Isolation and characterisation of Hfr strains from a recombination-deficient strain of Escherichia coli

Summary A T6^s RecA^- strain carrying a lac proB deletion and F_ts lac ⁺ was challenged with phage T6 and survivors which were both T6^r and Lac⁺ at 42° were tested for fertility. Among these were a number of Hfr strains which had their points of origin at or near the tsx locus and which still carried the recA allele. These arose in comparable frequencies in the RecA^- strain and in a Rec⁺ analogue. We conclude that such integration does not require the RecA function. The rate of chromosome transfer was similar in one such RecA^- Hfr and its Rec⁺ derivative; the yield of recombinants from the RecA^- strain was slightly lower than from its Rec⁺ derivative.