Figure 1.

Detection of plasmid-specific regions in 19 B. B31 clones by PCR. PCRs were performed under standard conditions, with annealing temperatures at 2°C below the lowest primer T_m (see supplemental data). Ten-microliter samples of each reaction were electrophoresed in 1.5% agarose gels and visualized by ethidium bromide staining (21). H, I, L, high, intermediate, and low infectivity, respectively. In all, present in all 19 Bb B31 clones. No effect, PCR detection of plasmid had no apparent correlation with infectivity in mice under the conditions used in this study.