FIG 2.

Loss of SMU_833 did not affect acid tolerance but reduced the ability to resist oxidative stress. Wild-type (WT), smu_833 mutant (833–), and complemented (833–/+) strains were grown to early exponential phase, washed with 0.1 M glycine (pH 7.0), and then resuspended in either 0.1 M glycine buffer (pH 2.8) for acid killing (A) or 0.1 M glycine buffer (pH 7.0) with 0.2% hydrogen peroxide (B). The data are averages of three independent experiments. Error bars represent the standard deviations, but are not depicted if the value was 0 or a negative number. Statistical analysis was performed using a Student t test to compare the means of two samples. Comparison of WT and mutant (833–) strains: 15 min, P < 0.05; 30 min, P < 0.01.