryote
    A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

  • Food microbiology
    Food microbiology
    Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. Of major importance is the study of microorganisms causing food spoilage. "Good" bacteria, however, such as probiotics, are becoming increasingly important in food science...

  • Genetics
    Genetics
    Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

  • Immunology
    Immunology
    Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders ; the...

  • Important publications in microbiology

  • Industrial microbiology
    Industrial microbiology
    Industrial microbiology or microbial biotechnology encompasses the use of microorganisms in the manufacture of food or industrial products. The use of microorganisms for the production of food, either human or animal, is often considered a branch of food microbiology...

  • Iron in microbiology
    Iron in microbiology
    Iron is essential for almost all living organisms as it is involved in a wide variety of important metabolic processes. However, iron is not readily available and microorganisms therefore employ various iron uptake systems to secure sufficient supplies from their surroundings...

  • Microbial phylogenetics
    Microbial phylogenetics
    Microbial phylogenetics is the study of the evolutionary relatedness among various groups of microorganisms. The molecular approach to microbial phylogenetic analysis, pioneered by Carl Woese in the 1970s and leading to the three-domain model , revolutionized our thinking about evolution in the...

  • Medical technologist
    Medical technologist
    A Medical Laboratory Scientist is a healthcare professional who performs chemical, hematological, immunologic, microscopic, and bacteriological diagnostic analyses on body fluids such as blood, urine, sputum, stool, cerebrospinal fluid , peritoneal fluid, pericardial fluid, and synovial...

  • Medicine
    Medicine
    Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

  • Mycology
    Mycology
    Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicinals , food and entheogens, as well as their dangers, such as poisoning or...

  • Nursing
    Nursing
    Nursing is a healthcare profession focused on the care of individuals, families, and communities so they may attain, maintain, or recover optimal health and quality of life from conception to death....

  • Oral microbiology
    Oral microbiology
    Oral microbiology is the study of the microorganisms of the oral cavity and the interactions between the oral microorganisms with each other and with the host. Of particular interest is the role of oral microorganisms in the two major dental diseases: dental caries and periodontal disease.The mouth...

  • Prokaryote
    Prokaryote
    The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

  • Virology
    Virology
    Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...


Professional organizations
  • American Society for Microbiology
    American Society for Microbiology
    The American Society for Microbiology is a professional organization for scientists who study viruses, bacteria, fungi, algae, and protozoa as well as other aspects of microbiology. Microbiology is the study of organisms too small to be seen with the naked eye and which must be viewed with a...

  • Society for General Microbiology
    Society for General Microbiology
    The Society for General Microbiology is a learned society based in the United Kingdom but with members in more than 60 countries. With approximately 5000 members, it is the largest microbiological society in Europe...



Journals
  • Critical Reviews in Microbiology
    Critical Reviews in Microbiology
    Critical Reviews in Microbiology is an international, peer-reviewed academic journal that publishes comprehensive review articles covering all areas of medical microbiology. Areas covered by the journal include bacteriology, virology, microbial genetics, epidemiology, and diagnostic microbiology...

  • International Journal of Systematic and Evolutionary Microbiology
    International Journal of Systematic and Evolutionary Microbiology
    The International Journal of Systematic and Evolutionary Microbiology is a peer-reviewed scientific journal in the field of microbial systematics, first published in 1951...

  • Journal of Bacteriology
  • Nature Reviews Microbiology
    Nature Reviews Microbiology
    Launched in October 2003, Nature Reviews Microbiology is part of the Nature Publishing Group. The journal publishes reviews and perspectives that help to integrate the various disciplines, bridging fundamental research and its clinical, industrial and environmental applications to create a single...

  • Springer Protocols
    Springer Protocols
    Springer Protocols is a database of life sciences protocols published by Springer Science+Business Media. These "recipes" allow scientists to recreate experiments in their own laboratory. Springer Protocols contains about 18,000 protocols, most of which are derived from the book series Methods in...

    in Microbiology

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK