Fatty acid metabolism in Serratia marcescens: IV. The effect of temperature on fatty acid composition

An analysis of the fatty acids of Serratia marcescens grown at different temperatures shows that three medium-chain hydroxy acids, present in cells grown at 30°, are greatly decreased in quantity when the cells are grown at 37°. The content of unsaturated and cyclopropane acids remains unchanged. As the synthesis of unsaturated and cyclopropane acids in micro-organisms requires hydroxy acids as intermediates, it is suggested that the temperature-sensitive reaction is a reaction leading to the trapping of the hydroxy acids in a bound form. An analysis of the cellular fatty acids of a nonpigmenting strain of S. marcescens has revealed the presence of 12 unidentified acids. These acids, which constitute 36% of the total fatty acids of the “free” lipid of cells grown at 30° are almost entirely absent in cells grown at 37°.