Fine structure genetic map and complementation analysis of mutations in the dnaA gene of Escherichia coli

A fine structure genetic map of several mutations in the dnaA gene of Escherichia coli was constructed by the use of recombinant lambda and M13 phages. The dnaA508 mutation was found to be the mutation most proximal to the promoter, while the dnaA203 mutation was found to be the most distal one. The order of mutations established in this analysis was: dnaA508, dnaA167, (dnaA5, dnaA46, dnaA211), dnaA205, dnaA204, dnaA203. The mutations dnaA601, dnaA602, dnaA603, dnaA604 and dnaA606 were found to map very close to each other and close to dnaA205 in the middle third of the dnaA gene. In analysing the dominance relationship all 13 dnaA mutations were found to be recessive to the wild type. Characteristic phenotypes of the dnaA(Ts) mutants, like reversibility of the temperature inactivation of the dnaA protein, cold sensitivity of haploid or of merodiploid strains and suppressibility by rpoB mutations, are found to correlate with clusters of mutations within the gene.