Physical mapping of the conjugative plasmid pMB1-1 of Enterococcus faecalis

The sexpheromone system of Enterococcus faecalis is a form of bacterial conjugation that plays an important role in the horizontal dissemination of genes. The ecological significance of 'sexual' plasmids is to permit a rapid mobilization of genes of interest for the species (e.g. those encoding haemolysins, bacteriocins or antibiotic resistance). The physical mapping of pMB1-1, a conjugative plasmid of Ent. faecalis that responds to cCF10 pheromone, has been undertaken. By means of hybridization with conserved sequences of pCF10 plasmid, the regions harbouring the genes responsible for the pheromone inhibitor and the aggregation and exclusion proteins of this plasmid have been identified. The results demonstrated that plasmids pMB1-1 and pCF10 only show homology in the region involved in the conjugative response, suggesting that this region may be transferred in an independent way to that of the rest of the plasmid.