FIG. 1.

Analysis of the replication mechanism of pSF118-20. (A) Cell lysates of L. salivarius LS201 strains harboring pLS203 (an E. coli-Lactobacillus shuttle vector containing the replication origin of pSF118-20) or pVE6007 (a rolling-circle replication plasmid with pWV01 origin) with or without nuclease S1 treatment were electrophoresed on a 0.8% agarose gel. The PCR product of repA₂₀ (LSL_1965) and NcoI-digested pVE6007 were used as probes to hybridize against blots prepared from either a denatured gel (B) or a nondenatured gel (C). Lane 1, pLS203; lane 2, pVE6007; lane SM, supercoiled DNA ladder (Sigma); lane M, linear DNA ladder (Bioline); −, untreated DNA sample; +, nuclease S1-treated DNA sample; SS, single-stranded DNA intermediates (indicated by arrows in the nuclease S1-treated DNA sample lane). The background smear in panel B represents degraded plasmid DNA.