Phenotypic switching in mycoplasmas: phase variation of diverse surface lipoproteins.

The ability of some microorganisms to rapidly alter the expression and structure of surface components reflects an important strategy for adaptation to changing environments, including those encountered by infectious agents within respective host organisms. Mycoplasma hyorhinis, a wall-less prokaryotic pathogen of the class Mollicutes, is shown to undergo high-frequency phase transitions in colony morphology and opacity and in the expression of diverse lipid-modified, cell-surface protein antigens. These proteins spontaneously vary in size, contain highly repetitive structures, and are oriented with their carboxyl-terminal region external to the membrane. Thus, mycoplasma membrane lipoproteins generate microbial surface diversity and may be part of a complex system that controls interactions of these organisms with their hosts.