My.co.plas'ma. Gr. masc. n.
myces
a fungus; Gr. neut. n.
plasma
something formed or molded, a form; N.L. neut. n.
Mycoplasma
fungus form.
Tenericutes / Mollicutes / Mycoplasmatales / Mycoplasmataceae / Mycoplasma
Bacteria in the genus
Mycoplasma
are small (300–800 nm in diameter) pleomorphic cells devoid of a cell wall. Culturable species usually form very small (<1 mm) umbonate colonies on agar. Their use of the codon
UGA
to encode tryptophan is a distinctive characteristic of all species examined to date. As a consequence of their small (usually 0.5–1.5 Mb) genomes they have limited intermediary metabolism and are nutritionally fastidious, requiring exogenous sugars or arginine, cholesterol or other sterols, peptides, and free nucleic acids for axenic growth. In nature, all species are obligate commensals or parasites with varying degrees of specificity for a wide range of vertebrate hosts. The type species
Mycoplasma mycoides
subsp.
mycoides
and
Mycoplasma capricolum
subsp.
capripneumoniae
are highly virulent animal pathogens subject to strict international regulations, but the genus is perhaps better known for
Mycoplasma pneumoniae
, the agent of primary atypical “walking” pneumonia in humans. The relative biological simplicity of mycoplasmas confers significant advantages for current proteomics, metabolomics, synthetic genomics, and systems biology research. For example, the recent chemical synthesis and transplantation of intact chromosomes demonstrated that it is possible to enliven a mycoplasma fully capable of autonomous replication with an artificially constructed genome.
DNA
G
+
C content
(
mol
%): 23–40.
Type species
:
Mycoplasma mycoides
(Borrel, Dujardin‐Beaumetz, Jeantet and Jouan 1910) Freundt 1955, 73 (
Asterococcus mycoides
Borrel, Dujardin‐Beaumetz, Jeantet and Jouan 1910, 179).