Fig 5.

Survival against 4 mM H₂O₂ stress in M9 medium containing 30 μM FeSO₄. (A) E. coli strain BW25113 (WT) and the ΔfetA and ΔfetB strains with a control plasmid (pCntl) were grown in minimal medium in the presence (black bars) or absence (gray bars) of 30 μM FeSO₄. The cultures were stressed with 4 mM H₂O₂ at 37°C in M9 minimal medium with 30 μM FeSO₄ for 30 min, and survival rates were determined based on CFU. Data are means ± standard errors of the means (n = 3). (B) The strains with the pF3 overexpression plasmid were treated similarly to the strains described above for panel A. The survival rates of all overexpression strains are statistically indistinguishable. Data are means ± standard errors of the means (n = 3). (C) Final dilution series of assays performed with M9 medium with 30 μM FeSO₄ are shown for the pCntl strains (left) and the overexpression pF3 strains (right). For these assays, 10 μl of diluted culture poststress was spotted onto M9 agar plates and allowed to grow for 24 h. (D) The fold improvement of the different strains harboring the overexpression plasmid pF3 or pCntl was determined for assays in the presence or absence of FeSO₄.