FIG 1.

Both the catalase HktE and the peroxidase PgdX protect NTHI strain 86-028NP from H₂O₂-induced oxidative stress. Strains of 86-028NP that lacked either hktE (A) or pgdX (B) were grown exponentially and then treated with 500 μM H₂O₂ for 10 min. The cells were harvested and plated to assess viability relative to that of the parent strain. Loss of hktE produced a slight but significant loss in cell viability, while the strain that lacked pgdX exhibited increased viability. Complementation of the mutated gene restored the parental phenotype in both cases. Error bars show standard errors of the means. *, P ≤ 0.05; **, P ≤ 0.01; ****, P ≤ 0.0001 (n = 9 [A]; n = 6 [B]).