ADAPTIVE-CHANGES IN MEMBRANE-LIPIDS OF BAROPHILIC BACTERIA IN RESPONSE TO CHANGES IN GROWTH PRESSURE

The lipid compositions of barophilic bacterial strains which contained docosahexaenoic acid (DHA [22:6n-3]) were examined, and the adaptive changes of these compositions were analyzed in response to growth pres sure, In the facultatively barophilic strain 16C1, phosphatidylethanol amine (PE) and phosphatidylglycerol (PG) were major components which h ad the same fatty acid chains, However, in PE, monounsaturated fatty a cids such as hexadecenoic acid were major components, and DHA accounte d for only 3.7% of the total fatty acids, while in PG, DEW accounted f or 29.6% of the total fatty acids. In response to an increase in growt h pressure in strain 16C1, the amounts of saturated fatty acids in PE were reduced, and these decreases were mainly balanced by an increase in unsaturated fatty acids, including DHA. In PG, the decrease in satu rated fatty acids was mainly balanced by an increase in DHA, Similar a daptive changes in fatty acid composition were observed in response to growth pressure in obligately barophilic strain 2D2. Furthermore, the se adaptive changes in response were also observed in response to low temperature in strain 16C1, These results confirm that the general shi ft from saturated to unsaturated fatty acids including DHA is one of t he adaptive changes in response to increases in pressure and suggest t hat DHA may play a role in maintaining the proper fluidity of membrane lipids under high pressure.