Genetic Analysis of Regions Involved in Replication and Cadmium Resistance of the Plasmid pND302 fromLactococcus lactis

The 8.8-kbLactococcus lactisplasmid pND302 encodes resistance to cadmium (CdR). Regions of pND302 involved in replication and CdRwere subcloned and sequenced. The replication region is localized on a 1.5-kb region and consists of an open reading frame (repB) preceded by a noncoding AT-rich sequence (ori) which is highly homologous to lactococcal theta-type replicons. The CdRdeterminant is localized on a 2.9-kb region and encodes putative proteins similar to the Cd2+-specific P-type efflux ATPase (CadA) and the transcriptional regulatory repressor (CadC) identified inStaphylococcus aureus, Bacillus firmus,andListeria monocytogenes.Similar CdRdeterminants were also detected by PCR in other CdRplasmids isolated from differentL. lactisstrains.