Mechanisms of nonpermissiveness in abortive infection of bacteriophage .PHI.NR2 in Bacillus subtilis Marburg strain.

Abstract

A mutant strain PS9, permissive to infection of phages SP1O and ¢NR2, was derived from a nonpermissive Marburg strain of Bacillus subtilis. When treated with mitomycin C or ultraviolet irradiation, PS9 cells lysed to produce defective phage PBSX as did the nonpermissive cells. Thus it was suggested that the nonpermissiveness might be independent of the repression system of the defective phage PBSX. As another approach to elucidate the mechanism of nonpermissiveness, DNA and RNA syntheses were analyzed in both permissive and nonpermissive cells infected with phage c N R2. By molecular hybridization with phage DNA, it was found that, in the nonpermissive cells, cNR2 DNA did not replicate but phage-directed RNA was partially synthesized.The RNA synthesized in the nonpermissive B. subtilis Marburg appeared to lack late messenger RNA compared to RNA synthesized in the permissive cells.Cells of Bacillus subtilis Marburg strain can adsorb phage SP1O but are nonpermissive to the replication of this phage and thus the Marburg strains can not serve as gene donors in generalized transduction by phage SP1O (1).GWINN and LAWTON (2) and GoLDBERG and BRYAN (3) reported that the cells of Marburg strain were rendered permissive to infection with phage SP1O by heating or mitomycin C treatment, and suggested that repressors of endogenous defective prophage PBSX may play a role in the nonpermissiveness of the B. subtilis Marburg strain.We have isolated a mutant of B, subtilis Marburg strain which is permissive to phage SP1O as well as a newly isolated phage NR2 (4) and attempted to study mechanisms of the nonpermissiveness in two respects. The first relates to the induction of PBSX in the permissive mutant, and the second is concerned with phage-directed DNA or RNA synthesis in nonpermissive and permissive hosts. In these studies we have used the ONR2 which is similar to phage SP1O with respect to the host specificity concerning the nonpermissiveness (5), since SP1O 291

Molecular Organization of Intrinsic Restriction and Modification Genes Bsu M of Bacillus subtilis Marburg

“…The hsrM1 and nonB mutations (24,36) which made host cells permissive to phage infection were isolated and mapped at around 50°on the B. subtilis chromosome (24), and it was thought that these mutations were mutations of the endonuclease gene of BsuM. On the other hand, strain RM125 (34) was constructed by transformation of wild-type B. subtilis Marburg 168 (YS11) with DNA from the related strain B. subtilis 202-5 (ϭ IAM1169, a B. amyloliquefaciens strain), which lacked restriction activity against phage 105.…”