Recombinant levels of Escherichia coli K-12 mutants deficient in various replication, recombination, or repair genes

Abstract

E. coli strains containing mutations of lexA, rep, uvrA, uvrD, uvrE, lig, polA, dam or xthA were constructed and tested for conjugation and [phage P1] transduction proficiencies and ability to form Lac+ recombinants in an assay system utilizing a nontandem duplication of 2 partially deleted lactose operons (lacMS286.vphi.80dIIlacBK1). lexA and rep mutants were as deficient (20% of wild type) as recB and recC strains in their ability to produce Lac+ progeny. All the other strains exhibited increased frequencies of Lac+ recombinant formation, compared with wild type, ranging 2- to 13-fold. Some strains showed markedly increased conjugation proficiency (dam uvrD) compared to wild type, while others appeared deficient (polA107). Some differences in transduction proficiency were also observed. Analysis of the Lac+ recombinants formed by the various mutants indicated that they were identical to the recombinants formed by a wild-type strain. Genetic recombination in E. coli is apparently a highly regulated process involving multiple gene products.