Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344T

Stephan Hilpmann; André Rossberg; Robin Steudtner; Björn Drobot; René Hübner; Frank Bok; Damien Prieur; Stephen Bauters; Kristina O Kvashnina; Thorsten Stumpf; Andrea Cherkouk

doi:10.1016/j.scitotenv.2023.162593

Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344^T

Sci Total Environ. 2023 Jun 1:875:162593. doi: 10.1016/j.scitotenv.2023.162593. Epub 2023 Mar 6.

Affiliations

¹ Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany.
² Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany; Rossendorf Beamline (BM20-ROBL), European Synchrotron Radiation Facility, Grenoble, France.
³ Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Dresden, Germany.
⁴ Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany. Electronic address: a.cherkouk@hzdr.de.

PMID: 36889400
DOI: 10.1016/j.scitotenv.2023.162593

Abstract

Microbial U(VI) reduction influences uranium mobility in contaminated subsurface environments and can affect the disposal of high-level radioactive waste by transforming the water-soluble U(VI) to less mobile U(IV). The reduction of U(VI) by the sulfate-reducing bacterium Desulfosporosinus hippei DSM 8344^T, a close phylogenetic relative to naturally occurring microorganism present in clay rock and bentonite, was investigated. D. hippei DSM 8344^T showed a relatively fast removal of uranium from the supernatants in artificial Opalinus Clay pore water, but no removal in 30 mM bicarbonate solution. Combined speciation calculations and luminescence spectroscopic investigations showed the dependence of U(VI) reduction on the initial U(VI) species. Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy showed uranium-containing aggregates on the cell surface and some membrane vesicles. By combining different spectroscopic techniques, including UV/Vis spectroscopy, as well as uranium M₄-edge X-ray absorption near-edge structure recorded in high-energy-resolution fluorescence-detection mode and extended X-ray absorption fine structure analysis, the partial reduction of U(VI) could be verified, whereby the formed U(IV) product has an unknown structure. Furthermore, the U M₄ HERFD-XANES showed the presence of U(V) during the process. These findings offer new insights into U(VI) reduction by sulfate-reducing bacteria and contribute to a comprehensive safety concept for a repository for high-level radioactive waste.

Keywords: Membrane vesicles; Opalinus clay pore water; Pentavalent uranium; Sulfate-reducing bacteria; Uranium(VI) reduction.