Micrococcus
Overview
 
Micrococcus is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of 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...

 in the Micrococcaceae
Micrococcaceae
The family Micrococcaceae includes bacterial genera of Gram positive cocci that inhabit the air and skin such as Micrococcus luteus.-External links:* * J.P. Euzéby's...

 family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

. Micrococcus occurs in a wide range of environments, including water, dust, and soil. Micrococci have Gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 spherical cells ranging from about 0.5 to 3 micrometers in diameter and are typically appear in tetrads. Micrococcus has a substantial cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

, which may comprise as much as 50% of the cell mass. The genome of Micrococcus is rich in guanine
Guanine
Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...

 and cytosine
Cytosine
Cytosine is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine . It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached . The nucleoside of cytosine is cytidine...

 (GC), typically exhibiting 65 to 75% GC-content
GC-content
In molecular biology and genetics, GC-content is the percentage of nitrogenous bases on a DNA molecule that are either guanine or cytosine . This may refer to a specific fragment of DNA or RNA, or that of the whole genome...

.
Encyclopedia
Micrococcus is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of 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...

 in the Micrococcaceae
Micrococcaceae
The family Micrococcaceae includes bacterial genera of Gram positive cocci that inhabit the air and skin such as Micrococcus luteus.-External links:* * J.P. Euzéby's...

 family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

. Micrococcus occurs in a wide range of environments, including water, dust, and soil. Micrococci have Gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 spherical cells ranging from about 0.5 to 3 micrometers in diameter and are typically appear in tetrads. Micrococcus has a substantial cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

, which may comprise as much as 50% of the cell mass. The genome of Micrococcus is rich in guanine
Guanine
Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...

 and cytosine
Cytosine
Cytosine is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine . It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached . The nucleoside of cytosine is cytidine...

 (GC), typically exhibiting 65 to 75% GC-content
GC-content
In molecular biology and genetics, GC-content is the percentage of nitrogenous bases on a DNA molecule that are either guanine or cytosine . This may refer to a specific fragment of DNA or RNA, or that of the whole genome...

. Micrococci often carry plasmid
Plasmid
In microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...

s (ranging from 1 to 100MDa in size) that provide the organism with useful traits.

Species

Some species of Micrococcus, such as M. luteus (yellow) and M. roseus (red) produce yellow or pink colonies when grown on mannitol salt agar. Isolates of M. luteus have been found to overproduce riboflavin
Riboflavin
Riboflavin, also known as vitamin B2 or additive E101, is an easily absorbed micronutrient with a key role in maintaining health in humans and animals. It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. As such, vitamin B2 is required for a...

 when grown on toxic organic pollutants like pyridine. Hybridization studies indicate that species within the genus Micrococcus are not closely related, showing as little as 50% sequence homology. This suggests that some Micrococcus species may, on the basis of ribosomal RNA
Ribosomal RNA
Ribosomal ribonucleic acid is the RNA component of the ribosome, the enzyme that is the site of protein synthesis in all living cells. Ribosomal RNA provides a mechanism for decoding mRNA into amino acids and interacts with tRNAs during translation by providing peptidyl transferase activity...

 analysis, eventually be re-classified into other microbial genera.

Environmental

Micrococci have been isolated from human skin, animal and dairy products, and beer. They are found in many other places in the environment, including water, dust, and soil. M. luteus on human skin transforms compounds in sweat into compounds with an unpleasant odor. Micrococci can grow well in environments with little water or high salt concentrations. Most are mesophile
Mesophile
A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 25 and 40 °C...

s; some, like Micrococcus antarcticus (found in Antarctica) are psychrophile
Psychrophile
Psychrophiles or cryophiles are extremophilic organisms that are capable of growth and reproduction in cold temperatures, ranging from −15°C to +10°C. Temperatures as low as −15°C are found in pockets of very salty water surrounded by sea ice. They can be contrasted with thermophiles, which...

s.

Though not a spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

 former, Micrococcus cells can survive for an extended period of time: unprotected cultures of soil micrococci have been revived after storage in a refrigerator for 10 years. Recent work by Greenblat et al. demonstrate that Micrococcus luteus has survived for at least 34,000 to 170,000 years on the basis of 16S rRNA analysis, and possibly much longer.

Pathogenesis

Micrococcus is generally thought to be a saprotrophic or commensal organism, though it can be an opportunistic pathogen, particularly in hosts with compromised immune systems
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...

, such as HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

 patients. It can be difficult to identify Micrococcus as the cause of an infection, since the organism is a normally present in skin microflora, and the genus is seldom linked to disease. In rare cases, death of immunocompromised patients has occurred from pulmonary infections caused by Micrococcus. Micrococci may be involved in other infections, including recurrent bacteremia, septic shock, septic arthritis, endocarditis, meningitis, and cavitating pneumonia (immunosuppressed patients).

Industrial uses

Micrococci, like many other representatives of the Actinobacteria, can be catabolically
Catabolism
Catabolism is the set of metabolic pathways that break down molecules into smaller units and release energy. In catabolism, large molecules such as polysaccharides, lipids, nucleic acids and proteins are broken down into smaller units such as monosaccharides, fatty acids, nucleotides, and amino...

 versatile, with the ability to utilize a wide range of unusual substrates, such as pyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

, herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

s, chlorinated biphenyls, and oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

. They are likely involved in detoxification or biodegradation of many other environmental pollutants. Other Micrococcus isolates produce various useful products, such as long-chain (C21-C34) aliphatic hydrocarbons for lubricating oils.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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