SCP1-dependent Weigle activation of the VP5 phage in Streptomyces coelicolor A3(2).

The kinetics of induction of the UV-irradiated bacteriophage VP5 (Weigle reactivation) in Streptomyces coelicolor A3(2) strains with and without plasmid was investigated. Chloramphenicol (CAF) inhibits Weigle reactivation (WR) in UF strains (SCP1 absent) but not in SCP1+ strains of IF fertility (free plasmid). CAF, moreover, inhibits protein synthesis in non-irradiated UF and IF strains. In UV-irradiated IF strains, on the other hand, protein synthesis takes place irrespective of CAF. Weigle reactivation appears to require protein synthesis: the SCP1 plasmid, by protecting protein synthesis from CAF inhibition in UV-irradiated strains, allows WR. The proteins synthesized after UV induction during the pre-incubation period were investigated and the results suggest that a new UV-induced protein, coded by a gene localized on the plasmid, interacts with the cellular SOS system.