Electron donor-dependent radionuclide reduction and nanoparticle formation by Anaeromyxobacter dehalogenans strain 2CP-C
Anaeromyxobacter dehalogenans strain 2CP-C reduces U(VI) and Tc(VII) to U(IV)O2(s) (uraninite) and Tc(IV)O2(S) respectively. Kinetic studies with resting cells revealed that U(VI) or Tc(VII) reduction rates using H2 as electron donor exceeded those observed in acetate-amended incubations. The reduction of U(VI) by A. dehalogenans 2CP-C resulted in extracellular accumulation of ∼5 nm uraninite nanoparticles in association with a lectin-binding extracellular polymeric substance (EPS). The electron donor did not affect UO2(S) nanoparticle size or association with EPS, but the utilization of acetate as the source of reducing equivalents resulted in distinct UO2(S) nanoparticle aggregates that were ∼50 nm in diameter. In contrast, reduction of Tc(VII) by A. dehalogenans 2CP-C cell suspensions produced dense clusters of TcO2 particles, which were localized within the cell periplasm and on the outside of the outer membrane. In addition to direct reduction, A. dehalogenans 2CP-C cell suspensions reduced Tc(VII) indirectly via an Fe(II)-mediated mechanism. Fe(II) produced by strain 2CP-C from either ferrihydrite or Hanford Site sediment rapidly removed 99Tc(VII)O4– from solution. These findings expand our knowledge of the radionuclide reduction processes catalysed by Anaeromyxobacter spp. that may influence the fate and transport of radionuclide contaminants in the subsurface.
Document Type: Research Article
Affiliations: 1: Biological Sciences Division, 2: Environmental Molecular Sciences Laboratory, and 3: School of Civil and Environmental Engineering and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332-0512, USA. 4: Department of Geology, University of Illinois, Urbana, IL 61801-2352, USA. 5: Chemical and Material Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99354, USA.
Publication date: 2009-02-01