title: Characterization of the biochemical-pathway of uranium (VI) reduction in facultative anaerobic bacteria.
abstract: Cultures of U(VI) reducing bacteria sourced from abandoned uranium mine tailing dam were evaluated for their ability to reduce U(VI) to U(IV). The species in the cultures reduced U(VI) in solutions with initial U(VI) concentration up to 400mgL(-)(1) under a near neutral pH of 6.5. The electron flow pathway and fate of reduced species was also analysed in the individual species in order to evaluate the potential for control and optimisation of the reduction potential at the biochemical level. The results showed that U(VI) reduction in live cells was completely blocked by the NADH-dehydrogenase inhibitor, rotenone (C23H22O6), and thioredoxin inhibitor, cadmium chloride (CdCl2), showing that U(VI) reduction involves the electron flow through NADH-dehydrogenase, a primary electron donor to the electron transport respiratory (ETR) system. Mass balance analysis of uranium species aided by visual and electron microscopy suggest that most U(VI) reduction occurred on the cell surface of the isolated species. This finding indicates the possibility of easy uranium recovery for beneficial use through biological remediation. Should the U(VI) be reduced inside the cell, recovery would require complete disruption of the cells and therefore would be difficult. The study contributes new knowledge on the underlying mechanisms in the U(VI) reduction in facultative anaerobes.
authors: Environmental Engineering Group, Department of Chemical Engineering, University of Pretoria, Pretoria 0002, South Africa. Electronic address: mtimunyepj@gmail.com.
authors: Phalazane J
authors: PJ
authors: Mtimunye
authors: Environmental Engineering Group, Department of Chemical Engineering, University of Pretoria, Pretoria 0002, South Africa.
authors: Evans M N
authors: EM
authors: Chirwa
mesh_terms: D001421:Bacteria, Anaerobic / Q000378:metabolism*; D019256:Cadmium Chloride / Q000494:pharmacology; D008854:Microscopy, Electron; D008906:Mining; D010084:Oxidation-Reduction / Q000187:drug effects; D012402:Rotenone / Q000494:pharmacology; D013045:Species Specificity; D014501:Uranium / Q000032:analysis / Q000378:metabolism*; D014866:Waste Products / Q000032:analysis*
chemical_list: D014866:Waste Products; D012402:Rotenone; D014501:Uranium; D019256:Cadmium Chloride
keywords: Electron flow pathway; Facultative anaerobes; U(VI) reduction; Uranium recovery