The Effect of Bacteriophage λ on Host Cell Reactivation in Escherichia coli K12

SUMMARY: Host cell reactivation (hcr) of phage T1 by two strains of Escherichia coli K12, Hfr C (λ+) thy − and Hfr B1 (λ−) thy −, was studied. Strain HfrC showed decreased ability to reactivate ultraviolet (u.v.)-irradiated phage T1, as predicted from its behaviour in mating experiments after thymine starvation. Thymine starvation of host Hfr B1 bacteria resembled u.v. irradiation in decreasing hcr, but thymine starvation of Hfr C increased hcr, apparently as a result of λ induction. The presence of λ prophage in E. coli K12 was found to decrease hcr.