Influence of trace amounts of fatty acids on the growth of microorganisms.

A better understanding of the inhibitory and and linolenic acids on pneumococci at a concenstimulating effects of fatty acids on the growth of tration of 40 ppm, whereas 200 ppm exerted a microorgankisms may contribute to a clearer bactericidal influence. Streptococci were someappreciation of some general nutritional probwhat more resistant; according to Walker (82) lems, such as: they were inhibited by 100 ppm fatty acid soaps. a. Can dietary fat fulfill a nutritional function Antibacterial properties of some fatty acids in higher organisms other than as a source of were demonstrated later with pure cultures of calories or as a carrier of fat-soluble vitamins gram positive cocci belonging to the Micro(including the essential unsaturated fatty acids)? coccaceae (micrococci and staphylococci) and b. Can the resistance of higher organisms Lactobacteriaceae (pneumococci and streptoagainst infectious diseases be related to the incocci). Kodicek and Worden (49) succeeded in take of fat with the diet? inhibiting growth of Streptococcus agalactiae and c. Can the effect of fatty acids on unicellular Staphylococcus albUs with 16-32 ppm linoleic organisms be related to the fatty acid metaboacid. Humfeld (44) discussed the inhibition of lism in the tissues of higher organisms? Streptococcus lactis (S. faecalis, R), Staphylococcus The following survey deals chiefly with various aureus and Micrococcus conglomeratus by some aspects of the role of fatty acids as antibacterial tenthsppm oleate orlinoleate. Witha Micrococcus and growth promoting agents; the bibliography species ("C") Dubos (20) observed an inhibitory stresses recent contributions to these aspects. influence of as little as 0.1-1 ppm oleic acid. McKee et al. (59) described the antibacterial I. FATTYS ACIDS AM ANIAEIA AGENTS effect of approximately 15 ppm oleic acid on Most of the earlier observations concerning pneumococci, streptococci and staphylococci. the inhibitory properties of fatty acids on micro2. Lactobacili. More recently the antibacterial bial growth stem from studies on soaps, in relaeffect of fatty acids on LactobaciUus species has tively high concentrations, as antiseptics and been investigated. This is of particular interest disinfectants. However, this review is limited to because with several homofermentative lactic antibacterial activities in vitro of very low conacid producers growth promoting properties of centrations of fatty acids. As a rule only the fatty acids were also observed. effects of concentrations within the range of According to Strong and Carpenter (78) solubility of the higher fatty acids (5-50 ppm) LactobaciUus helveticus (L. casei e) showed growth will be mentioned. For these concentrations it inhibition by both linoleic and palmitic acid. is irrelevant whether the fatty acids are present This was confirmed by Bauernfeind et al. (6) for in the free form or as alkali soaps. All concentralinoleic acid (16 ppm). Also the fatty acid mixtions have been converted to ppm. ture from butterfat proved to be inhibitory for 1. Gram positive cocci. Gram positive cocci growth of this organism, as shown by Boutwell provided the first data on the antibacterial action et al. (8). of minute amounts of fatty acids. Lama (53) Other fatty acids inhibitory for L. helveticus mentioned the inhibitory effect of oleic, linoleic are oleic and linolenic acids in a concentration of