INTERACTION OF PROPIONIBACTERIUM-ACNES WITH SKIN LIPIDS IN-VITRO

Propionibacterium acnes in the predominant microbial resident within t he pilosebaceous follicles of sebum-rich areas of human skin. This stu dy investigated the effects of known hydrophobic components of sebum o n the physiology and nutrition of this microorganism, grown anaerobica lly at 3.3-degrees-C, under defined conditions using continuous cultur e techniques. The medium used was chemically defined, comprising eight amino acids, with glucose as the main carbon energy source and the cu lture pH was maintained at 5.6. The range of sebum lipids assayed was based on the C18 monounsaturated fatty acid 9-cis-octadecenoic acid (o leic acid). Stock micronized solutions were aseptically pulsed into co ntinuous cultures in the presence and absence of glucose, and nutritio nal effects monitored. None of the lipid substrates significantly affe cted P. acnes growth either in terms of maximum specific growth rate ( mu(max)) or final culture biomass yield. Glycerol (3 mg ml-1) was foun d to be a poor carbon/energy source in comparison to glucose. Bacteria l cells did, however, adhere with varying degrees, to the different li pid species, with maximum adherence occurring with the free fatty acid . This observation was confirmed by preliminary uptake experiments usi ng [C-14]oleic acid. The interactive site for cell adherence may be th e lipid-fibrillar layer associated with the cell surface of P. acnes, as discerned in electron microscopical studies. The findings of this i nvestigation suggest that one function of the P. acnes lipase may be t o aid colonization within the pilosebaceous follicle, by promoting cel l adherence to components such as oleic acid.