title: Structure of biogenic uraninite produced by Shewanella oneidensis strain MR-1.
abstract: The stability of biogenic uraninite with respect to oxidation is seminal to the success of in situ bioreduction strategies for remediation of subsurface U(VI) contamination. The properties and hence stability of uraninite are dependent on its size, structure, and composition. In this study, the local-, intermediate-, and long-range molecular-scale structure of nanoscale uraninite produced by Shewanella oneidensis strain MR-1 was investigated using EXAFS, SR-based powder diffraction and TEM. The uraninite products were found to be structurally homologous with stoichiometric U02 under all conditions considered. Significantly, there was no evidence for lattice strain of the biogenic uraninite nanoparticles. The fresh nanoparticles were found to exhibit a well-ordered interior core of diameter ca. 1.3 nm and an outer region of thickness ca approximately 0.6 nm in which the structure is locally distorted. The lack of nanoparticle strain and structural homology with stoichiometric U02 suggests that established thermodynamic parameters for the latter material are an appropriate starting point to model the behavior of nanobiogenic uraninite. The detailed structural analysis in this study provides an essential foundation for subsequent investigations of environmental samples.
authors.affiliation: Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025, USA. eleanors@slac.stanford.edu
authors.forename: Eleanor J
authors.initials: EJ
authors.lastname: Schofield
authors.forename: Harish
authors.initials: H
authors.lastname: Veeramani
authors.forename: Jonathan O
authors.initials: JO
authors.lastname: Sharp
authors.forename: Elena
authors.initials: E
authors.lastname: Suvorova
authors.forename: Rizlan
authors.initials: R
authors.lastname: Bernier-Latmani
authors.forename: Apurva
authors.initials: A
authors.lastname: Mehta
authors.forename: Jonathan
authors.initials: J
authors.lastname: Stahlman
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Webb
authors.forename: David L
authors.initials: DL
authors.lastname: Clark
authors.forename: Steven D
authors.initials: SD
authors.lastname: Conradson
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Ilton
authors.forename: John R
authors.initials: JR
authors.lastname: Bargar
mesh_terms: D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D020592:Shewanella / Q000378:metabolism*; D013057:Spectrum Analysis; D013499:Surface Properties; D017356:Synchrotrons; D017974:Uranium Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D017974:Uranium Compounds; C012597:uranium dioxide