The use of oriC-dependent phage infection to characterize the ultra violet (UV)-induced inhibition of initiation of DNA replication in Escherichia coli

Abstract

The oriC transducing phage λporiCC is a pseudovirulent phage capable of forming plaques on a λ lysogen. This phenotype is dependent upon the presence of the oriC insert. The ability of λporiCC to form plaques on a λ lysogen represents a potential phage assay system for studying aspects of oriC function. In the present study we establish that λporiCC infection of a λ lysogen is a legitimate assay for oriC function. We use this assay to confirm the previously reported observation that initiation of DNA replication from oriC is transiently inhibited in a ultra violet (UV) irradiated cell at doses greater than 60 J/m2. We further demonstrate using this assay that the UV induced inhibition of initiation of DNA replication from oriC is not a SOS function nor a heat shock function. In the course of these studies, we found that λporiCC infection of a non-lysogenic cell is extremely sensitive to pre-irradiation of the Escherichia coli host. We postulate that the sensitivity of λporiCC replication to host cell pre-irradiation reflects in some way the transient inhibition of initiation of DNA replication from oriC following UV irradiation.