PROPERTIES OF ADHERING AND NONADHERING POPULATIONS OF MYCOPLASMA-GENITALIUM

The interaction between Mycoplasma genitalium and human lung fibroblas ts (HLFs) was studied with the use of wild-type and hemadsorption-nega tive (HA-) mycoplasmas. S-35!methionine-labeled M. genitalium adhered to HLFs by first-order kinetics, with maximal interaction occurring a t approximately 2 hours. Electron microscopy of chemically fixed cells revealed an almost immediate association of mycoplasmas with the HLF plasma membrane that was mediated by the mycoplasma tip and a nap-like layer, which appeared to extend from the tip around much of the mycop lasmal unit membrane. Following cytadherence, M. genitalium appeared c apable of invading the intracellular spaces of targeted HLF cells, pos sibly by receptor-mediated endocytosis. Spontaneously arising HA- vari ants of M. genitalium strain G37 failed to adhere to HLF cells and wer e distinguished on the basis of their protein profiles. SDS-PAGE analy sis of the class I (lacking the 140-kd protein but containing a polype ptide doublet at approximately 140-kd) and class II (lacking the 140-k d protein and doublet) variants of M. genitalium revealed that class I variants contain a doublet protein in the 140-kd region, which reacte d with a monoclonal antibody generated to the adhesin-implicated 140-k d protein (P140) of wild-type M. genitalium. Class II variants complet ely lacked the 140-kd protein or immunologically related peptides.