Mycoplasma

DEFINITION
Class Mollicutes (Latin, mollis, “soft”; cutis, “skin”); > 80 genera; three families: mycoplasmas, T-mycoplasmas or ureaplasmas, and acholeplasmas
Smallest (0.2–0.3 mm) and simplest procaryotic cells capable of self-replication
Fastidious, facultative anaerobic, gramnegative rods
Lack a cell wall; thus plastic, highly pleomorphic, and sensitive to lysis by osmotic shock, detergents, alcohols, and specific antibody plus complement; enclosed by a trilayered cell membrane built of amphipathic lipids (phospholipids, glycolipids, lipoglycans, sterols) and proteins; most require sterols for growth.
Different from wall-defective or wall-less L-form bacteria, which can revert to the normal cell wall strain
Reproduce by binary fission; genome replication not necessarily synchronized with cell division, resulting in budding forms and chains of beads
Ubiquitous in nature as parasites, commensals, or saprophytes in animals, plants, and insects; many are pathogens of humans, animals, plants, and insects.