skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Evidence for multiple modes of uranium immobilization by an anaerobic bacterium

Abstract

Microbial reduction of hexavalent uranium has been studied widely for its potential role in bioremediation and immobilization of soluble U(VI) in contaminated groundwater. More recently, some microorganisms have been examined for their role in immobilization of U(VI) via precipitation of uranyl phosphate minerals mediated by microbial phosphate release, alleviating the requirement for long-term redox control. Here, we investigated the mechanism of U(VI) removal mediated by an environmental isolate, strain UFO1, that is indigenous to the Field Research Center (FRC) in Oak Ridge, TN and has been detected in U(VI)-contaminated sediments. Changes in U(VI) speciation were examined in the presence and absence of the electron-shuttling moiety, anthraquinone-2,6-disulfonate (AQDS). Cell suspensions were capable of nearly complete removal of 100 μM U(VI) from solution within 48 hours; U(VI) removal was not dependent on the presence of an exogenous electron donor or AQDS, although AQDS increased the rate of U(VI) removal. X-ray Absorption Near Edge Structure (XANES) spectroscopic measurements indicated that U(IV) was the predominant oxidation state of uranium in cell suspensions in both the absence and presence of 100 μM AQDS. However, extended X-ray Absorption Fine Structure spectroscopy (EXAFS) measurements indicated that 17% of the cell-associated precipitates in a U(VI)-treated suspension that lackedmore » AQDS had spectral characteristics consistent with a uranyl phosphate solid phase. The potential involvement of phosphate was consistent with observed increases in soluble phosphate concentrations over time in UFO1 cell suspensions, which suggested phosphate liberation from the cells. TEM-EDS confirmed the presence of uranyl phosphate with a U:P ratio consistent with autunite (1:1). EXAFS analyses further showed that U(IV) was present predominantly as a monomeric complex sorbed to carboxylate functional groups on biomass and also suggested that a fraction of the U(IV) was coordinated to phosphoryl ligands. These results suggest that strain UFO1 has the ability to facilitate U(VI) removal from solution via both reductive and phosphate precipitation mechanisms, and may potentially be useful for the remediation of U-contaminated sediments at the FRC or elsewhere.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1023110
Report Number(s):
PNNL-SA-66854
Journal ID: ISSN 0016-7037; 16490; KP1704020; TRN: US1104454
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 75; Journal Issue: 10; Journal ID: ISSN 0016-7037
Publisher:
The Geochemical Society; The Meteoritical Society
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 54 ENVIRONMENTAL SCIENCES; ABSORPTION SPECTROSCOPY; AUTUNITE; BINDING ENERGY; BIOREMEDIATION; CONTAMINATION; FINE STRUCTURE; GROUND WATER; MICROORGANISMS; PHOSPHATES; PRECIPITATION; REMOVAL; SEDIMENTS; SPECTROSCOPY; URANIUM; URANYL PHOSPHATES; VALENCE; Uranium; bacteria; metal reduction; Environmental Molecular Sciences Laboratory

Citation Formats

Ray, Allison E., Bargar, John R., Sivaswamy, Vaideeswaran, Dohnalkova, Alice C., Fujita, Yoshiko, Peyton, Brent M., and Magnuson, Timothy S. Evidence for multiple modes of uranium immobilization by an anaerobic bacterium. United States: N. p., 2011. Web. doi:10.1016/j.gca.2011.02.040.
Ray, Allison E., Bargar, John R., Sivaswamy, Vaideeswaran, Dohnalkova, Alice C., Fujita, Yoshiko, Peyton, Brent M., & Magnuson, Timothy S. Evidence for multiple modes of uranium immobilization by an anaerobic bacterium. United States. doi:10.1016/j.gca.2011.02.040.
Ray, Allison E., Bargar, John R., Sivaswamy, Vaideeswaran, Dohnalkova, Alice C., Fujita, Yoshiko, Peyton, Brent M., and Magnuson, Timothy S. Sun . "Evidence for multiple modes of uranium immobilization by an anaerobic bacterium". United States. doi:10.1016/j.gca.2011.02.040.
@article{osti_1023110,
title = {Evidence for multiple modes of uranium immobilization by an anaerobic bacterium},
author = {Ray, Allison E. and Bargar, John R. and Sivaswamy, Vaideeswaran and Dohnalkova, Alice C. and Fujita, Yoshiko and Peyton, Brent M. and Magnuson, Timothy S.},
abstractNote = {Microbial reduction of hexavalent uranium has been studied widely for its potential role in bioremediation and immobilization of soluble U(VI) in contaminated groundwater. More recently, some microorganisms have been examined for their role in immobilization of U(VI) via precipitation of uranyl phosphate minerals mediated by microbial phosphate release, alleviating the requirement for long-term redox control. Here, we investigated the mechanism of U(VI) removal mediated by an environmental isolate, strain UFO1, that is indigenous to the Field Research Center (FRC) in Oak Ridge, TN and has been detected in U(VI)-contaminated sediments. Changes in U(VI) speciation were examined in the presence and absence of the electron-shuttling moiety, anthraquinone-2,6-disulfonate (AQDS). Cell suspensions were capable of nearly complete removal of 100 μM U(VI) from solution within 48 hours; U(VI) removal was not dependent on the presence of an exogenous electron donor or AQDS, although AQDS increased the rate of U(VI) removal. X-ray Absorption Near Edge Structure (XANES) spectroscopic measurements indicated that U(IV) was the predominant oxidation state of uranium in cell suspensions in both the absence and presence of 100 μM AQDS. However, extended X-ray Absorption Fine Structure spectroscopy (EXAFS) measurements indicated that 17% of the cell-associated precipitates in a U(VI)-treated suspension that lacked AQDS had spectral characteristics consistent with a uranyl phosphate solid phase. The potential involvement of phosphate was consistent with observed increases in soluble phosphate concentrations over time in UFO1 cell suspensions, which suggested phosphate liberation from the cells. TEM-EDS confirmed the presence of uranyl phosphate with a U:P ratio consistent with autunite (1:1). EXAFS analyses further showed that U(IV) was present predominantly as a monomeric complex sorbed to carboxylate functional groups on biomass and also suggested that a fraction of the U(IV) was coordinated to phosphoryl ligands. These results suggest that strain UFO1 has the ability to facilitate U(VI) removal from solution via both reductive and phosphate precipitation mechanisms, and may potentially be useful for the remediation of U-contaminated sediments at the FRC or elsewhere.},
doi = {10.1016/j.gca.2011.02.040},
journal = {Geochimica et Cosmochimica Acta},
issn = {0016-7037},
number = 10,
volume = 75,
place = {United States},
year = {2011},
month = {5}
}