Absence of Ultraviolet-inducible DNA Polymerase I-like Activity in Escherichia coli Strains Harbouring R Plasmids

1 Microbiology Section, Department of Pharmaceutics, The School of Pharmacy, University of London, Brunswick Square, London WCIN1AX, U.K. ABSTRACT No DNA polymerase I-like activity was found associated with the ultraviolet (u.v.)-protecting plasmids R205. R46 or pKM101 in either uninduced or u.v.-induced wild-type or DNA polymerase I-deficient strains of Escherichia coli. Nor was any plasmid-associated polymerase activity detectable in similar systems containing u.v.-irradiated DNA as template. However, plasmids R205, R46 and pKM101 still increased survival and mutagenesis of the polymerase I-deficient E. coli strain after u.v. irradiation.