U biomineralization by subsurface microbes
Mardi 25 mars 2014 11:00
- Duree : 1 heure
Lieu : C5-421, CEA - 17 rue des Martyrs - Grenoble
Orateur : Professeur Rizlan BERNIER-LATMANI (Ecole Polytechnique Fédérale de Lausanne, Suisse)
Microorganisms are capable of transforming soluble and mobile hexavalent uranium [U(VI)] to sparingly soluble and relatively immobile tetravalent uranium [U(IV)] through the transfer of two electrons or one electron followed by disproportionation. This process can be carried out directly, enzymatically, by the microorganisms or indirectly, through the reduction of iron or sulfate. Uranium reduction by microbes is relevant for the bioremediation of the subsurface contaminated with hexavalent uranium, for the formation of uranium ore roll front deposits and for the mobility of uranium in radioactive waste geological repositories. Using X-ray Absorption Spectroscopy, we investigate the product(s) of microbial uranium reduction and find that while crystalline nanoparticulate uraninite (UO2) is a product of the reduction process, another product, an amorphous, phosphate-coordinated U(IV) species is more predominant in many environments. Another synchrotron technique, Scanning Transmission X-ray Microscopy, enabled the identification of microbial biofilms as the controlling factor for the formation of this non-crystalline species referred to as non-uraninite U(IV). These results taken together suggest the importance of indirect biological processes in the reduction of uranium in subsurface environments. Further studies utilizing the fractionation of uranium isotopes as a result of reduction are underway.
Contact : zohra.termache@cea.fr
Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (INAC/SCIB)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire SCIB)
Site de l'évènement : Site CEA avec accès badge
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