High frequency transduction of R-factor encoded gentamicin resistance by bacteriophage P1Cm.

No transposition of plasmid-coded gentamicin resistance from more than fifty different R-plasmids onto a deletion derivative of bacteriophage lambda was found. In contrast, 13 out of 17 R-plasmids gave rise to the formation of high frequency transducing (hft) hybrids of phage P1Cm. All the hft P1Cm derivatives transduced other antibiotic resistances in addition to gentamicin resistance. The DNA sequences found to be integrated in the prophage genomes of hft phages were generally longer than 15 kb, and ranged up to 60 kb. In most cases analyzed the points of insertions were close to the IS1 elements resident in P1Cm. In part of the hybrid phages the entire R-plasmids were cointegrated. One plasmid (pWP14a) cointegrated preferentially into a Bg1II fragment of P1Cm containing an invertible structure (C-loop). Eleven out of 16 R-plasmids showed homology to IS1.