FIG 8.

Deletion of codY in the (p)ppGpp⁰ background restores intracellular metal accumulation, H₂O₂ production, and culture acidification. (A) Intracellular metal quantifications of E. faecalis OG1RF, (p)ppGpp⁰, and (p)ppGpp⁰ ΔcodY strains grown to mid-log phase (OD₆₀₀, ∼0.5) in metal-replete FMC medium. The bar graphs show averages and standard deviations of results from three independent ICP-OES analyses (*, P ≤ 0.05). (B) Quantification of H₂O₂ production in OG1RF, (p)ppGpp⁰, and (p)ppGpp⁰ ΔcodY strains. Cells were grown to an OD₆₀₀ of ∼0.3 in FMC medium depleted of Mn and were harvested by centrifugation. Then, cells were washed twice in NaPO₄ buffer, mixed with Amplex red solution, and incubated for 30 min before H₂O₂ determination. The graphs show averages and standard deviations of results from six independent experiments (*, P ≤ 0.05). (C) For pH determination, cells were grown to late log phase in FMC complete medium and culture pH was immediately recorded.