Uranium Reduction by Desulfovibrio desulfuricans Strain G20 and a Cytochrome c sub(3) Mutant

To determine if cytochrome c sub(3) was essential for hexavalent uranium reduction, a cytochrome c sub(3) mutant of Desulfovibrio desulfuricans strain G20 was assayed for its ability to reduce U(VI) enzymatically. The parent of the mutant was found to reduce U(VI) enzymatically with lactate, pyruvate, or hydrogen as the electron donor, but the mutant lacking the cytochrome reduced U(VI) poorly with hydrogen as the electron donor. The mutant, however, was capable of reducing U(VI) with lactate as the electron donor at about half the rate of the wild type, while the rate was about a third of that by the wild type when pyruvate was the electron donor. This indicated that pathways independent of cytochrome c sub(3) were functioning in U(VI) reduction in D. desulfuricans strain G20.