Mycoplasma incognitus

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A Microbial Biorealm page on the genus Mycoplasma incognitus


Higher order taxa

Bacteria; Tenericutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma


Mycoplasma fermentans (incognitus strain)

Description and significance

Mycoplasma incognitus is a human cell invasive mycoplasma and a disease agent that can cause a variety of human diseases including AIDS, Chronic Fatigue Syndrome, Type 1 Diabetes, Parkinson's Disease, and Rheumatoid Arthritis [3]. M. incognitus belongs to the Bacterial Domain and is thought to be a mutated form of the Brucella bacterium combined with the Visna virus, from which the mycoplasma is extracted [4]. M. incognitus is an immunomodulatory agent, which means it can alter the immune response by reducing the ability of the immune system to produce antibodies [3]. This mycoplasma is highly pathogenic and can be passed from person to person via bodily fluids.

Genome structure

As mycoplasmas in general have evolved, they have lost considerable portions of their ancestor's chromosomes but retained the genes essential for life [2]. That being said, Mycoplasma incognitus acts as a parasite and gains most of its nutrients from its host because it has a very small genome consisting of only the genes essential for life. It is estimated that M. incognitus has less than 500 genes and could have a genome as small as 600 kb [2]. The genome has not yet been sequenced.

Cell and Colony Structure

There have been frequent unsuccessful attempts at isolating a culture of M. incognitus because it is more fastidious in cultivation requirements than M. fermentans. M. incognitus is only able to grow on sp-4 modified medium and grows very slowly. The colonies are irregular and very small with diffuse edges, with occasional filamentous morphology. It is known that the most frequently colonized sites are epithelial cell surfaces and red and white blood cells [1].


Scientists have found that M. incognitus can utilize glucose both aerobically and anaerobically, but prefers to utilize the alternate energy source: fructose. The metabolism of sugars may play an important role in the pathological process of infection but scientists are not sure how yet. M. incognitus can metabolize arginine and scientists believe that it is possible that mycoplasmas that utilize arginine may be more pathogenic than those that don't [3].


M. incognitus is an obligate pathogen and cannot survive unless it is inside a host.


M. incognitus is an immunomodulatory agent that can alter the immune response by reducing the immune system's ability to produce antibodies [3]. This mycoplasma acts by entering into the individual cells of the body where it can lie dormant for 10, 20, or 30 years. If a trauma occurs or a vaccination isn't successful, M. incognitus can become triggered and start invading and destroying certain cells, depending on the individual's genetic predisposition. M.incognitus has the ability to alter red blood cells so that they swell and therefore cannot be compressed and passed through the capillaries [4]. The mycoplasma is also able to stimulate or suppress lymphocytes in a polyclonal manner both in vitro and in vivo, and modulate the activities of monocytes, macrophages, and NK cells [2].

It has also been shown that the lipid-associated membrane proteins of Mycoplasma incognitus can activate the long terminal repeats of HIV through toll-like receptors [2]. The mechanism is still being studied.


[1] Campo, Laura et al. (1998) Genotypic and Phenotypic Analysis of Mycoplasma fermentans Strains Isolated From Different Host Tissues J Clin Microbiol. 36(5): 1371-1377

[2] Razin, Shmuel, Yogev, David and Naot, Yehudith (1998) Molecular Biology and Pathogenicity of Mycoplasmas Microbial Mol Biol Rev. 62(4): 1094-1156

[3] Schaeverbeke, Thierry et al. (1998) Genotypic Characterization of Seven Strains of Mycoplasma fermentans Isolated From Synovial Fluids of Patients With Arthritis J Clin Microbiol. 36(5): 1226-1231

[4] Scott, Donald W. (2001) Mycoplasma and Neurosystemic Diseases Nexus Magazine vol. 8 #5

Edited by Keisha Picknell of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences,