Fatty acid composition of the cellular slime mold Polysphondylium pallidum.

The cellular slime mold Polysphondylium pallidum was grown upon Escherichia coli B/r, and the fatty acid compositions of total lipids obtained from vegetative amebae and aggregation-competent cells were compared. Fatty acids isolated from vegetative cells included C-17 and C-19 cyclopropane fatty acids and also straight-chain, saturated fatty acids. The cyclopropane fatty acids were derived from the ingested bacteria. Development of amebae to aggregation-competent cells was accompanied by a substantial decrease in saturated cyclopropane fatty acids and a concomitant increase in unsaturated fatty acids and unsaturated cyclopropane fatty acids, mostly as 18:3 (5,9,12). We report here the fatty acid composition and identify the occurrence of delta 5 desaturation of cyclopropane fatty acids, namely, 9,10-methylene 5-hexadecenoic acid and 11,12-methylene 5-octadecenoic acid. These fatty acids have not been reported previously in the related species Dictyostelium discoideum, which also feeds on E. coli B/r and has delta 5-desaturation activity.