Pleiotropic effects of a DNA adenine methylation mutation (dam-3) in Escherichia coli K12

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology



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Medical Subject Headings

Adenine; Centrifugation, Zonal; Coliphages; Conjugation, Genetic; DNA Repair; *DNA, Bacterial; DNA, Viral; Escherichia coli; Lysogeny; Mesylates; Methylation; Molecular Weight; *Mutation; Phenotype; Radiation Genetics; Transduction, Genetic; Ultraviolet Rays


The dam-3 mutation results in a five-fold reduction in the number of 6-methyl-adenine (6-meA) residues in the DNA of E. coli K12 or phage lambda. The DNA of phage fd appears to be devoid of 6-meA when propagated on dam-3 bacteria. The phenotypic differences between dam-3 and dam+ bacteria include: (i) increased free phage in lysogenic dam-3 cultures, (2) increased sensitivity to methyl methanesulfonate (MMS), (3) inviability of dam-3 lex-I strains, (4) lower molecular weight of DNA in dam-3 bacteria in the absence of DNA ligase and (5) increased rate of DNA degradation in dam-3 recA strains.

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Citation: Mutat Res. 1975 Apr;28(1):15-26.

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