The role of temperate bacteriophage SPβ in prophage-mediated interference in Bacillus subtilis

Abstract

Virulent bacteriophage [Formula: see text] grows on a variety of Bacillus subtilis strains. Mutants of this virus which abortively infect the transformable bacillus, B. subtilis 168, while retaining the ability to productively infect related bacteria have been found. In the present study, we demonstrate that the inability of one such variant, [Formula: see text], to develop normally in strain 168 is mediated by cryptic prophage SPβ. The latter is a temperate bacteriophage which is carried by B. subtilis 168 and most strains derived from this bacterium. [Formula: see text] infection of SPβ lysogens begins with apparently normal adsorption, penetration, and initiation of virus-directed syntheses. At about the 20th min of the latent period, however, there is an abrupt cessation of nucleic acid synthesis and cellular respiration, accompanied by a change in cell permeability. This course of events can be altered to a permissive infection by mutation in the mpi gene of SPβ, by mutation in the spo0A gene of the host, or by growing SPβ lysogens at high temperature. In addition, we found a second class of [Formula: see text] mutants which abortively infect B. subtilis 168 derivatives even in the absence of the SPβ prophage.