Effect of growth temperature on the fatty acid composition of Mycobacterium phlei

In Mycobacterium phlei, fatty acid unsaturation increased with decreasing temperature. The 10-hexadecenoic acid content increased as the temperature was reduced from 35°C to 26–20°C. At lower temperatures tuberculostearic acid decreased while oleic and linoleic acids increased, the latter being found in M. phlei for the first time. Concomitantly palmitic acid content decreased, and the 6- and 9-hexadecenoic acids increased slightly on reducing the temperature from 35 to 10°C. Thus, down to 26–20°C palmitic acid was mainly replaced by 10-hexadecenoic acid. From this range down to 10°C, palmitic and tuberculostearic acids were replaced by oleic and linoleic acids. Consequently, fatty acid branching decreased and mean chain length increased, as the temperature was reduced. These observations support the view that regulation of membrane fatty acid composition is part of microbial temperature adaptation, and that themechanism behind the responses might be more complex than generally believed.Abbreviations ACP acyl carrier protein - FAS I (Type I) fatty acid synthetase I - FAS II (Type II) fatty acid synthetase II - MGLP methylglucose containing lipopolysaccharide - MMP methylmannose containning polysaccharide