FIG. 6.

Comparison of H₂ (A and C) to electrical reducing power (2eV) (B and D) as an electron donor for reduction of fumarate to succinate by purified membranes (A and B) and solubilized membranes (C and D) from A. succinogenes. Membranes (3.25 mg of protein/ml) and solubilized membranes (3.2 mg of protein/ml) were suspended in 50 mM KPO₄ buffer (pH 7.2), and where indicated, 50 μM NR and 1 mM NAD were added. Symbols: ●, N₂ control; ■, H₂ alone; ▴, H₂ + NAD⁺; ▾, H₂ + NR; ⧫, H₂ + NAD⁺ + NR; ○, control 2eV alone; □, 2eV + NR; ▵, 2eV + NAD⁺; ▿, 2eV + NAD⁺ + NR.