Nucleic Acid Sequence and Affiliation of pLUG10, a Novel Cadmium Resistance Plasmid fromStaphylococcus lugdunensis

Abstract

Tolerance ofStaphylococcus lugdunensisto relatively high levels of cadmium is mediated by a 3117-bp plasmid, pLUG10. Sequencing reveals three major open reading frames (ORFs) in a single orientation. One ORF encompasses the origin of replication and its predicted product (RepL; 350 amino acids (aa)) shows 70% homology in its deduced aa sequence with Rep proteins of the pT181 family. A lagging strand conversion signal (palA) very similar to that of class I plasmids is present outside therep–orilocus. The other two ORFs of 209 and 116 aa show 92.5% homology between their deduced aa sequences and the CadB and CadX peptides from the pOX6 plasmid ofStaphylococcus aureus.The CadX-like peptide is 40% homologous to theS. aureusCadC product. Deletion of the C-terminalcadXgene by restriction enzyme digestion or frame-shift inactivation of thecadBgene reduced, but did not completely abolish, cadmium resistance. The two gene products may act cooperatively to confer cadmium resistance inS. lugdunensis.