Characterization and restriction analysis of the P sex factor and the cryptic plasmid of Vibrio cholerae strain V58.

The P plasmid of Vibrio cholerae is a derepressed sex factor restricted to V. cholerae and has been shown to express surface exclusion. We have isolated the plasmids of strain V58 and have found that in addition to P, two further cryptic plasmids are also present. P has a size of 68 kb as determined by both electron microscopy and restriction endonuclease analysis. These other plasmids are 34 and 4.7 kb in size. Restriction maps of P and the larger cryptic plasmid have been determined. It has been demonstrated that P differs from the standard Inc group test plasmids and also expresses a surface exclusion system. The ability of the type Inc plasmids to be transferred to V. cholerae by either liquid or filter matings and the stability of these plasmids in V. cholerae have also been examined.