Induction of the Bacillus subtilis SOS-like response by Escherichia coli RecA protein.

A plasmid that expresses the Escherichia coli RecA protein partially restored DNA repair and recombination capability and induction of the SOS-like (SOB) response in a recE4 mutant of Bacillus subtilis. In the presence of DNA-damaging agents, the E. coli RecA protein induced din operon expression, Weigle-reactivation activity, and synthesis of a B. subtilis recombination protein (Recbs) analogous to RecA but was unable to stimulate prophage induction. In addition, the RecA protein was capable of inducing the SOB response in competent recE4 strains of B. subtilis, independent of exposure to DNA-damaging agents. The results suggest that (i) the SOS response of E. coli and the SOB response of B. subtilis are strikingly similar from both a phenotypic and a regulatory standpoint and that RecA and LexA protein analogs exist in B. subtilis, (ii) the Recbs protein is capable of regulating its own production, and (iii) SOS-inducing (RecA-activating) signals are generated in B. subtilis following either DNA damage or the development of physiological competence.