Induction of HFR formation in F[raised +] males of Escherichia coli treated with MNNG

N-methyl-N'-nitro-N-nitrosoguanidine, MNNG, was shown to stimulate the formation of Hfr males in a F[raised +] population of Escherichia coli. The frequency of Hfrs is raised 23.3 fold, with MNNG treatment, above that of spontaneous Hfr formation. At least twelve different sites of F factor integration were found in MNNG induced Hfrs. Several possible mechanisms of the MNNG induced F factor integration process were studied. A model for Hfr formation has been discussed.