Induction of polyunsaturated fatty-acid synthesis enhances tolerance of a cyanobacterium, Cylindrospermopsis raciborskii, to low-temperature photoinhibition

Acyl-lipid desaturation introduces double bonds (unsaturated bonds) at spec ifically defined positions of fatty acids that are esterified to the glycer ol backbone of membrane glycerolipids. Desaturation pattern of the glycerol ipids of Cylindrospermopsis raciborskii (C. raciborskii), a filamentous cya nobacterial strain, was determined in cells grown at 35 degreesC and 25 deg reesC. The lowering of the growth temperature from 35 degreesC to 25 degree sC resulted in a considerable accumulation of polyunsaturated octadecanoic fatty acids in all lipid classes. Lipid unsaturation of C. raciborskii was also compared to Synechocystis PCC6803. In C. raciborskii cells, a shift in growth temperature induced a much more pronounced alteration in the desatu ration pattern of all lipid classes than in Synechocystis PCC6803. The tole rance to low-temperature photoinhibition of the C. raciborskii cells grown at 25 degreesC and 35 degreesC was also compared to the tolerance of Synech ocystis cells grown at the same temperatures. Lower growth temperature incr eased the tolerance of C. raciborskii cells but not that of Synechocystis c ells. These results strengthen the importance of polyunsaturated glycerolip ids in the tolerance to environmental stresses and may give a physiological explanation for the determinative role of C. raciborskii strain in algal b looming in the Lake Balaton (Hungary).