Fig. 3.
ClcA affects survival fitness in acidic and alkaline environments in a chloride-dependent manner. Results are shown as the competitive index (CI) for colonization experiments comparing the following strains: ∆clcA to a fully virulent ∆lacZ (black circles), ∆clcA with empty vector (p) to ∆lacZ with empty vector (p, gray filled black circles), ∆clcA constitutively expressing clcA from a plasmid (∆clcA pclcAc) to ∆lacZ carrying the empty vector (p, blue triangles), or ∆clcA pclcAc to ∆clcA∆lacZ with empty vector (p, red squares). (A and B) In vitro competitions were performed for 1 to 4 h as indicated in LB adjusted to pH 5, 7, or 9 using HCl or NaOH, respectively. (C) Competitions were performed in vitro (LB, pH 7) or in vivo using the infant mouse model. (D and E) In vitro competitions were performed for 4 h in LB with various chloride concentrations adjusted to pH 5, 7, or 9 using H3PO4 or NaOH, respectively. Different chloride concentrations were achieved by addition of no NaCl (low chloride), 171 mM NaCl (regular), or 750 mM NaCl (high chloride), respectively. Each circle represents the CI from a single assay (n ≥ 6), the horizontal bars indicate the median of each dataset, and the asterisks indicate significant differences (P < 0.05) using either a Wilcoxon signed-rank test to indicate CIs significantly different to hypothetical value of 1 (A) or a Kruskal–Wallis test followed by post hoc Dunn’s multiple comparisons (B–E).