FIG 5.

AdhR and SigL maintain cellular redox homeostasis. (A) Effect of formate supplementation on intracellular NADH/NAD⁺ concentration ratio in C. beijerinckii wild type and adhR and sigL mutants. NADH and NAD⁺ concentrations were determined at an OD₆₀₀ of ∼2.0. (B) Effect of exposure to O₂ on intracellular NADH/NAD⁺ concentration ratio in wild type and adhR and sigL mutants. Cells were exposed to O₂ for 30 min. NADH and NAD⁺ concentrations were determined at an OD₆₀₀ of ∼1.0. (C) Effect of formate supplementation on cell growth rate of wild type and adhR and sigL mutants during late-exponential growth phase. (D) Survival of wild type and adhR and sigL mutants after exposure to O₂. The number of surviving cells was normalized to the value for the non-stressed wild type (time zero). Data shown in all figures are means ± the SD (n = 3 independent experiments). Statistical analysis was performed with the unpaired two-tailed Student t test (*, P < 0.05; **, P < 0.01; ***, P < 0.001).