Bacteriophage conversion of spore-negative mutants to spore-positive in Bacillus pumilus

Abstract

A pseudolysogenic phage, PMB1, was isolated from soil on the basis of its ability to increase the sporulation frequency of the oligosporogenic Bacillus pumilus strain NRS 576 (sporulation frequency, <1%). Several spore-negative mutants (sporulation frequency, <10-8) derived from strain NRS 576, which were converted to spore positive by infection with PMB1, were subsequently identified. PMB1 repeatedly grown on a given spore-negative mutant (e.g., GW2) converted GW2 cells to spore positive. Each plaque-forming unit initiated the conversion of a spore-positive clone in semisolid agar overlays. GW2 cells remained spore positive as long as they maintained PMB1. Return of PMB1converted cells to the original spore-negative phenotype correlated with loss of PMB1. In liquid media, PMB1 infection increased the sporulation frequency of mutant GW2 over 106-fold. More than half of the spore-negative mutants we isolated from strain NRS 576 were converted to spore positive by PMB1 infection. PMB1-induced spores of the spore-negative mutant GW2 were somewhat more heat sensitive than uninfected or PMB1-infected spores of the sporepositive parent of GW2. PMB1-induced spores of GW2 do not differ from wildtype spores in morphology by phase-contrast microscopy, dipicolinic acid content, or rate of sedimentation through Renografin gradients.

Synthesis of deoxythymidylate and the unusual deoxynucleotide in mature DNA of Bacillus subtilis bacteriophage SP10 occurs by postreplicational modification of 5-hydroxymethyldeoxyuridylate

“…Bacteriophage 4OW-14 DNA contains equimolar quantities of dTMP and the deoxynucleotide of a-putrescinylthymine (16), both of which are derived by postreplicational modification of a common precursor that is probably HMdUMP (22, 26). PMB1 is a "spore converting" phage for Bacillus pumilis (6). Mature PMB1 DNA has the same nucleotide composition as SP10 DNA, but the DNAs show little sequence homology (H. Witmer, unpublished data).…”

Isolation of Nontoxigenic Variants Associated with Enhanced Sporulation and Alteration in the Cell Wall from Clostridium botulinum Type A 190L by Treatment with Detergents

“…The present work suggests that the existence of prophage may be closely related to the oligosporogenic phenotype of the parent strain of C. botulinum type A. However, Bramucci et al found that the one of the phages, PMB1, converted certain sporenegative mutants of B. pumilus to spore positive mutants (1), and the other phage, PMB12, complemented the sporulation defect in RNA polymerase mutants of Bacillus subtilis (2). Thus, the relationship between sporogenicity and the existence of plasmid or prophage has not yet been generally determined.…”

Lysogeny in Bacillus

“…A variation in the Oantigens of Salmonellae [ 16], the colony morphology in Streptococcus equi [17], toxin production in Co-rynebacterium diphtheriae [ 18,19 ], Clostridium botulinum [20] and Vibrio cholerae [21 ], phospholipase A production in B. cereus [22], thymidylate synthetase activity in a thymine deficient mutant of B. subtilis [23] and sporulation in spore-negative strains of8. pumilus [24] are all directed by prophages. As approximately half of the strains tested in this study were lysogenic, we considered whether this property had any survival value.…”