Final Technical Report

Judy D. Wall

关键词: BINDING ENERGY;    BIOREMEDIATION;    CYTOCHROMES;    DESULFOVIBRIO;    ELECTRONS;    GENES;    GENETICS;    HEME;    KINETICS;    LACTATES;    MICROORGANISMS;    MOLYBDATES;    MUTANTS;    MUTATIONS;    OXIDATION;    PROTEINS;    RADIOISOTOPES;    SODIUM;    SOILS;    STRAINS;    SUBSTRATES;    SULFATE-REDUCING BACTERIA;    SULFATES;    VALENCE Bioremediation;    Uranium reduction;    sulfate-reducing bacteria;    c-type cytochromes;    bacterial mutants;   

DOI  :  10.2172/948467
RP-ID  :  DOE/ER/62495-Final
PID  :  OSTI ID: 948467
Others  :  TRN: US1000942

美国|英语

来源: SciTech Connect

【 摘 要 】

Bioremediation of radionuclides and metals in the subsurface necessitate an understanding of the metabolic capacities and interactions of the anaerobic microorganisms that are found there, including members of the sulfate-reducing bacteria (SRB). Genetic investigation into the pathway of reductant flow to U(VI) in the SRB belonging to the genus Desulfovibrio has been the focus of this project. In Dv. desulfuricans strain G20, we confirmed the importance of the tetraheme cytochrome c3 by disruption of the gene encoding that cytochrome, cycA, and demonstrated a decrease in the ability of the mutant (I2) to reduce U(VI). We found that the cytochrome c3 was necessary for electrons from pyruvate to reach sulfate or fumarate as terminal electron acceptors. It was not needed for electrons from lactate to reach sulfate, from which we infer that a different pathway is used for the electrons from these two substrates. Cyrstal structure of the tetraheme cytochrome c3 was obtained and site-directed mutations of the protein indicated a binding site for metals at heme 4 of the structure. Kinetic studies for oxidation of reduced cytochrome c3 with U(VI) or molybdate revealed a preference for U(VI) as a substrate. Evidence for a role for sodium gradients in the energetic scheme for this soil organism was obtained.