Isolation and properties of Bacillus subtilis strains lysogenized by a clear plaque mutant of bacteriophage phi 105.

A clear plaque mutant of the temperate Bacillus phage phi105 lysogenized a small fraction of infected cells forming an integrated prophage at or near the normal phi105 insertion site. These lysogens exhibited a spontaneous induction rate approximately 1,000-fold lower than wild type and were noninducible (ind(-)) by mitomycin C. Prophage was induced, however, when competent cultures were incubated with transforming DNA. The ind(-) phenotype could not be attributed solely to the clear plaque mutation and appears to involve a cell-specific factor. Lysogenization by the clear plaque mutant, in contrast to wild-type phage, did not cause a marked reduction in transformation efficiency.