title: DNA polymerase I-dependent mutants of coliphage lambda.
abstract: Mutagenized lysates of bacteriophage lambda were screened for mutants unable to plate on DNA polymerase I-deficient (polA(-)) hosts. The mutants obtained were all recombination deficient (red(-)). These mutants, like red(-) and gam(-) mutants previously isolated by others, grow more poorly than wild-type lambda even on polA(+) hosts (burst size 14 to 30% of wild-type lambda.) In a polA(-) host, the burst size of red(-) and gam(-) mutants is reduced an additional five- to tenfold, and lysis is delayed. Wild-type lambda grows normally in polA(-) hosts. Neither lambdaN(-)nin (which doesn't express red or gam) nor lambdabio phages (from which all or part of the red-gam region is deleted) form plaques on polA(-) hosts. Apparent revertants, able to plate on polA(-) hosts, have been selected from both lambdaN(-)nin and lambdabio. Those derived from N(-)nin seem to be N(-)nin cro(-) mutants; whereas those coming from lambda bio have a new bypass mutation (pas) that lies between genes P and Q.
mesh_terms: D002874:Chromosome Mapping; D003090:Coliphages; D004254:DNA Nucleotidyltransferases; D004267:DNA Viruses; D004926:Escherichia coli / Q000201:enzymology*; D008040:Genetic Linkage; D009154:Mutation; D011995:Recombination, Genetic
chemical_list: D004254:DNA Nucleotidyltransferases