Genetic control of bacterial suicide: regulation of the induction of PBSX in Bacillus subtilis.

PBSX is a phage-like bacteriocin (phibacin) of Bacillus subtilis 168. Bacteria carrying the PBSX genome are induced by DNA-damaging agents to lyse and produce PBSX particles. The particles cannot propagate the PBSX genome. The particles produced by this suicidal response kill strains nonlysogenic for PBSX. A 5.2-kb region which controls the induction of PBSX has been sequenced. The genes identified include the previously identified repressor gene xre and a positive control factor gene, pcf. Pcf is similar to known sigma factors and acts at the late promoter PL, which has been located distal to pcf. The first two genes expressed from the late promoter show homology to genes encoding the subunits of phage terminases.