FIG. 3.

Detection of ssDNA plasmid intermediates. Plasmid DNA was extracted from L. lactis and Lactobacillus strains carrying either pCP12 or pWX2. The extracts were then either treated (+) or not treated (−) with S1 nuclease. Plasmid extracts containing pWC1 and pGT232-based recombinant plasmids were blotted onto nylon membranes and probed with radioactively labelled pWC1 and pWX2 plasmid DNA, respectively. Lanes: W, L. lactis MG1363(pCP12); 1, L. salivarius subsp. salicinius ATCC 11742(pWX2); 2, L. reuteri DSM 20016(pWX2); 3, L. lactis MG1363(pWX2); 4, L. reuteri 100-23(pWX2); 5, L. reuteri 100-23C(pWX2); P, plasmid pWX2 purified from E. coli (positive control). The different topological forms of double-stranded plasmid DNA (supercoiled [SC], linear [LI], and open circular [OC]) are indicated. The position of the ssDNA intermediate of pCP12 is also shown.