Replacement of the Aliphatic Chains of Clostridium acetobutylicum by Exogenous Fatty Acids: Regulation of Phospholipid and Glycolipid Composition

The membrane lipid aliphatic chains of Clostridium acetobutylicum ATCC 4259 have been extensively modified by growth in biotin-free medium containing vitamin-free casein hydrolysate supplemented with either elaidic acid, oleic acid, or mixtures of palmitic and oleic acids. Growth with elaidic acid resulted in polar lipids containing 88.6 % 18:1 acyl chains and 94.5 % 18:1 ether-linked chains. Growth with oleic acid resulted in comparable levels of enrichment of the lipids with 18:1 chains and Cl9 chains containing cyclopropane rings. When cells were grown with mixtures of palmitic and oleic acids, the ether-linked chains of the plasmalogens were>64%o 18:1 plus C19 chains containing cyclopropane rings at all ratios of oleic to palmitic acid in the medium. The acyl chains reflected the palmitic acid content of the medium more closely. Marked changes were observed in both phospholipid and glycosyldiglyceride compositions as the lipid acyl and ether-linked chains became more enriched with unsaturated and cyclopropane chains. The ratio of the glycerol acetal of plasmenylethanolamine to phosphatidylethanolamine increased, the ratio of cardiolipin to phosphatidylglycerol decreased, and the ratio of diglycosyldiglyceride to monoglycosyldiglyceride increased. However, the mono-glycosyldiglyceride/diglycosyldiglyceride ratio was lower for cells grown on 100%o oleic acid than for cells grown on 60 or 80 % oleic acid. In the membranes of cells grown on 100 % oleic acid, the ratio of glycolipids to phospholipids was lower than that found in cells grown on 60 % oleic acid. These results indicate that C