FIG 5.

Catalase activity in S. meliloti stains deleted for alternative sigma factors. (A) Total catalase activity of various alternative sigma factor deletions with and without 30 min of treatment with 1 mM H₂O₂. Catalase activity was normalized to OD₆₀₀. Error bars indicate standard deviations. “a” indicates a P value of ≤0.05 compared to 0 mM H₂O₂. “b” indicates a P value of ≤0.05 comparing the activity of the mutant strain at 0 mM H₂O₂ to the activity of the wild-type strain at 0 mM H₂O₂. Experiments were performed in triplicate. (B) Activity of katA-uidA transcriptional fusion with and without 30 min of treatment with 1 mM H₂O₂. Error bars indicate standard deviations. *, P ≤ 0.05 (comparing the activity of the mutant strain at 0 mM H₂O₂ to the activity of the wild-type strain at 0 mM H₂O₂). Experiments were performed in triplicate.