FATS AS ESSENTIAL DIETARY COMPONENTS 895 



possess an inhibitory effect upon the growth of various Gram-positive organ- 

 isms. This behavior apphes both to the long-chain saturated and to the 

 unsaturated acids aHke. Laurie and mj'ristic acids inhibit bacterial growth 

 in concentrations as small as 1 :100,000. In the case of unsaturated acids, 

 the CIS forms exhibit a marked retarding effect on growth, and an increased 

 effect is noted in the case of the polyunsaturated acids. Thus, the toxicity 

 occurs in the follo\\'ing order: oleic acid < linoleic acid < linolenic acid. 

 The bacteriostatic action of the unsaturated acids can be reversed by 

 surface-active agents such as lecithin, sterols, tocopherols, proteins, and 

 similar compounds. On the other hand, esters of the fatty acids are not 

 bacteriostatic. In contradistinction to the reversal of the inhibitory 

 effect of the surface-active agents upon the unsaturated acids, these agents 

 were ineffective in the case of the long-chain saturated acids. 



Laser-"'^^^ found that m-vaccenic acid inhibited respiration and growth 

 of Bacillus suhtilis. The respiratory inhibition decreased with time, and 

 was followed by an increase in oxidation rate. This phenomenon is ex- 

 plained on the basis of a penetration of the acid into the cell w^hich results 

 in an unspecific inhibition of the succinic oxidase system within the cell. 

 The organism is gradually able to metabohze the penetrated acid, and the 

 metabolism returns to normal. Tmns-vaccenic acid was found to have 

 only about half of the activity of the as acid.-" In later studies by 

 Laser, -^^' 260 it was found that the respiration of B. siibtilis was inhibited 

 quahtatively in a similar manner but quantitatively to different degrees 

 by stearic, oleic, vaccenic, and oleic acid. However, after a certain length 

 of time, resistance develops in the growing cells ; this is believed to be the 

 result of the production of an adaptive enzyme. Tomarelli et al.-^^ found 

 that long-chain fatty acids have a bacteriostatic effect upon Lactobacillus 

 bifidus. Laurie and m3'ristic acids were found to be the most toxic, but 

 sodium acetate, oleic, and linoleic acid were also markedly inhibitory to 

 the bifid strain. The presence of factors which alleviate the toxicity of the 

 fatty acids was demonstrated in both human and cow's milk. These 

 factors were found in bovine serum albumin, in dialyzed human whey, 

 and in acacia suspension. A similar reversal of fatty acid toxicity was 

 afforded by surface-active compounds such as Tween 80, Tween 60, and 

 lipositol. Broquist and SnelP'^- demonstrated that the oleic acid "in- 



^^ H. Laser, Biochem. J., 47, xxxii-xxxiii (1950). 

 2M H. Laser, Biochevi. J., 48, 164-170 (1951). 

 ^3 H. Laser, Biochem. J., 49, Ixvi-lxvii (1951). 

 2«o H. Laser, Biochem. J., 51, 57-62 (1952). 



2" R. M. Tomarelli, R. F. Norris, C. S. Rose, and P. Gyorgy, /. Biol. Chem., 187, 197- 

 204(1950). 



»« H. P. Broquist. and E. E. Snell, /. Biol. Chem., 173, 435-436 (1948). 



