FIG. 4.

Essential role of comB6 for transformation competence as revealed by deletion and complementation studies. (A) Precise deletions of comB6 (hp0037) or the region comprising comB6 to comB10 (hp0037 to hp0042) were constructed by replacing the corresponding gene sequences with a cat or a kanamycin (aphA-3) resistance gene cassette, respectively. (B) Complementation of the corresponding genes was obtained by cloning the comB6 to comB10 or the comB7 to comB10 genes in the shuttle vector pHel2 behind the H. pylori flaA promoter (plasmid pDH80) to result in pAK24 or pDHO46 (25), respectively. The shuttle plasmids were transferred into strain P228 (P1ΔcomB6-comB10::aphA-3). The competence for genetic transformation of the corresponding strains is indicated at right (+ or −). For quantitative data of transformation experiments, see Table 3.