[W-reactivation and W-mutagenesis in UV-irradiated phage phil05 of Bacillus subtilis]

The survival of UV-irradiated phage ø105 on the lawns of several strains of Bacillus subtilis: wild type (strain 168) and 11 recombination-defficient mutants (recA1, recB2, recB3, recB19, recD27, recF15, recF18, recK4, recM13, recL16 and recO61) was investigated. All rec mutants have the phenotype Hcr+, i.e. normally host-cell reactivate UV-damaged phage. Small doses of UV-irradiation given to the wild type (rec+) cells increase the probability of survival of UV-irradiated ø105 phage (W-reactivation) and significantly enhance the frequency of c-mutants (W-mutagenesis). Maximal frequency of clear mutations in conditions of W-mutagenesis is 3-10(-3), i.e. is 100 times higher than the spontaneous background. Various rec mutations of host cells only diminish the level of W-reactivation but do not eliminate it completely. The most deficient in W-reactivation is recD27 mutant. Mutations recB2, B3, B19 and O61 have no effect on W-mutagenesis of UV-irradiated phage ø105 and on UV-induction of ø105, F15,F18 and L16 mutants. UV-irradiation of lysogenic cells of these mutants does not induce ø105 prophage.