ALTERATION IN LEVELS OF UNSATURATED FATTY-ACIDS IN MUTANTS OF ESCHERICHIA-COLI DEFECTIVE IN DNA-REPLICATION

We previously reported that mutations in the dnaA gene which encodes t he initiator of chromosomal DNA replication in Escherichia coli caused an alteration in the levels of unsaturated fatty acids of phospholipi ds in membranes. In this study, we examined fatty acid compositions in other mutants which are defective in DNA replication, As in the case of temperature-sensitive dnaA mutants, temperature-sensitive dnaC and dnaE mutants, which have defects in initiation and elongation, respect ively, of DNA replication she-wed a lower level of unsaturation of fat ty acids (ratio of unsaturated to saturated fatty acids) compared with the wild-type strain, especially at high temperatures, On the other h and, temperature-sensitive mutants defective in cellular processes oth er than DNA replication, such as RNA synthesis and cell division, did not show a lower level of unsaturation of fatty acids compared with th e wild-type strain, These results suggest that the inhibition of DNA r eplication causes a lower level of unsaturation of fatty acids in Esch erichia coli cells.