The Effect of a Drug-resistance Factor on Recombination and Repair of DNA in Escherichia coli K12

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Abstract
The presence in recipient strains of E. coli K12 of the plasmid R46 greatly reduced the yield of recombinants from crosses with several Hfr strains and virtually abolished the formation of recombinants by [phage] P1 transduction without significantly affecting the transfer of the F prime from a strain carrying Fgal. The R46 plasmid had paradoxical effects on mutability: it appeared to enhance the yield of mutants following irradiation with UV light but it reduced the number of mutants detectable in unirradiated cultures. The effects of this plasmid on UV light survival of the wild type and several mutants defective for recombination and repair were measured and the results, in the main, confirm similar observations by others. Not only is the survial of the strain harboring R46 greater than that of the parent strain in all the cases studied, but the survival of UV irradiated bacteriophage .lambda. is also greater.