Conjugal mobilization of streptococcal plasmid pMV158 between strains of Lactococcus lactis subsp. lactis

pMV158, a non-self-transmissible plasmid encoding tetracycline resistance, was conjugally transferred from Enterococcus faecalis JH203 to Lactococcus lactis subsp. lactis IL1403. This transfer appeared to be dependent on the cotransfer of the conjugative plasmids pAMβ1 or pIP501. Intraspecies conjugal transfer of pMV158 also occurred in strain IL1403. In contrast to the transfer from E. faecalis, transfer in IL1403 did not require the presence of a conjugative plasmid in the donor strain but, rather, appeared to be dependent on putative chromosomal functions in strain IL1403. The transfer of pMV158 from strain IL1403 required the presence of an active pMV158-encoded protein, which showed homology to the Pre (plasmid recombination enzyme) proteins encoded by several small plasmids extracted from Staphylococcus aureus, such as pT181.