Fatty acid compositions of lipid fractions from vegetative cells and mature sorocarps of the cellular slime mold Dictyostelium discoideum.

A wild-type strain of Dictyostelium discoideum was grown upon Aerobacter aerogenes. Fatty acid compositions of lipid fractions and of total lipids obtained from vegetative amoebae and mature sorocarps were compared. Fatty acids isolated from vegetative cells were found to include large quantities of 17- and 19-carbon cyclopropane fatty acids while straight-chain, saturated fatty acids represented only 10% (w/w) of total fatty acids. These cyclopropane fatty acids appear to be derived from ingested bacteria and are preferentially incorporated into neutral lipids of the slime mold. Development of amoebae to mature sorocarps is accompanied by a substantial decrease in cyclopropane fatty acid content and a concomitant increase in unsaturated fatty acids, mostly as octadeca-5,11-dienoic acid. The delta-22 stigmastenyl ester fraction is the richest source of this acid. Fully 65% of the fatty acids in this fraction are the octadecadienoate.