Figure 3

Survival of wild type L. hongkongensis HLHK9 and derivative mutants under acidic conditions. Survivors were enumerated by plating serial dilutions on BHA plates. Error bars represent means ± SEM of three independent experiments. An asterisk indicates a significant difference (*, p < 0.05; **, p < 0.01; ***, p < 0.001). A, Survival of HLHK9 and HLHK9∆ureA in the presence of 50 mM urea. B, Survival of HLHK9, HLHK9∆arcA1, HLHK9∆arcA2 and HLHK9∆arcA1/arcA2 in the presence of 50 mM arginine. C, Survival of HLHK9, HLHK9∆ureA, HLHK9∆arcA1/arcA2 and HLHK9∆ureA/arcA1/arcA2 in the presence of 50 mM each of urea and arginine. D, Survival of HLHK9, HLHK9∆ureA, HLHK9∆arcA1/arcA2 and HLHK9∆ureA/arcA1/arcA2 at pH 4, and at the indicated time points, in the presence of 50 mM each of urea and arginine.