Effect of mutations in the htrA gene of C. jejuni on adherence to and invasion of INT407 human intestinal epithelial cells. Adhered (A), invaded (B), and viable (C) bacteria of C. jejuni NCTC11168 (wt), LB1281 (ΔhtrA) and KB1025 (htrA S197A) expressed as percentage of the inocula. Values represent the average and standard deviation of results from four wells in two independent experiments. Dashed line show the limit of detection for the ΔhtrA mutant. The p values are calculated using Student's t-test. p values are obtained by comparing each mutant to the wild type. In Panel A, the two mutants are also compared as indicated in the figure.