Molecular and General Genetics MGG

, Volume 199, Issue 3, pp 518-523

First online:

Rec-dependent and Rec-independent recombination of plasmid-borne duplication in Escherichia coli K12

  • Mark MatfieldAffiliated withDept. of Microbiology, University of Leicester
  • , Randa BadawiAffiliated withDept. of Biochemistry, University of Leicester
  • , William J. BrammarAffiliated withDept. of Biochemistry, University of Leicester

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Plasmidic recombination in E. coli K12 has been previously demonstrated to be dependent on the host rec genotype. The construction of plasmids that carry a duplication within an antibiotic-resistance gene is described. Recombination between the direct repeats recreates an active antibiotic-resistance gene, allowing quantitative analysis of recombination frequencies in a closely related set of E. coli K12 strains carrying various rec mutations. Using this system, intraplasmidic recombination of a duplication within the pBR322 tetracycline-resistance gene is shown to be rec-dependent while recombination of a similar duplication within the kanamycin-resistance gene of Tn903 is shown to be independent of recA, recB, recC, recE, recF and sbcB.