TAXONOMY: Bacteria -> Terrabacteria group -> Tenericutes -> Mollicutes -> Mycoplasmatales -> Mycoplasmataceae -> Mycoplasma
Pleomorphic cells, 300–800 nm in diameter, varying in shape from spherical, ovoid or flask-shaped, or twisted rods, to slender branched filaments ranging in length from 50 to 500 nm. Cells lack a cell wall and are bounded by a single plasma membrane. Gram-stain-negative due to the absence of a cell wall. Some have a complex internal cytoskeleton. Some have a specific tip structure that mediates attachment to host cells or other surfaces. Usually nonmotile, but gliding motility has been demonstrated in some species. Aerobic or facultatively anaerobic. Optimum growth at 37°C is common, but permissive growth temperatures range from 20 to 45°C. Chemo-organotrophic, usually using either sugars or arginine as the major energy source. Require cholesterol or related sterols for growth. Colonies are usually less than 1 mm in diameter. The typical colony has a fried-egg appearance. The genome size of species examined ranges from 580 kbp to about 1350 kbp. The codon UGA encodes tryptophan in all species examined. Commensals or pathogens in a wide range of vertebrate hosts.
DNA G+C content (mol%): 23–40.
Type species: Mycoplasma mycoides
This genus contains microbial species that can reside in the human gastrointestinal tract. [PMC 4262072]