Aspergillus
Overview
Aspergillus is a genus consisting of several hundred 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...

 species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli
Pier Antonio Micheli
Pier Antonio Micheli was a noted Italian botanist, professor of botany in Pisa, curator of the Orto Botanico di Firenze, author of Nova plantarum genera iuxta Tournefortii methodum disposita...

. Viewing the fungi under a microscope, Micheli was reminded of the shape of an aspergillum
Aspergillum
An aspergillum is a liturgical implement used to sprinkle holy water. It comes in two common forms: a brush that is dipped in the water and shaken, and a perforated ball at the end of a short handle...

 (holy water sprinkler), from Latin spargere (to sprinkle), and named the genus accordingly. Today "aspergillum" is also the name of an asexual spore-forming structure common to all Aspergilli; around one-third of species are also known to have a sexual stage.
Aspergillus species are highly aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

 and are found in almost all oxygen-rich environments, where they commonly grow as 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 on the surface of a substrate, as a result of the high oxygen tension.
Encyclopedia
Aspergillus is a genus consisting of several hundred 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...

 species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli
Pier Antonio Micheli
Pier Antonio Micheli was a noted Italian botanist, professor of botany in Pisa, curator of the Orto Botanico di Firenze, author of Nova plantarum genera iuxta Tournefortii methodum disposita...

. Viewing the fungi under a microscope, Micheli was reminded of the shape of an aspergillum
Aspergillum
An aspergillum is a liturgical implement used to sprinkle holy water. It comes in two common forms: a brush that is dipped in the water and shaken, and a perforated ball at the end of a short handle...

 (holy water sprinkler), from Latin spargere (to sprinkle), and named the genus accordingly. Today "aspergillum" is also the name of an asexual spore-forming structure common to all Aspergilli; around one-third of species are also known to have a sexual stage.

Growth and distribution

Aspergillus species are highly aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

 and are found in almost all oxygen-rich environments, where they commonly grow as 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 on the surface of a substrate, as a result of the high oxygen tension. Commonly, fungi grow on carbon-rich substrates such as monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...

s (such as glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

) and polysaccharides (such as amylose
Amylose
Amylose is a linear polymer made up of D-glucose units.This polysaccharide is one of the two components of starch, making up approximately 2-30% of the structure...

). Aspergillus species are common contaminants of starchy foods (such as bread and potatoes), and grow in or on many plants and trees.

In addition to growth on carbon sources, many species of Aspergillus demonstrate oligotroph
Oligotroph
An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments...

y where they are capable of growing in nutrient-depleted environments, or environments in which there is a complete lack of key nutrients. A. niger
Aspergillus niger
Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food...

is a prime example of this; it can be found growing on damp walls, as a major component of mildew
Mildew
Mildew refers to certain kinds of molds or fungi.In Old English, it meant honeydew , and later came to mean mildew in the modern sense of mold or fungus....

.

Commercial importance

Species of Aspergillus are important medically and commercially. Some species can cause infection in humans and other animals. Some infections found in animals have been studied for years. Some species found in animals have been described as new and specific to the investigated disease and others have been known as names already in use for organisms such as saprophytes. More than 60 Aspergillus species are medically relevant pathogens. For humans there are a range of diseases such as infection to the external ear, skin lesions, and ulcers classed as mycetomas.

Other species are important in commercial microbial fermentations. For example, alcoholic beverages such as Japanese sake are often made from rice or other starchy ingredients (like manioc), rather than from grapes or malted barley. Typical microorganisms used to make alcohol, such as yeasts of the genus Saccharomyces
Saccharomyces
Saccharomyces is a genus in the kingdom of fungi that includes many species of yeast. Saccharomyces is from Greek σάκχαρ and μύκης and means sugar fungus. Many members of this genus are considered very important in food production. One example is Saccharomyces cerevisiae, which is used in making...

, cannot ferment these starches, and so koji mold such as Aspergillus oryzae
Aspergillus oryzae
Aspergillus oryzae is a filamentous fungus . It is used in Chinese and Japanese cuisine to ferment soybeans. It is also used to saccharify rice, other grains, and potatoes in the making of alcoholic beverages such as huangjiu, sake, and shōchū...

is used to break down the starches into simpler sugars.

Members of the genus are also sources of natural product
Natural product
A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...

s that can be used in the development of medications
Drug development
Drug development is a blanket term used to define the process of bringing a new drug to the market once a lead compound has been identified through the process of drug discovery...

 to treat human disease.

Perhaps the largest application of Aspergillus niger is as the major source of citric acid
Citric acid
Citric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks...

; this organism accounts for over 99% of global citric acid production, or more than 1.4 million tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

s per annum. A. niger is also commonly used for the production of native and foreign enzymes, including glucose oxidase
Glucose oxidase
The glucose oxidase enzyme is an oxido-reductase that catalyses the oxidation of glucose to hydrogen peroxide and D-glucono-δ-lactone. In cells, it aids in breaking the sugar down into its metabolites....

 and hen egg white lysozyme
Lysozyme
Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are glycoside hydrolases, enzymes that damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between...

. In these instances, the culture is rarely grown on a solid substrate, although this is still common practice in Japan, but is more often grown as a submerged culture in a bioreactor
Bioreactor
A bioreactor may refer to any manufactured or engineered device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical process is carried out which involves organisms or biochemically active substances derived from such organisms. This...

. In this way, the most important parameters can be strictly controlled, and maximal productivity can be achieved. It also makes it far easier to separate the chemical or enzyme of importance from the medium, and is therefore far more cost-effective.

Research

A. nidulans
Aspergillus nidulans
Aspergillus nidulans is one of many species of filamentous fungi in the phylum Ascomycota...

has been used as a research organism for many years and was used by Guido Pontecorvo
Guido Pontecorvo
Guido Pontecorvo ForMemRS was an Italian-born geneticist.-Career:He fled to Britain in 1938.* Institute of Animal Genetics, University of Edinburgh, 1938-40 and 1944-45...

 to demonstrate parasexuality in fungi. Recently, A. nidulans was one of the pioneering organisms to have its genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

 sequenced by researchers at the Broad Institute
Broad Institute
The Broad Institute is a genomic medicine research center located in Cambridge, Massachusetts, United States. Although it is independently governed and supported as a 501 nonprofit research organization, the institute is formally affiliated with the Massachusetts Institute of Technology, Harvard...

. As of 2008, a further seven Aspergillus species have had their genomes sequenced: the industrially useful A. niger
Aspergillus niger
Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food...

(two strains), A. oryzae
Aspergillus oryzae
Aspergillus oryzae is a filamentous fungus . It is used in Chinese and Japanese cuisine to ferment soybeans. It is also used to saccharify rice, other grains, and potatoes in the making of alcoholic beverages such as huangjiu, sake, and shōchū...

and A. terreus
Aspergillus terreus
Aspergillus terreus is a fungus commonly used in industry to produce important organic acids, such as itaconic acid and cis-aconitic acid. It was also the initial source for the drug mevinolin , a drug for lowering serum cholesterol. A. terreus may cause opportunistic infection in people with...

, and the pathogens A. clavatus
Aspergillus clavatus
Aspergillus clavatus is a species of Aspergillus with conidia dimensions 3-4.5 x 2.5-4.5 micrometres. It is found in soil and animal manure...

, A. fischerianus
Aspergillus fischerianus
Aspergillus fischerianus is a plant pathogen.- External links :**...

(Neosartorya fischeri), A. flavus
Aspergillus flavus
Aspergillus flavus is a fungus. It is a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce...

and A. fumigatus
Aspergillus fumigatus
Aspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in individuals with an immunodeficiency....

(two strains). A. fischerianus is hardly ever pathogenic but is very closely related to the common pathogen A. fumigatus; it was sequenced in part to better understand A. fumigatus pathogenicity.

Genomics

The simultaneous publication of three Aspergillus genome manuscripts in Nature in December 2005 established Aspergillus as the leading filamentous fungal genus for comparative genomic studies. Like most major genome projects, these Aspergillus efforts were collaborations between a large sequencing centre and the respective community of scientists. For example, the Institute for Genome Research (TIGR) worked with the Aspergillus fumigatus community. A. nidulans was sequenced at the Broad Institute. A. oryzae was sequenced in Japan at the National Institute of Advanced Industrial Science and Technology. The Joint Genome Institute ( JGI) of the Department of Energy has released sequence data for a citric acid-producing strain of A. niger. TIGR, now re-named the Venter Institute is currently spear-heading a project on the A. flavus genome.

Genome sizes for sequenced species of Aspergillus range from approximately 29.3 Mb for A. fumigatus to 37.1 Mb for A. oryzae while the numbers of predicted genes vary from approximately 9926 for A. fumigatus to approximately 12,071 for A. oryzae. The genome size of an enzyme producing strain of A. niger is of intermediate size at 33.9 Mb.

Pathogens

Some Aspergillus species cause serious disease in humans and animals. The most common causing pathogenic species are Aspergillus fumigatus
Aspergillus fumigatus
Aspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in individuals with an immunodeficiency....

and Aspergillus flavus
Aspergillus flavus
Aspergillus flavus is a fungus. It is a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce...

. Aspergillus flavus
Aspergillus flavus
Aspergillus flavus is a fungus. It is a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce...

produces
aflatoxin
Aflatoxin
Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, the most notable ones being Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known...

 which is both a toxin and a carcinogen, and which can contaminate foods such as nuts. The most common causing allergic disease are Aspergillus fumigatus and Aspergillus clavatus
Aspergillus clavatus
Aspergillus clavatus is a species of Aspergillus with conidia dimensions 3-4.5 x 2.5-4.5 micrometres. It is found in soil and animal manure...

. Other species are important as agricultural pathogens. Aspergillus spp. cause disease on many grain crops, especially maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

, and synthesize mycotoxin
Mycotoxin
A mycotoxin is a toxic secondary metabolite produced by organisms of the fungus kingdom, commonly known as molds. The term ‘mycotoxin’ is usually reserved for the toxic chemical products produced by fungi that readily colonize crops...

s including aflatoxin
Aflatoxin
Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, the most notable ones being Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known...

.

Aspergillosis

Aspergillosis
Aspergillosis
Aspergillosis is the name given to a wide variety of diseases caused by fungi of the genus Aspergillus. The most common forms are allergic bronchopulmonary aspergillosis, pulmonary aspergilloma and invasive aspergillosis. Most humans inhale Aspergillus spores every day...

 is the group of diseases caused by Aspergillus. The most common subtype among paranasal sinus infections associated with aspergillosis is Aspergillus fumigatus. The symptoms include fever, cough, chest pain or breathlessness, which also occur in many other illnesses so diagnosis can be difficult. Usually, only patients with already weakened immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

s or who suffer other lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

 conditions are susceptible.

In humans, the major forms of disease are:
  • Allergic bronchopulmonary aspergillosis or ABPA, which affects patients with respiratory diseases like asthma
    Asthma
    Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

    , cystic fibrosis
    Cystic fibrosis
    Cystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...

    , and sinusitis
    Sinusitis
    Sinusitis is inflammation of the paranasal sinuses, which may be due to infection, allergy, or autoimmune issues. Most cases are due to a viral infection and resolve over the course of 10 days...

    ).
  • Acute invasive aspergillosis, a form that grows into surrounding tissue, more common in those with weakened immune system
    Immune system
    An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

    s such as AIDS
    AIDS
    Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

     or chemotherapy
    Chemotherapy
    Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....

     patients.
  • Disseminated invasive aspergillosis, an infection spread widely through the body.
  • Aspergilloma
    Aspergilloma
    An aspergilloma, also known as a mycetoma or fungus ball, is a clump of fungus which exists in a body cavity such as the lung. It is associated with the Aspergillus species, but Zygomycota and Fusarium may also form similar structures....

    , a "fungus ball" that can form within cavities such as the lung
    Lung
    The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...



Aspergillosis of the air passages is also frequently reported in birds, and certain species of Aspergillus have been known to infect insects.

See also

  • Mycotoxin
    Mycotoxin
    A mycotoxin is a toxic secondary metabolite produced by organisms of the fungus kingdom, commonly known as molds. The term ‘mycotoxin’ is usually reserved for the toxic chemical products produced by fungi that readily colonize crops...

  • Sick building syndrome
    Sick building syndrome
    Sick building syndrome is a combination of ailments associated with an individual's place of work or residence. A 1984 World Health Organization report into the syndrome suggested up to 30% of new and remodeled buildings worldwide may be linked to symptoms of SBS...

     (SBS)
  • Mold health issues

External links

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