The effect of pH and natural microbial phosphatase activity on the speciation of uranium in subsurface soils

Beazley, Melanie J.; Martinez, Robert J.; Webb, Samuel M.; Sobecky, Patricia A.; Taillefert, Martial

doi:10.1016/j.gca.2011.07.006

Cited by 67 publications

(43 citation statements)

References 86 publications

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“…Finally, we should note that while the concentrations of U used in this study are within the range of U concentrations found in contaminated sites (up to ϳ0.2 mM) (46), the concentrations of organic phosphates are far above those found at contaminated sites (41). Since U biomineralization and toxicity are dependent on the ratio of U to organic phosphate ( Fig.…”

Section: Discussionmentioning

confidence: 48%

“…XRD analysis showed that the precipitates are in the form of meta-autunite, with no alteration of the U(VI) redox state during the biomineralization process, in contrast to reductive precipitation by DMRB under anaerobic conditions (5,13). Immobilization of U as U(VI) phosphate minerals under aerobic conditions offers the possibility of long-term U stability, since meta-autunite minerals have been shown to be stable for long periods of time, over a wide range of pHs (41). These results thus highlight the potential utility of C. crescentus for U immobilization in the oxic zones of contaminated sites.…”

Section: Discussionmentioning

confidence: 98%

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Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

Yung

Jiao

2014

Appl Environ Microbiol

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Caulobacter crescentus is known to tolerate high levels of uranium [U(VI)], but its detoxification mechanism is poorly understood. Here we show that C. crescentus is able to facilitate U(VI) biomineralization through the formation of U-P i precipitates via its native alkaline phosphatase activity. The U-P i precipitates, deposited on the cell surface in the form of meta-autunite structures, have a lower U/P i ratio than do chemically produced precipitates. The enzyme that is responsible for the phosphatase activity and thus the biomineralization process is identified as PhoY, a periplasmic alkaline phosphatase with broad substrate specificity. Furthermore, PhoY is shown to confer a survival advantage on C. crescentus toward U(VI) under both growth and nongrowth conditions. Results obtained in this study thus highlight U(VI) biomineralization as a resistance mechanism in microbes, which not only improves our understanding of bacterium-mineral interactions but also aids in defining potential ecological niches for metal-resistant bacteria.

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Section: Discussionmentioning

confidence: 48%

Section: Discussionmentioning

confidence: 98%

Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

Yung

Jiao

2014

Appl Environ Microbiol

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“…To measure concentrations in the residual fraction, 5 mL of concentrated HNO 3 was added to the remaining sediment and heated at 85 8C for 3 h, rather than using X-ray fluorescence. [42,55] Sequential U and As extractions were also performed based upon a modified method from Tessier et al [56] as described in Salome et al [42] Extracts were also analysed for both U and As by ICP-MS. Additional elemental measurements of the soil samples were performed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP/MS) at the Environmental Molecular Sciences Laboratory (EMSL), part of the Pacific Northwest National Laboratory (PNNL) in Richland, Washington. The primary purpose of the additional measurements was to independently determine the mineral surface concentration of U and As on unaltered samples.…”

Section: Laboratory Methodsmentioning

confidence: 99%

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Troyer

Stone

2014

Environ. Chem.

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Environmental context. Uranium and arsenic, two elements of human health concern, are commonly found at sites of uranium mining, but little is known about processes influencing their environmental behaviour. Here we focus on understanding the chemical and physical processes controlling uranium and arsenic transport at an abandoned uranium mine. We find that the use of sedimentation ponds limits the mobility of uranium; however, pond conditions at our site resulted in arsenic mobilisation. Our findings will help optimise restoration strategies for mine tailings.Abstract. Although As can occur in U ore at concentrations up to 10 wt-%, the fate and transport of both U and As at U mine tailings have not been previously investigated at a watershed scale. The major objective of this study was to determine primary chemical and physical processes contributing to transport of both U and As to a down gradient watershed at an abandoned U mine site in South Dakota. Uranium is primarily transported by erosion at the site, based on decreasing concentrations in sediment with distance from the tailings. Sequential extractions and U X-ray absorption near-edge fine structure (XANES) fitting indicate that U is immobilised in a near-source sedimentation pond both by prevention of sediment transport and by reduction of U VI to U IV . In contrast to U, subsequent release of As to the watershed takes place from the pond partially due to reductive dissolution of Fe oxy(hydr)oxides. However, As is immobilised by adsorption to clays and Fe oxy(hydr)oxides in oxic zones and by formation of As-sulfide mineral phases in anoxic zones down gradient, indicated by sequential extractions and As XANES fitting. This study indicates that As should be considered during restoration of uranium mine sites in order to prevent transport.

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“…Studies examining phosphatase activities (e.g., alkaline or acid) of genetically engineered and naturally occurring strains of Gram-positive and Gram-negative bacteria were shown to promote U immobilization (>90% precipitation of soluble U) via precipitation and coprecipitation reactions [50,57,60,74,[149][150][151][152][153]. Interestingly, soil bacterial isolates demonstrated constitutive phosphatase activities that liberated comparable, if not greater concentrations, of reactive phosphate when compared to the phosphatase activities of genetically modified strains [57,149].…”

Section: Phosphatase-mediated Biomineralizationmentioning

confidence: 99%

“…Additionally, synchrotron X-ray techniques (e.g., XRD, XANES, and EXAFS) have become tools for biogeochemical studies that enhance our understanding of in situ contaminant sequestration. Recent studies that incorporate X-ray techniques have elucidated U interactions with sediment surfaces and biomass as well as facilitated mineral identification [60,153,179,[207][208][209]. Combining results from such interdisciplinary studies need to be placed in the context of the whole "in terra" system for long-term fieldscale applications [210].…”

Section: Summary Challenges and Future Directionsmentioning

confidence: 99%

Phosphate-Mediated Remediation of Metals and Radionuclides

Martinez

Beazley

Sobecky

2014

Advances in Ecology

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Worldwide industrialization activities create vast amounts of organic and inorganic waste streams that frequently result in significant soil and groundwater contamination. Metals and radionuclides are of particular concern due to their mobility and longterm persistence in aquatic and terrestrial environments. As the global population increases, the demand for safe, contaminantfree soil and groundwater will increase as will the need for effective and inexpensive remediation strategies. Remediation strategies that include physical and chemical methods (i.e., abiotic) or biological activities have been shown to impede the migration of radionuclide and metal contaminants within soil and groundwater. However, abiotic remediation methods are often too costly owing to the quantities and volumes of soils and/or groundwater requiring treatment. The in situ sequestration of metals and radionuclides mediated by biological activities associated with microbial phosphorus metabolism is a promising and less costly addition to our existing remediation methods. This review highlights the current strategies for abiotic and microbial phosphatemediated techniques for uranium and metal remediation.

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The effect of pH and natural microbial phosphatase activity on the speciation of uranium in subsurface soils

Cited by 67 publications

References 86 publications

Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Phosphate-Mediated Remediation of Metals and Radionuclides

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