In situ uranium stabilization by microbial metabolites

Turick, Charles E.; Knox, Anna Sophia; Leverette, Chad L.; Kritzas, Yianne G.

doi:10.1016/j.jenvrad.2007.11.020

Cited by 38 publications

(32 citation statements)

References 25 publications

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“…The retained U was associated with acid soluble and organic fractions of the wetland sediments, and the U L 3 -edge XANES spectra of the retained U are nearly identical to that of uranyl acetate (U(VI)). These results might indicate that the molecular mechanisms for the high U retention onto the SRS wetland sediments would be either chemical sorption or bonding with NOM-like humate colloids (Wan et al 2011) or accumulation in the wetland plants (Hinton et al, 2005;Knox et al, 2008) that constituted a significant source of the NOM in the SRS wetland sediments. n/a = not available.…”

Section: Discussionmentioning

confidence: 99%

“…long term U immobilization in wetlands include the chemical and/or microbial reduction of soluble U(VI) ions to fairly insoluble U(IV) species (Kalin et al, 2005;Lovley et al, 1991;Noubactep et al, 2006;Turick et al, 2008), mineral precipitation, sorption onto NOM (Wan et al, 2011), ion exchange or sorption to sediment minerals (Akber et al, 1992;Dong et al, 2012;Grybos et al, 2007), and accumulation in plants (Hinton et al, 2005;Knox et al, 2008).…”

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confidence: 99%

“…Bertsch et al (1994) reported the in situ characterization of chemical speciation of U in the sand fraction of a SRS sediment sample using micro X-ray absorption spectroscopy, which appeared to indicate the presence of U(VI). Given these initial observation that much of the U may naturally exist in the U(VI) form, the remediation technologies of the contaminated SRS sediments with apatite (Ca 10 (PO 4 ) 6 (OH, F) 2 ) (Arey et al, 1999;Kaplan et al, 2004;Seaman et al, 2001), humic acid (Wan et al, 2011), native trees (Hinton et al, 2005, natural hyperaccumulators, for example, the netted chain fern (Woodwardia areolata) (Knox et al, 2007), and microbial metabolites (Turick et al, 2008) have been evaluated. However, the tendency of U to enter the mobile phase and become available to local biota or be transported from the contaminated area has not been well quantified.…”

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confidence: 99%

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Retention and chemical speciation of uranium in an oxidized wetland sediment from the Savannah River Site

Seaman

Chang

et al. 2014

Journal of Environmental Radioactivity

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Uranium speciation and retention mechanism onto Savannah River Site (SRS) wetland sediments was studied using batch (ad)sorption experiments, sequential extraction desorption 2 tests and U L 3 -edge X-ray absorption near-edge structure (XANES) spectroscopy of contaminated wetland sediments. U was highly retained by the SRS wetland sediments. In contrast to other similar but much lower natural organic matter (NOM) sediments, significant sorption of U onto the SRS sediments was observed at pH <4 and pH >8. Sequential extraction tests indicated that the U(VI) species were primarily associated with the acid soluble fraction (weak acetic acid extractable) and NOM fraction (Na-pyrophosphate extractable). Uranium L 3 -edge XANES spectra of the U-retained sediments were nearly identical to that of uranyl acetate.The primary oxidation state of U in these sediments was as U(VI), and there was little evidence that the high sorptive capacity of the sediments could be ascribed to abiotic or biotic reduction to the less soluble U(IV) species. The molecular mechanism responsible for the high U retention in the SRS wetland sediments is likely related to the chemical bonding of U to organic carbon.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Retention and chemical speciation of uranium in an oxidized wetland sediment from the Savannah River Site

Seaman

Chang

et al. 2014

Journal of Environmental Radioactivity

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“…Chemical and physical techniques for waste treatment or removal of U are challenging and expensive. An alternative method for U remediation is microbially mediated, in situ U immobilization, which has added benefits of reduced cost and environmental friendliness relative to other approaches (3,4).…”

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confidence: 99%

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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“…Thus, the amount of iron assimilated by the bacterium may not be solely dependent on the concentration of the Fe 2ϩ generated but may be influenced by the polymerized status of the reducing agent or the nature of a HGA-melanin complex. Other pyomelanins present in the soil have been linked to the sequestration of other metals, including uranium, molybdenum, lead, bismuth, and arsenic (54). In thinking about the ferric iron reduction reaction itself, it is possible that HGA and HGA-melanin do not always act alone; e.g., a secreted protease of L. pneumophila that degrades transferrin (55) may improve the access of HGA to the ferric iron in that host iron chelate.…”

Section: Figmentioning

confidence: 99%

Secreted Pyomelanin of Legionella pneumophila Promotes Bacterial Iron Uptake and Growth under Iron-Limiting Conditions

et al. 2013

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Iron acquisition is critical to the growth and virulence of Legionella pneumophila. Previously, we found that L. pneumophila uses both a ferrisiderophore pathway and ferrous iron transport to obtain iron. We now report that two molecules secreted by L. pneumophila, homogentisic acid (HGA) and its polymerized variant (HGA-melanin, a pyomelanin), are able to directly mediate the reduction of various ferric iron salts. Furthermore, HGA, synthetic HGA-melanin, and HGA-melanin derived from bacterial supernatants enhanced the ability of L. pneumophila and other species of Legionella to take up radiolabeled iron. Enhanced iron uptake was not observed with a ferrous iron transport mutant. Thus, HGA and HGA-melanin mediate ferric iron reduction, with the resulting ferrous iron being available to the bacterium for uptake. Upon further testing of L. pneumophila culture supernatants, we found that significant amounts of ferric and ferrous iron were associated with secreted HGA-melanin. Importantly, a pyomelanin-containing fraction obtained from a wild-type culture supernatant was able to stimulate the growth of iron-starved legionellae. That the corresponding supernatant fraction obtained from a nonpigmented mutant culture did not stimulate growth demonstrated that HGA-melanin is able to both promote iron uptake and enhance growth under iron-limiting conditions. Indicative of a complementary role in iron acquisition, HGA-melanin levels were inversely related to the levels of siderophore activity. Compatible with a role in the ecology and pathogenesis of L. pneumophila, HGA and HGA-melanin were effective at reducing and releasing iron from both insoluble ferric hydroxide and the mammalian iron chelates ferritin and transferrin.

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In situ uranium stabilization by microbial metabolites

Cited by 38 publications

References 25 publications

Retention and chemical speciation of uranium in an oxidized wetland sediment from the Savannah River Site

Retention and chemical speciation of uranium in an oxidized wetland sediment from the Savannah River Site

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

Secreted Pyomelanin of Legionella pneumophila Promotes Bacterial Iron Uptake and Growth under Iron-Limiting Conditions

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