Suppression of an Escherichia coli dnaA mutation by the integrated R factor R100.1: origin of chromosome replication during exponential growth

Abstract

The behavior, during exponential growth, of strains of E. coli carrying a dnaA (Ts) mutation that was suppressed by the integration of the F-like R plasmid R100.1 was investigated. Replication in these strains proceeds largely from the normal chromosome origin at 30.degree. C, a permissive temperature for the dnaA (Ts) gene product, but at 42.degree. C, replication proceeds largely from the integrated plasmid. These conclusions are based on measurements made by DNA:RNA hybridization of the relative frequencies of the prophages Mu-1 and .lambda.ind- and R100.1 integrated at known locations on the E. coli chromosome in these Hfr strains.