Characterization of DNA adenine methylation mutants of Escherichia coli K12

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology



Document Type


Medical Subject Headings

Adenine; Conjugation, Genetic; DNA (Cytosine-5-)-Methyltransferase; DNA, Bacterial; Escherichia coli; Genotype; Methyltransferases; *Mutation; Phenotype; Recombination, Genetic; Transduction, Genetic


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.

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Citation: Mutat Res. 1979 Feb;59(2):157-65.

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