SYNTHESIS OF DNA IN PHAGE-INFECTED BACILLUS SUBTILIS

The hydroxymethyl-uracil-containing bacteriophage ∅e causes inhibition of host DNA synthesis in Bacillus subtilis 3610. This inhibition is not accompanied by breakdown of the host DNA to acid-soluble form nor by production of double-strand breaks in it. The inhibition of thymidylate synthetase produced by this phage is not responsible for the arrest of host DNA synthesis observed after 6 minutes of infection at 37° since the arrest is still observed in bacterial mutants requiring and actively using exogenous thymine. The role of the phage-induced deoxythymidine triphosphate nucleotidohydrolase (dTTPase) in producing the arrest of host DNA synthesis has been investigated using phage mutants which induce temperature-sensitive dTTPase. Even under conditions in which the dTTPase level is low enough to permit incorporation of some thymine into the DNA of the phage, there is still an inhibition of host-DNA synthesis at the usual time after infection. The results suggest, but do not prove, that the phage may give rise to some additional mechanism, besides the induction of dTTPase, resulting in inhibition of host DNA. It is not yet known whether the phage particles with thymine-containing DNA are normally functional. © 1969.