Characteristic presence of polyunsaturated fatty acids in marine psychrophilic vibrios

The cellular fatty acid compositions of 22 psychrophilic and psychrotrophic vibrios isolated from deep-sea sediment samples were analyzed. Twelve isolates were shown to contain docosahexaenoic acid (22:6), and five isolates contained eicosapentaenoic acid (20:5). The presence of these polyunsaturated fatty acids and the maximum growth temperatures of the isolates were correlated. Those containing docosahexaenoic acid possessed the lowest maximum growth temperatures (lower than 20° C, Group I), while those containing eicosapentaenoic acid had maximum growth temperatures between 20 and 25° C (Group II). A group of five isolates which did not contain such polyunsaturated fatty acids had higher maximum growth temperatures (Group III). These results imply that those polyunsaturated fatty acids may play a role in low-temperature adaptation of marine vibrios and suggest that the presence of polyunsaturated fatty acids could be used to discriminate between psychrophilic and psychrotolerant marine bacteria.