title: Characterization of DNA adenine methylation mutants of Escherichia coli K12.
abstract: The phenotypic traits of 7 independently isolated dam mutants of Escherichia coli have been examined. The mutant strains differ from the wildtype in the following respects: (1) decreased DNA adenine methylase activity in vivo and in vitro; (2) a 14--85-fold increase in spontaneous mutability; (3) decreased survival after ultraviolet irradiation; (4) a 10--21-fold increase in spontaneous induction of lambda phage from lysogens; (5) a 3--17-fold increase in the level of recombination; and (6) inviability of double mutants containing dam- and recB- or recC-. Unmethylated fd phage chromosomes are able to replicate normally in dam- mutants. A mutant strain in which the dcm gene is deleted is viable, showing that the dcm gene product is dispensible for growth.
mesh_terms: D000225:Adenine / Q000378:metabolism; D003227:Conjugation, Genetic; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D005838:Genotype; D008780:Methyltransferases / Q000235:genetics*; D009154:Mutation; D010641:Phenotype; D011995:Recombination, Genetic; D014161:Transduction, Genetic
chemical_list: D004269:DNA, Bacterial; D008780:Methyltransferases; D004248:DNA (Cytosine-5-)-Methyltransferases; D000225:Adenine