CHARACTERIZATION OF LAMBDA-POLA TRANSDUCING PHAGES - EFFECTIVE EXPRESSION OF THE ESCHERICHIA-COLI POLA GENE

λpolA phages carrying the polA gene in either orientation were isolated and characterised by genetic tests and by assay of the polA gene product after infection of E. coli or induction of lysogens. Lytic infection gave consistently better amplification of DNA polymerase I than that obtained by induction of a lysogen. Optimal amplification of DNA polymerase I was not achieved from the PL promoter of cro-phages, but some advantage accrued when the polA gene was oriented for transcription from the PL promoter of a cro+ phage. λpolA phages in which the polA allele was from E. coli strain C600 provided between amplification than phages with the polA allele from E. coli ED8659. Induction of a {black left-pointing small triangle}polAlcI857 Qam Sam prophage gave levels of DNA polymerase I approaching 100 times that found in the non-lysogenic Pol+ host. Genetics studies with the λpolA phages confirmed the previously postulated orientation of the polA gene within the E. coli genome. © 1979 Springer-Verlag.