Behavior of Some Episomal Elements in a Recombination-Deficient Mutant of Escherichia coli¹

Abstract

Conjugal transfer and autonomous replication of some episomes occurred normally in a recombination-deficient (Rec^-) mutant of Escherichia coli K-12. Transduction with phage Plbt of an R factor also occurred normally in this Rec^- mutant, but complete or abortive transduction with Plbt of chromosomal genes did not occur. In contrast, transduction of galactose genes by phageλdg occurred in the Rec^- bacteria as frequently as in the Rec⁺ strain. It was shown that phage Plbt does not grow at all on the Rec^- bacteria. Recombination between two different R factors, two mutants of phage y and two mutants of phage T4 occurred normally in the Rec^- bacteria, but did not give a Rec⁺ phenotype to the host bacteria. Colicinogenic factor I made the Rec^- host bacteria more resistant to ultraviolet light but the colicinogenic strain was still infertile in the crosses with the Hfr Brains of E. coli K-12.