Saturated fatty acids as bacterial antimetabolites

Abstract

Inhibitory effects of saturated fatty acids of from 7 to 24 carbons in length on nine species of lactic acid bacteria have been investigated. The inhibitions due to the acids of from approximately 12 to 20 carbons in length (depending on the test organism) have been shown to be the result of a potent antimetabolite effect, readily reversible by any of the six unsaturated fatty acids (oleic, linoleic, ricinoleic, vaccenic, licanic, and erucic acids) and the one cyclopropane acid (lactobacillic acid) tested. The inhibitions due to saturated fatty acids of longer chain length (22 and 24 carbons) nearly equal those of the most active saturated acids in the 12- to 20-carbon range, but the mechanism of these inhibitions has not been investigated. The short-chain fatty acids (12 and fewer carbons) are relatively feeble inhibitors and appear to act primarily according to the physicochemical hypotheses which have been proposed by earlier investigators. A scheme of metabolic pathways suggested by the present findings and correlating the latter with earlier data concerning bacterial lipide metabolism is proposed.