title: Method for isolating restriction- and modificationless mutants of Escherichia coli K-12.
abstract: A simple method is described for the selection and isolation of restriction- and modificationless mutants in Escherichia coli K-12 by using the following properties: (i) the temperature-sensitive repressor activity of phage lambdacI857; (ii) a mutant of lambda phage defective in integration and the establishment of repression (lambdab2cI); (iii) a virulent lambda phage insensitive to the repressor activity. The final yield of spontaneously arising rk-mk+ and rk-mk- mutants from stationary-phase cultures was about 5% of the surviving cells.
mesh_terms: D003090:Coliphages / Q000235:genetics / Q000254:growth & development; D004279:DNA, Viral / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D005809:Genes, Regulator; D005814:Genes, Viral; D008242:Lysogeny; D008722:Methods; D009154:Mutation; D010948:Viral Plaque Assay
chemical_list: D004279:DNA, Viral