TEMPERATURE-INDUCED CHANGES IN THE FATTY-ACID COMPOSITION OF THE CYANOBACTERIUM, SYNECHOCYSTIS PCC6803

Changes in glycerolipid and fatty acid composition with a change in growth temperature were studied in the cyanobacterium, Synechocystis PCC6803. Under isothermal growth conditions, temperature did not significantly affect the composition of the various classes of lipids, but a decrease in temperature altered the degree of unsaturation of C18 acids at the sn-1 position, but not that of C16 acids at the sn-2 position of the glycerol moiety in each class of lipids. When the growth temperature was shifted from 38°C to 22°C, the desaturation of C18 acids, but not that of C16 acids, was stimulated. The desaturation of fatty acids occurred only in the light and was inhibited by chloramphenicol, rifampicin and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, but not by cerulenin, an inhibitor for fatty acid synthesis. These findings suggest that desaturase activities are induced after a shift from a higher to a lower temperature, and that the desaturation of fatty acids is connected with the reactions involved in photosynthetic electron transport.