Micrococcus characteristics, morphology, diseases

Robert Johnston

Micrococcus It is a genus of bacteria that is a normal part of the human body's microbiota. Likewise, it is located in a large number of environments spread throughout the world. They are commensals of the human being, which implies that they obtain benefits, but do not harm the individual.

This genus encompasses five species: Micrococcus antarcticus, Micococcus luteus, Micrococcus mucilaginosis Y Micrococcus roseus. Of these, only one is recognized as a pathogen, the Micrococcus luteus, since it has been related to pathologies such as endocarditis.

Micrococcus luteus

It is an opportunistic microorganism, that is, it becomes pathogenic when the conditions of the individual's immune system change and it weakens. Mycobacterium infections are common in people who are HIV positive, with conditions such as leukemia, or who have received an organ transplant..

Likewise, these bacteria have the peculiarity that they can use a great variety of substrates to use them in chemical reactions. Among those substrates, herbicides, pyridine and petroleum can be mentioned. This capacity is of great help in cleaning and environmental decontamination.

Article index

  • 1 Taxonomy
  • 2 Morphology
  • 3 General characteristics
  • 4 Diseases
    • 4.1 Endocarditis
    • 4.2 Pneumonia
    • 4.3 Septic shock
  • 5 Treatment
  • 6 References


The taxonomic classification of the genus Micrococcus is the next:

Domain: Bacterium

Edge: Actinobacteria

Class: Actinobacteria

Subclass: Actinobacteridae

Order: Actinomycetales

Suborder: Micrococcineae

Family: Micrococcaceae

Gender: Micrococcus.


Bacteria of the genus Micrococcus They are coconuts, that is, they have a rounded shape. They are approximately 0.5 - 3.5 microns in diameter. They are united in pairs, tetrads (groups of 4) or clusters.

They present carotenoid pigments, which makes them manifest colors such as yellow, red or orange.

General characteristics

They are catalase and oxidase positive

Bacteria belonging to the genus Micrococcus are capable of unfolding the hydrogen peroxide molecule (HtwoORtwo) in water and oxygen, thanks to the fact that they can synthesize the enzyme catalase, which is what catalyzes this reaction.

Similarly, they synthesize another extremely important enzyme, oxidase. This enzyme is responsible for catalyzing oxide reduction reactions in which oxygen acts as an electron acceptor.

These two enzymes constitute a parameter to differentiate some bacteria from others. In the case of catalase, the appearance of bubbles indicates that there is the presence of catalase. While the appearance of an intense blue color indicates that there was an oxidation reaction and therefore the oxidase enzyme is present.

May reduce nitrates

These bacteria can transform nitrates into nitrites, through a reduction process catalyzed by the enzyme nitrate reductase. The chemical reaction is as follows:

NOT3 + 2e- + 2H - NOtwo + HtwoOR

They are strict aerobes

Bacteria of the genus Micrococcus require oxygen to carry out various processes. That is why they must be developed in environments that have a wide availability of this element..


These bacteria have been isolated from various habitats. They have been found in water, soil, and dust. It is also present in human skin, dairy products and beer..

Bacteria of the genus Micrococcus are commensal of certain mucous membranes, the oropharynx, and the skin..

They are gram positive

Due to the peptidoglycan that is in the cell wall, these bacteria, when subjected to the Gram staining process, acquire a violet color. This is because peptidoglycan retains dye particles thanks to its structure..

They are heat resistant

These bacteria belong to the group of heat resistant ones, since despite the fact that their optimum growth temperature is between 25 and 30 ° C, it has been found that they have grown at temperatures below 10 ° C.

They do not form spores

Bacteria of this genus do not contemplate the formation of spores in their life cycle. However, despite this, bacterial cells are able to survive for long periods, even when environmental conditions are hostile..


Although this genus is associated with some pathology on very few occasions, it is sometimes the cause of certain pathologies, some milder than others.

This bacterium is opportunistic, which means that it becomes a pathogen in people in whom the immune system is weakened, for example people who are HIV positive or have undergone a transplant..

Of course, the pathogenesis of the genus will be specific for each of the species that make it up..

The Micrococcus luteus, a famous member of this genus of bacteria, often associated with opportunistic pathologies in people with weak immune systems.

Among the diseases with which bacteria of the genus have been associated Micrococcus can be counted:

  • Endocarditis
  • Pneumonia
  • Septic shock


It is the inflammation of the inner layer of the heart, especially of the atrioventricular valves, product of colonization by bacterial cells of the genus Micrococcus.

This pathology presents symptoms such as fever, chills, shortness of breath and fatigue, among others..

The Micrococcus They are not the only bacteria that can cause endocarditis. Many other bacteria that are part of the normal microbiota of the body can enter the blood and reach the heart.


It is an infection at the level of the pulmonary alveoli, as a consequence of invasion by the Micrococcus.

The symptoms of pneumonia are varied, but the most common are fever, cough with phlegm, excessive sweating and pain to breathe.

Septic shock

It is a pathology that occurs when an infection spreads throughout the body and results in an excessive decrease in blood pressure. It can occur for multiple causes, one of them being infection by Micrococcus.

The symptoms of septic shock are systemic, that is, they do not affect a single organ but the general functioning of the body. Symptoms include: elevated or decreased temperature, palpitations, feeling dizzy, rapid heartbeat, paleness, and shortness of breath.


Because the Micrococcus is a bacterium, the appropriate treatment is the use of antibiotic therapy.

Bacteria of this genus have been determined to be sensitive to vancomycin, penicillin, gentamicin, and cindamycin. Because of this, they are the antibiotics that are generally selected to treat conditions caused by these bacteria..


  1. Albertson, D., Natsios, G. and Glekman, R. (1978). Septic shock with Micrococcus luteus. Archive internal medicine. 138 (3) 487-488
  2. Gender Micrococcus. Obtained from: diversitymicrobiana.com
  3. Kokur, M., Kloos, W. and Heinz, K. (2017). The genus Micrococcus. The Prokaryotes. 961-971
  4. Kooken, J., Fox, K. and Fox, A. (2012). Characterization of Micrococcus strains isolated from indoor air. Mol Cell Probes. 26 (1). 1-5
  5. Retrieved from: catalog.hardydiagnostics.com
  6. Retrieved from: microbewiki.com
  7. Micrococcus sp. Retrieved from: msdsonline.com

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