Dioxygen tolerance.

<p>The resistance to dioxygen was assayed by counting colony-forming units of bacterial cells suspended in PBS with yeast extract (5 g/l) and maintained in an aerobic atmosphere for six hours. Wild type (■), <i>cydAB</i> mutant (▲) and complemented <i>cydAB</i> mutant (●). Bars represent standard errors and asterisks indicate statistically significant differences between values of wild-type strain and mutant or complemented mutant strains (* p<0.05). Statistical analysis were performed with GraphPad Prism software (California, USA). The Mann-Whitney test was used and p-values<0.05 were considered significant.