Synechocystis PCC6803 Mutants Defective in Desaturation of Fatty Acids

Two mutants, which were defective in desaturation of fatty acids, were isolated from the cyanobacterium, Synechocystis PCC6803, by treating wild-type cells with ethyl methanesulfo-nate. They were designated as Fad6 and Fadl2. Fad6 was defective in desaturation at the δ6 position of C18 fatty acids esterified to the sn -l position of glycerol moiety in monogalactosyl diacylglycerol and digalactosyl diacylglycerol but not sulfoquinovosyl diacylglycerol and phos-phatidylglycerol. This observation suggests that the desaturation affected in this mutant was specific to the sn-glycerol position, the chain length and the polar head group. Fadl2 was defective in desaturation at the δ12 position of C18 fatty acids at the sn -l position of glycerol moiety in all the lipid classes. This observation suggests that the desaturation affected in this mutant was specific with respect to the sn-glycerol position and the chain length of fatty acids, but not to the polar head group of the lipids. At 22°C Fad6 grew as fast as the wild type, but the growth rate of Fadl2 was much lower than that of wild type. At 34°C, on the other hand, the mutants and wild type grew at about the same rates.