Heterogeneity of mycoplasmal lipids.

Abstract

The physical and chemical structures of mycoplasmal lipids are significant in that some are antigenic determinants, they determine the physical structure and permeability of the limiting membrane, and they may provide insight into the origins of mycoplasmas. Those lipids that impart specificity to antigens are haptenic in character and may be components of immunizing antigens. The most likely candidates for this phenomenon are the glycolipids, since variations in the type of monosaccharide, the type of linkage between the sugars, and the number of sugar units provide for a wide range of antigenic types. A parallel can be seen with the O antigens of enteric bacteria. Certain lipids appear specific for certain genera of microorganisms that fit well into taxonomic groups defined by classical methods [1]. Other lipids have components or complete structures found in biopolymers, suggesting a possible role as biosynthetic precursors. The structure of some or all of the lipids have been determined for seven species of Mycoplasma that represent different physiologic and pathogenic types. Table 1 lists the known lipids for these species. Certain aspects need to be singled out and enlarged upon. All species examined contain phosphatidyl glycerol or some derivative of it. In many this is the predominant lipid, while in others it is a minor component. This type of lipid is ubiquitous among all living organisms. Those mycoplasmas that possess a nutritional requirement for sterol contain sterol of identical structure to that supplied exogenously. At this point the similarities cease.