FIG. 2.

Effects of H₂O₂ on catalase activity and katA gene expression in the parental Rm1021 and the mutant RmoxyR strains. Bacteria were treated (+) or not (−) with 1 mM H₂O₂ for 1 h. Cell extracts were prepared and analyzed for catalase activities spectrophotometrically (A) and on a native polyacrylamide gel (B), using 30 μg of protein per lane and determined with a protein assay kit (Bio-Rad Laboratories GmbH). The positions of KatA and KatB are indicated as described by Sigaud et al. (36). Catalase activities were obtained with triplicate samples from two independent experiments and are given in units per milligram of protein. Data are presented as the means ± standard deviations of results. The expression of the katA gene was monitored using Northern blot (C) and primer extension (D) analyses.