Relationship between lysogeny, spontaneous induction, and transformation efficiencies in Bacillus subtilis.

The low transformation efficiency of Bacillus subtilis 168 lysogenic for phages ø105 or SPO2 is shown to result from the induction of lytic phage replication in competent cells. Lysogenic competent cells have a higher rate of spontaneous prophage induction than noncompetent cells. Mutants of ø105 and SPO2 which form lysogens resistant to spontaneous induction were isolated, and these lysogens exhibited higher transformation levels than those formed by wild-type phage. These results suggest that the physiological state of competence in B. subtilis promotes prophage derepression leading to cell death and the loss of potential transformants.