Ureaplasma urealyticum in the context of "Mollicutes"

Mollicutes is a class of bacteria distinguished by the absence of a cell wall and its peptidoglycan. The word Mollicutes is derived from Latin mollis 'soft, pliable' and cutis 'skin'. Individuals are very small, typically only 0.2–0.3 μm (200–300 nm) in size and have a very small genome size. They vary in form, although most have sterols that make the cell membrane somewhat more rigid. Many move about by gliding, but members of the genus Spiroplasma are helical and move by twisting. The best-known genus in the Mollicutes is Mycoplasma, though it has been split in 2018 into several genera. Colonies show the typical "fried-egg" appearance.

Mollicutes can be parasitic or saprotrophic. They can be parasites of various animals and plants, living on or in the host's cells. Many cause diseases in humans, attaching to cells in the respiratory or urogenital tracts, particularly species of Mycoplasma and Ureaplasma. Phytoplasma and Spiroplasma are plant pathogens associated with insect vectors.