W-reactivation and W-mutagenesis of gamma-irradiated phage lambda.

UV irradiation of Escherichia coli wild-type cells manifested the phenomena of W-reactivation (WR) and W-mutagenesis (WM) of phage lambda irradiated by 60Co gamma-rays in broth. WR of gamma-irradiated phage was half as efficient as that of UV-irradiated phage, although the frequency of c mutations in conditions of WR was about the same in both phages. The xthA and recBrecC sbcB mutants were practically identical with wild-type cells in respect of WR and WM of UV- and gamma-irradiated phage. As in UV-irradiated phage, WR and WM of gamma-irradiated phage were absolutely dependent on the recA+ and lexA+ genes of the host cell. WR and WM required much smaller doses of UV radiation for induction in polA1 and uvrB mutants. The lig-ts mutant, temperature sensitive in polynucleotide ligase, was deficient in WR and WM of UV- and gamma-irradiated phage at the semi-permissive temperature of 37 degrees. The uvrE502 mutant and the allelic recL152 strain were absolutely deficient in WR and WM of gamma-irradiated phage. In UV-irradiated phage WR was reduced, but not eliminated, in the uvrE mutant, and WM was entirely suppressed. This is another example of uncoupling of WR and WM which shows that several repair systems are active in WR but only some of them are mutagenic.