TY - JOUR
T1 - Evidence for multiple modes of uranium immobilization by an anaerobic bacterium
AU - Ray, Allison E.
AU - Bargar, John R.
AU - Sivaswamy, Vaideeswaran
AU - Dohnalkova, Alice C.
AU - Fujita, Yoshiko
AU - Peyton, Brent M.
AU - Magnuson, Timothy S.
N1 - Funding Information:
This work was supported by the Idaho National Laboratory (INL) and Inland Northwest Research Alliance (INRA) ; AER was supported by an INRA Subsurface Science Graduate Fellowship , and an INL Graduate Scholarship . Peyton and Sivaswamy were supported by the DOE Environmental Remediation Sciences Program . Support from the Stanford Synchrotron Radiation Lightsource, a national scientific user facility supported by the Department of Energy’s Offices of Basic Energy Sciences and Biological and Environmental Research, provided significant contributions to this research. We thank Chris Fuller (US Geological Survey) for providing the spectrum of autunite and David Clark (Los Alamos National Laboratory) for providing the sample of UO 2.00 . A portion of the research was also performed using EMSL, a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We also thank George Redden for reviewing this manuscript and providing helpful comments. We thank Susan Glasauer and three anonymous reviewers for their help in improving the manuscript.
PY - 2011/5/15
Y1 - 2011/5/15
N2 - 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 100μM U(VI) from solution within 48. h; 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) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopic measurements indicated that U(IV) was the predominant oxidation state of uranium in cell suspensions in both the absence and presence of 100μM AQDS. Interestingly, 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 suggested that U(IV) was bound to low-Z neighbors such as C or P, inferred to be present as functional groups on biomass. These results suggest that strain UFO1 has the ability to facilitate U(VI) removal from solution via reductive and phosphate precipitation mechanisms. Both mechanisms offer potential for the remediation of U-contaminated sediments at the FRC or elsewhere.
AB - 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 100μM U(VI) from solution within 48. h; 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) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopic measurements indicated that U(IV) was the predominant oxidation state of uranium in cell suspensions in both the absence and presence of 100μM AQDS. Interestingly, 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 suggested that U(IV) was bound to low-Z neighbors such as C or P, inferred to be present as functional groups on biomass. These results suggest that strain UFO1 has the ability to facilitate U(VI) removal from solution via reductive and phosphate precipitation mechanisms. Both mechanisms offer potential for the remediation of U-contaminated sediments at the FRC or elsewhere.
UR - http://www.scopus.com/inward/record.url?scp=79955094711&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2011.02.040
DO - 10.1016/j.gca.2011.02.040
M3 - Article
AN - SCOPUS:79955094711
SN - 0016-7037
VL - 75
SP - 2684
EP - 2695
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 10
ER -