FIG. 6.

Induction of PerR regulon genes by H₂O₂. Strains containing the indicated reporter fusions were grown in minimal medium with no added Mn(II) or Fe(III) (None) or with 10 μM Fe(III) (Fe), 5 μM Mn(II) (Mn), or both (Fe+Mn) as described in the legend to Fig. 3. At 2 h after resuspension, the cultures were split and 100 μM H₂O₂ was added to one sample. After growth for another 30 min, cells were harvested for β-Gal assay and induced expression (gray bars) was compared to expression in the absence of H₂O₂ addition (white bars). Note that the data represented by the white bars are the same as those for the 2.5-h time point in Fig. 3. Experiments were performed twice; error bars represent the standard error of the mean.