FIG 4.

Gene expression analysis of pmtA and H₂O₂ stress sensitivity. (A) 5448 WT was grown in the presence of Fe(II) or 2,2′-dipyridyl, and gene expression of pmtA was analyzed. (B) 5448 WT, 5448ΔperR, and 5448ΔperR::perR cells grown at 37°C to mid-exponential phase (OD₆₀₀ = 0.6 to 0.8) were challenged with water (control), 5 mM H₂O₂, or 8 mM Fe(II) for 30 min. pmtA gene expression was analyzed by qPCR using gyrA as the reference gene. Data represent the mean ΔΔC_q (log₂) values ± standard deviations from 3 independent biological replicates (2-way ANOVA was used for all comparisons to the control for each strain [*, P < 0.05; ** P < 0.01; ***, P < 0.001]). (C to F) Growth curve analysis of 5448 WT, 5448ΔpmtA, and 5448ΔpmtA::pmtA in hydrogen peroxide. Strains were grown in THY broth plus 2 mM Fe(II) to mid-exponential phase (OD = 0.6 to 0.8) and diluted to an OD₆₀₀ of 0.05 in THY broth with 0.00 mM (C), 1 mM (D), 2 mM (E), or 3 mM (F) H₂O₂. Growth at 37°C was monitored by recording the OD₅₉₅. Graphs represent means ± standard deviations of data from 3 independent biological replicates.