Action of inhibitors of macromolecule formation on duplication of B. subtilis phage 2C-DNA

Abstract

The action exerted by inhibitors of DNA, RNA and protein synthesis on the replication of B. subtilis phage 2C and on the duplication of its DNA was investigated. Virus yield was reduced by all the antibiotics tested, the most active drugs being actinomycin, rifampicin and the mixture of the two virginiamycin components VM and VS. The effect of these inhibitors on virion formation was irreversible, whereas that of chloramphenicol, nalidixic acid, mitomycin and of VM and VS separately was fully reversible. The phage genome, containing hydroxymethyluracil instead of thymine, was labeled by adding [ 3H]uracil to infected cells. Hence, this precursor was used to monitor the action of inhibitors on viral DNA replication. Actinomycin prevented completely viral DNA formation at any moment of the viral cycle, whereas the effect of rifampicin was restricted to the eclipse phase. Duplicational and translational inhibitors (mitomycin, nalidixic acid, chloramphenicol, VM and VS), were partly inhibitory during the entire replication cycle, the extent of inhibition of DNA synthesis being inversely related to the time elapsed from infection. The implication of these findings on the pattern of macromolecule formation during the viral cycle is discussed.