title: Mutants of Salmonella typhimurium deficient in DNA polymerase I: further characterization and genetic analysis.
abstract: Tests with a plasmid-borne ochre suppressor (sup-812) and a chromosomal amber suppressor (supD501) revealed that one of three mutants of S. typhimurium deficient in DNA polymerase I was an amber mutant. Assays performed on crude extracts established that derivatives of this mutant (designated polA3) carrying ochre and amber suppressors had about 13 to 20% respectively of the enzyme activity found in the wild-type parent. The unsuppressed mutant showed less than 1% of the wild-type level of activity. Other properties of the polA3 mutant that were also partially or in some cases completely reversed by the sup-812 and supD501 suppressors included: u.v. sensitivity, methyl methanesulphonate (MMS) sensitivity, reduced ability to effect host-cell reactivation of u.v.-irradiated or MMS-treated bacteriophages, inability to maintain the (Col El) plasmid, and reduced ability to plate the phage mutant P22 c2 hpi-308. Mapping by P1-mediated transduction showed that all three polA mutations lie between metE and rha on the S. typhimurium chromosome, and that the polA mutation is cotransduced with metE at a frequency of 20% and with rha at a frequency of 8%.
mesh_terms: D002874:Chromosome Mapping; D004254:DNA Nucleotidyltransferases / Q000172:deficiency*; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009154:Mutation; D010957:Plasmids; D011830:Radiation Effects; D012483:Salmonella Phages; D012486:Salmonella typhimurium / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects; D013489:Suppression, Genetic; D014466:Ultraviolet Rays
chemical_list: D008741:Methyl Methanesulfonate; D004254:DNA Nucleotidyltransferases