A recA-dependent mutator of Escherichia coli K12: Method of isolation and initial characterization

Abstract A number of mutator strains of E. coli were isolated using histochemical techniques which allow the identification of a single mutator colony on agar plates with as many as 2000 colonies. Several mutators isolated in this way were found by P1-mediated transduction to map to the proA-proB region of the E. coli chromosome. The map position of these mutators is very close to that of the conditional mutator, mutD . However, in contrast to mutD , one of these newly isolated mutators was suppressed in thermosensitive recA strain at 43°C, but not at 30°C. This mutator mutation has been named mut-8 . Besides being dependent upon recA, mut-8 is also dependent upon growth in enriched medium for the expression of its mutator activity. The mutator activity of mut-8 was found to be recessive to the wild-type allele.