Characterization of a Mutant Bacteriophage that Overcomes An Antitermination Defect in E. coli RNA

Mutations in the highly conserved zinc-binding domain of the β’ subunit of E.coli RNA polymerase prevent the growth of phage that use a unique RNA-based mechanism of transcription antitermination. Here, we describe the isolation and characterization of a mutant phage that overcomes this block. The genome of the mutant only differs from the parental phage by 2 nucleotides. Close inspection of the sequences surrounding the mutation suggested that a new promoter had been created. This was confirmed by cloning the potential promoter sequences into a promoter probe expression vector. We hypothesize that the new promoter permits the expression of phage genes that are essential for growth on the mutant bacterial host