INFLUENCE OF TEMPERATURE ON FATTY ACID COMPOSITION OF PSYCHROPHILIC AND MESOPHILIC SERRATIA SPECIES.

Abstract

Growth of Serratia marcescens at 10° resulted in a decrease in the amounts of cyclopropane and palmitic acids, relative to those at 30°, and corresponding increases in monoenoic (hexadecenoic and octadecenoic) acids. A Serratia-like psychrophile grown at 5° or 10° had large proportions of monoenoic acids (chiefly hexadecenoic acid but not octadecenoic acid) but no cyclopropane acids. When grown in media containing L-methionine or S-adenosyl methionine (known cofactors for biosynthesis of the cyclopropane ring), the psychrophile still did not produce any cyclopropane acids. The phosphatide composition of the psychrophile was similar to that of S. marcescens with respect to the presence of phosphatidyl ethanolamine, phosphatidyl glycerol, and other acidic phosphatides, but the lipo-amino acids found in S. marcescens were not detected in the psychrophile.The present data support the classification of the psychrophile as a species of Serratia, but suggest that it has lost the ability to synthesize cyclopropane acids, perhaps as a result of adaptation to growth at low temperatures.