[Mobilization of Vibrio cholerae chromosomal genes by plasmid RP4::Mu cts62].

The RP4::Mu cts62 plasmid was constructed in Escherichia coli cells and subsequently transferred by conjugation into the cells of Vibrio cholerae. This plasmid had been shown to mobilize chromosomal genes of V. cholerae during intrageneric matings. The frequency of mobilization is higher in matings at 37 degrees C, the temperature which is semipermissive for temperature sensitive Mu cts62 phage. This is only true for strains harbouring RP4::Mu cts62, but not for strains containing the RP4 plasmid. Frequencies of mobilization per transferred plasmid exceeded conspicuously the known frequency for the mobilizing activity of the P-factor of V. cholerae. Transconjugants selected for chromosomal markers carried no traces of RP4 plasmid or Mu cts62 markers. This feature of their use in the genetical analysis of V. cholerae. Reasons for the absence of plasmid markers in recombinants are being discussed.