Isolation of a nontransmissible antibiotic resistance plasmid by transductional shortening of R factor RP1

A plasmid segregant carrying tetracycline and carbenicillin resistance markers has been isolated from R factor RP1 by transductional shortening with phage P22. The new plasmid RP1-S2, which has a molecular weight of 23 times 10-6, has lost the transfer, phage sensitivity, and neomycin resistance functions of RP1. It combines readily with a W group plasmid, R388, to form a transmissible carbenicillin and trimethoprim resistance plasmid, RWP1.