FIG 4.

Analysis of cagC mutants. A marked cagC mutant strain (containing an antibiotic cassette inserted in cagC), unmarked cagC mutant, and complemented mutant were generated as described in Materials and Methods. (A) Production of CagC and a control protein (HspB) was assessed by immunoblot analysis. (B) AGS cells were infected with the indicated strains of H. pylori, and IL-8 secretion was quantified by ELISA of cell culture supernatants. *, P < 0.01 in comparison to findings for the parental strain (Student's t test). (C to H) H. pylori strains were cocultured with AGS cells, and pilus formation was then analyzed by SEM. Panels C to E show the cagC marked mutant. Panels F to H show the cagC unmarked mutant. (I) Number of pili visualized per bacterium. Bars, 1 μm. Arrows point to pili.