The effect of rifampicin on the development of the Streptomyces bacteriophage phi C31

The production of phi C31 progeny virus was inhibited by rifampicin when it was added at any time before 20 minutes after induction of the thermoinducible lysogen Streptomyces coelicolor 01. The inhibition was gradually lost as the antibiotic was being added later on until the end of the latent period, which lasts about 45 minutes. This effect was not due to resistance of transcription to rifampicin but to accumulation of intracellular virions from around 20 minutes postinduction. When a rifampicin-resistant lysogen was induced in the presence of the antibiotic, no inhibition of RNA synthesis was detected, although a smaller population of progeny than in control cultures without rifampicin was obtained. Two possible explanations of this fact are discussed.