title: The U(VI) speciation influenced by a novel Paenibacillus isolate from Mont Terri Opalinus clay.
abstract: Bacterial cell walls have a high density of ionizable functional groups available for U(VI) binding, hence have a great potential to affect the speciation of this contaminant in the environment. The studied strain of the genus Paenibacillus is a novel isolate originating from the Mont Terri Opalinus clay formations (Switzerland) which are currently investigated as a potential host rock for future nuclear waste storage. U(VI) binding to the cell surface functional groups was studied by potentiometry combined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). Four bacterial U(VI) surface complexes were identified: R-COO-UO2(+), R-O-PO3-UO2, R-O-PO3H-UO2(+), and (R-O-PO3)2-UO2(2-). The corresponding complex stability constants were calculated to be 5.33 ± 0.08, 8.89 ± 0.04, 12.92 ± 0.05, and 13.62 ± 0.08, respectively. Hence UO2(2+) displays a moderate to strong interaction with the bacterial surface functional groups. In the acidic pH range (pH 3) UO2(2+) binding onto the cell envelope is governed by coordination to hydrogen phosphoryl sites. Upon increasing the pH an increasing coordination of UO2(2+) to carboxylic and deprotonated phosphoryl sites was found. At a pH greater than 7 uranyl hydroxides dominate the speciation. Additionally the bacteria-mediated release of inorganic phosphate in dependence on [U(VI)] at different pH values was studied to assess the influence of phosphate release on U(VI) mobilization.
authors.affiliation: Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf e.V., P.O. Box 510119, D-01314, Dresden, Germany. l.luetke@hzdr.de
authors.forename: Laura
authors.initials: L
authors.lastname: Lütke
authors.forename: Henry
authors.initials: H
authors.lastname: Moll
authors.forename: Velina
authors.initials: V
authors.lastname: Bachvarova
authors.forename: Sonja
authors.initials: S
authors.lastname: Selenska-Pobell
authors.forename: Gert
authors.initials: G
authors.lastname: Bernhard
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D056831:Coordination Complexes / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D056507:Paenibacillus / Q000302:isolation & purification / Q000378:metabolism*; D011199:Potentiometry; D011850:Radioactive Waste; D012988:Soil Microbiology; D013050:Spectrometry, Fluorescence; D014501:Uranium / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000538:Aluminum Silicates; D056831:Coordination Complexes; D011850:Radioactive Waste; D014501:Uranium; D000077215:Clay