title: Kinetics of microbial reduction of Solid phase U(VI).
abstract: Sodium boltwoodite (NaUO2SiO3OH x 1.5 H2O) was used to assess the kinetics of microbial reduction of solid-phase U(VI) by a dissimilatory metal-reducing bacterium (DMRB), Shewanella oneidensis strain MR-1. The bioreduction kinetics was studied with Na-boltwoodite in suspension or within alginate beads in a nongrowth medium with lactate as electron donor at pH 6.8 buffered with PIPES. Concentrations of U(VI)tot and cell number were varied to evaluate the coupling of U(VI) dissolution, diffusion, and microbial activity. Microscopic and spectroscopic analyses with transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and laser-induced fluorescence spectroscopy (LIFS) collectively indicated that solid-phase U(VI) was first dissolved and diffused out of grain interiors before it was reduced on bacterial surfaces and/or within the periplasm. The kinetics of solid-phase U(VI) bioreduction was well described by a coupled model of bicarbonate-promoted dissolution of Na-boltwoodite, intragrain uranyl diffusion, and Monod type bioreduction kinetics with respect to dissolved U(VI) concentration. The results demonstrated that microbial reduction of solid-phase U(VI) is controlled by coupled biological, chemical, and physical processes.
authors.affiliation: Pacific Northwest National Laboratory, Richland, Washington 99352, USA. Chongxuan.liu@pnl.gov
authors.forename: Chongxuan
authors.initials: C
authors.lastname: Liu
authors.forename: Byong-Hun
authors.initials: BH
authors.lastname: Jeon
authors.forename: John M
authors.initials: JM
authors.lastname: Zachara
authors.forename: Zheming
authors.initials: Z
authors.lastname: Wang
authors.forename: Alice
authors.initials: A
authors.lastname: Dohnalkova
authors.forename: James K
authors.initials: JK
authors.lastname: Fredrickson
mesh_terms: D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction; D019897:Periplasm / Q000378:metabolism / Q000648:ultrastructure; D020592:Shewanella / Q000378:metabolism* / Q000648:ultrastructure; D013050:Spectrometry, Fluorescence; D014501:Uranium / Q000378:metabolism*; D017974:Uranium Compounds / Q000378:metabolism*
chemical_list: D017974:Uranium Compounds; D014501:Uranium