ALTERATION OF FATTY-ACID COMPOSITION IN A PGSA3 MUTANT OF ESCHERICHIA-COLI

We examined the fatty acid composition in an Escherichia coli pgsA3 mu tant lacking the potential to synthesize phosphatidylglycerolphosphate , a precursor of phosphatidylglycerol. The contents of C18:1cis-9 (ole ic acid) and C18:1cis-11 (cis-vaccenic acid) in the total phospholipid s extracted from the pgsA3 mutant growing at 37 degrees C were higher and that of C14:0 was lower than the wild type cells, resulting in a h igher level of unsaturation of fatty acids (ratio of unsaturated fatty acids to saturated ones) in the mutant, The higher level of the unsat urated fatty acids in the pgsA3 mutant was more obvious in cardiolipin than in phosphatidylethanolamine. On the other hand, at 28 degrees C, at which the pgsA3 mutant shows limited cell growth, the content of u nsaturated fatty acids in cardiolipin decreased in the pgsA3 mutant co mpared with the wild type, We consider that the pgsA3 mutant maintains cellular homeostasis by altering the level of unsaturated fatty acids in cardiolipin, and the mechanism is influenced by temperature.