Characterization of recombination-deficient mutants of Bacillus subtilis

An isogenic set of "prophage-free," DNA repair-proficient and -deficient strains of Bacillus subtilis were characterized phenotypically. The mutant strains were provisionally classified into four categories on the basis of their sensitivity to DNA-damaging agents, their ability to release phage after lysogenization followed by damage to chromosomal DNA, and their impairment in genetic exchange. The properties of double Rec- mutants showed that recF and addA belong to different epistatic groups, whereas recF, recL, and recH fall into the same group. More than one pathway for genetic exchange might be operative in B. subtilis.