Extramembranous structure in mycoplasmas.

Abstract

The murein sacculus surrounds the inner membrane of most prokaryotes giving shape and stability to the organism (Costerton and Irvin, 1981). It is composed of peptidoglycan, a polymer of carbohydrates and amino acids. In Chlamydia, the outer surface is composed of a rigid, disulfide-interlocked protein layer which replaces the function of the peptidoglycan layer. In these organisms, the degree of cross-linking coincides with differentiation from a metabolically inactive, extracellular elementary body to a metabolically active, pleomorphic, intracellular reticulate body (Hackstadt et al., 1985). Mollicutes, however, lack cell walls, peptidoglycan and protein matrices (Plackett, 1959). Their single membrane must serve to separate cytoplasmic components from the environment, provide shape, and prevent lysis under changing environmental conditions. In this respect their membrane more closely resembles eukaryotic membranes than other eubacteria. It is a single cholesterol-containing phospholipid bilayer to which is attached or embedded a variety of proteins and carbohydrates. The exact nature of the outer surface of mycoplasmas, except for the protein component which has been studied extensively in many species, is not known, and variations occur as a consequence of environmental or genetic changes (Rosengarten and Wise, 1990; Watson et al., 1988).KeywordsUreaplasma UrealyticumMycoplasma SpeciesMycoplasma HominisBronchiolar EpitheliumBovine Respiratory DiseaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.