title: A conditional lethal mutant of Escherichia coli K12 defective in the 5' leads to 3' exonuclease associated with DNA polymerase I.
abstract: A mutant strain of E. coli, initially identified by an abnormally high frequency of recombination, has been found to be defective in the 5' --> 3' exonuclease associated with DNA polymerase I, but not in the polymerase activity. This defect is tolerated at 30 degrees , but is lethal at 43 degrees . Like other polymerase I mutants, the strain is unusually sensitive to methyl methanesulfonate and to ultraviolet irradiation; it is also unable to support the growth of phage lambda defective in general recombination, and shows a reduced rate of joining of 10S "Okazaki fragments." These results demonstrate that a functional DNA polymerase I is essential for normal growth and viability in E. coli K12.
mesh_terms: D002384:Catalysis; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D003090:Coliphages / Q000201:enzymology; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D005092:Exonucleases / Q000378:metabolism*; D005796:Genes; D005804:Genes, Lethal; D009154:Mutation; D011830:Radiation Effects; D011995:Recombination, Genetic; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D004254:DNA Nucleotidyltransferases; D005092:Exonucleases