GENETIC-ANALYSIS OF REGIONS OF THE LACTOCOCCUS-LACTIS SUBSP LACTIS PLASMID PRS01 INVOLVED IN CONJUGATIVE TRANSFER

The genes responsible for conjugative transfer of the 48.4-kb Lactococ cus lactis subsp. lactis MW plasmid pRSO1 were localized by insertiona l mutagenesis. Integration of the IS946-containing plasmid pTRK28 into pRSO1 generated a pool of stable cointegrates, including a number of plasmids altered in conjugative proficiency. Mapping of pTRK28 inserti ons and phenotypic analysis of cointegrate plasmids identified four di stinct regions (Tra1, Tra2, Tra3, and Tra4) involved in pRSO1 conjugat ive transfer. Tra3 corresponds closely to a region previously identifi ed (D. G. Anderson and L. L. McKay, J. Bacteriol. 158:954-962, 1984). Another region (Tra4) was localized within an inversion sequence shown to correlate with a cell aggregation phenotype. Tra1 and Tra2, two pr eviously unidentified regions, were located at a distance of 9 kb from Tra3. When provided in trans, a cloned portion of the Tra3 region com plemented Tra3 mutants.