TRANSFORMATION OF STEROLS BY MYCOBACTERIUM-VACCAE - EFFECT OF LECITHIN ON THE PERMEABILITY OF CELL ENVELOPES TO STEROLS

An enhancement of beta-sitosterol transformation to androstendione by Mycobacterium vaccae observed in medium containing egg-yolk lecithin, was associated with the incorporation of a considerable amount of leci thin into the cell envelope lipids, By GC/MS measurements, fatty acids ranging from 14 to 22 carbon atoms were identified in the lipids remo ved from the cells by organic solvents. Octadecenoic (18:1), 2-methyl- octadecenoic (2-Me 18:1), and hexadecanoic (16:0) acids were the major components of the lipid preparation obtained from both the control ce lls, and the cells grown in lecithin-containing medium. However, in th e fatty acid pattern of the latter a distinct increase in the C-18:1 c omponent, concomitant with the decrease in the 2-Me 18:1 fatty acid wa s demonstrated. The C-16 fatty acid fraction also showed a higher cont ent of methyl-branched components in the control cell preparation, The enrichment in unsaturated fatty acids increases fluidity of lipids, w hereas the decrease in methyl-branched fatty acids may affect the conf ormation of the surface lipidic components, which may result in enhanc ed sterol penetration through the cell wall barrier in the presence of lecithin.