FIG. 3.

Deletion frequency of H. pylori wild-type and ruvB mutant strains. The chloramphenicol/kanamycin resistance cassette flanked by identical repeats of 0 (control), 50, or 100 bp, as described by Aras et al. (3), was inserted into vacA (control) or ruvB, and deletion frequencies calculated, as described previously (3). As expected, no deletions were detected (*, frequency of <10⁻⁸) for the strains with the 0-bp cassette, and strains with the cassette in vacA or ruvB showed progressively higher deletion frequencies with increasing size of the identical repeats. Strains with the 50-bp or 100-bp deletion cassette in ruvB display significant (P < 0.05) seven- and fourfold decreases, respectively, in deletion frequency compared to the control (vacA) with comparable cassettes. Bars represent means ± standard deviations from ≥6 replicate experiments.