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Micrococcus mucilaginosis 01.png
Micrococcus mucilaginosis
Scientific classification
Kingdom: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Subclass: Actinobacteridae
Order: Actinomycetales
Suborder: Micrococcineae
Family: Micrococcaceae
Genus: Micrococcus
Cohn 1872

Micrococcus aloeverae
Micrococcus antarcticus
Micrococcus cohnii
Micrococcus endophyticus
Micrococcus flavus
Micrococcus lactis
Micrococcus luteus
Micrococcus lylae
Micrococcus mucilaginosis
Micrococcus roseus
Micrococcus terreus
Micrococcus mortus
Micrococcus yunnanensis

Micrococcus (mi’ krō kŏk’ Əs) is a genus of bacteria in the Micrococcaceae family. Micrococcus occurs in a wide range of environments, including water, dust, and soil. Micrococci have Gram-positive spherical cells ranging from about 0.5 to 3 micrometers in diameter and typically appear in tetrads. They are catalase positive, oxidase positive, indole negative and citrate negative. Micrococcus has a substantial cell wall, which may comprise as much as 50% of the cell mass. The genome of Micrococcus is rich in guanine and cytosine (GC), typically exhibiting 65 to 75% GC-content. Micrococci often carry plasmids (ranging from 1 to 100 MDa in size) that provide the organism with useful traits.


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 when grown on toxic organic pollutants like pyridine.[1] Hybridization studies indicate that species within the genus Micrococcus are not closely related, showing as little as 50% sequence similarity. This suggests that some Micrococcus species may, on the basis of ribosomal RNA analysis, eventually be re-classified into other microbial genera.


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 mesophiles; some, like Micrococcus antarcticus (found in Antarctica) are psychrophiles.

Though not a spore 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.[citation needed] Recent work by Greenblat et al. demonstrates 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.[2]


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, such as HIV patients.[3] 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[edit]

Micrococci, like many other representatives of the Actinobacteria, can be catabolically versatile, with the ability to utilize a wide range of unusual substrates, such as pyridine, herbicides, chlorinated biphenyls, and oil.[4][5] They are likely involved in detoxification or biodegradation of many other environmental pollutants.[6] Other Micrococcus isolates produce various useful products, such as long-chain (C21-C34) aliphatic hydrocarbons for lubricating oils.

Micrococcus mortus[edit]

The most recent strand of micrococci to be discovered is the "Micrococcus mortus". It has distinctive structure that differs from the most common strand of Micrococcus: with a larger/flatter face to each strand; the Micrococcus mortus holds a far larger surface area to volume ratio to normal strands. It is particularly prominent in HIV patients as it is a strain that is particularly difficult to provide effective antibiotic treatment for as it is a highly frequent mutator.


  1. ^ Sims GK, Sommers LE, Konopka A (1986). "Degradation of Pyridine by Micrococcus luteus Isolated from Soil". Appl Environ Microbiol 51 (5): 963–968. PMC 238995. PMID 16347070. 
  2. ^ Greenblat, C.L., Baum, J., Klein, B.Y., Nachshon, S., Koltunov, V., Cano, R.J. (2004). "Micrococcus luteus – Survival in Amber". Microbial Ecology 48 (1): 120–127. doi:10.1007/s00248-003-2016-5. PMID 15164240. 
  3. ^ Smith K, Neafie R, Yeager J, Skelton H (1999). "Micrococcus folliculitis in HIV-1 disease". Br J Dermatol 141 (3): 558–61. doi:10.1046/j.1365-2133.1999.03060.x. PMID 10583069. 
  4. ^ Doddamani H, Ninnekar H (2001). "Biodegradation of carbaryl by a Micrococcus species". Curr Microbiol 43 (1): 69–73. doi:10.1007/s002840010262. PMID 11375667. 
  5. ^ Sims GK, O'loughlin EJ (1992). "Riboflavin Production during Growth of Micrococcus luteus on Pyridine". Appl Environ Microbiol 58 (10): 3423–3425. PMC 183117. PMID 16348793. 
  6. ^ Zhuang W, Tay J, Maszenan A, Krumholz L, Tay S (2003). "Importance of Gram-positive naphthalene-degrading bacteria in oil-contaminated tropical marine sediments". Lett Appl Microbiol 36 (4): 251–7. doi:10.1046/j.1472-765X.2003.01297.x. PMID 12641721. 

Microbewiki at Kenyon College