FIG. 1.

(a) Plasmid profiles of transconjugant lactococcal strains demonstrating the sequential buildup of phage resistance systems leading to the construction of the strain DPC5000. Lanes: 1, molecular size markers from DRC3 (18); 2, MG1614; 3, DPC3343(pAH82); 4, DPC3290(pAH90); 5, DPC5012(pMRC01); 6, DPC5002(pMRC01, pAH82); 7, DPC5001(pMRC01, pAH90); 8, DPC5000(pMRC01, pAH90, pLP712); 9, DPC5013(pLP712); 10, NCDO712 (contains pLP712 and other native plasmids). The position of the chromosomal band (Chrom.) is indicated. (b) Gel obtained by PCR using pMRC01-specific primers indicating the presence of the pMRC01 plasmid. Lanes are the same as those in panel a except with Lambda BstEII replacing DRC3 as the molecular mass standard (lane 1).