Site-specific recombination at oriT of plasmid R1162 in the absence of conjugative transfer

R1162 is efficiently comobilized during conjugative transfer of the self-transmissible plasmid R751. Bacteriophage M13 derivatives that contain two directly repeated copies of oriT, the site on R1162 DNA required in cis for mobilization, were constructed. Phage DNA molecules underwent recombination during infection of Escherichia coli, with the product retaining a single functional copy of oriT. Recombination was strand specific and depended on R1162 gene products involved in mobilization, but did not require the self-transmissible plasmid vector. Two genes were identified, one essential for recombination and the other affecting the frequency of recombination. Recombination of bacteriophage DNA could form the basis of a simple model for some of the events occurring during conjugation without the complexity of a true mating system.