Can microbially-generated hydrogen sulfide account for the rates of U(VI) reduction by a sulfate-reducing bacterium?

Boonchayaanant, Benjaporn; Gu, Baohua; Wang, Wei; Ortiz, Monica E.; Criddle, Craig S.

doi:10.1007/s10532-009-9283-x

Cited by 27 publications

(22 citation statements)

References 40 publications

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“…However, the growth medium in all cases contained trace amounts of ferrous iron, and it was shown previously that the presence of a trace amount of ferrous iron in a 5 mM bicarbonate solution enhances U reduction by hydrogen sulfide. 35 This suggests that hydrogen sulfide is an important and active U reducing agent in mixed and abiotic systems (when amended with 5 mM bicarbonate) and explains the similar level of U immobilization in the +Fe and no-Fe system (Figures 1 and S2).…”

Section: Metabolism and Biofilm Establishment Of D Vulgaris The Resmentioning

confidence: 80%

Mechanism of Uranium Reduction and Immobilization in Desulfovibrio vulgaris Biofilms

Stylo

Neubert

Roebbert

et al. 2015

Environ. Sci. Technol.

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The prevalent formation of noncrystalline U(IV) species in the subsurface and their enhanced susceptibility to reoxidation and remobilization, as compared to crystalline uraninite, raise concerns about the long-term sustainability of the bioremediation of U-contaminated sites. The main goal of this study was to resolve the remaining uncertainty concerning the formation mechanism of noncrystalline U(IV) in the environment. Controlled laboratory biofilm systems (biotic, abiotic, and mixed biotic−abiotic) were probed using a combination of U isotope fractionation and X-ray absorption spectroscopy (XAS). Regardless of the mechanism of U reduction, the presence of a biofilm resulted in the formation of noncrystalline U(IV). Our results also show that biotic U reduction is the most effective way to immobilize and reduce U. However, the mixed biotic−abiotic system resembled more closely an abiotic system: (i) the U(IV) solid phase lacked a typically biotic isotope signature and (ii) elemental sulfur was detected, which indicates the oxidation of sulfide coupled to U(VI) reduction. The predominance of abiotic U reduction in our systems is due to the lack of available aqueous U(VI) species for direct enzymatic reduction. In contrast, in cases where bicarbonate is present at a higher concentration, aqueous U(VI) species dominate, allowing biotic U reduction to outcompete the abiotic processes.

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Section: Metabolism and Biofilm Establishment Of D Vulgaris The Resmentioning

confidence: 80%

Mechanism of Uranium Reduction and Immobilization in Desulfovibrio vulgaris Biofilms

Stylo

Neubert

Roebbert

et al. 2015

Environ. Sci. Technol.

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“…The onset of sulfate reduction does not correspond to elevated rates of U(VI) removal, as does the onset of iron reduction. Although the lowest levels of U(VI) were observed at times when dissolved sulfide concentrations were at a maximum, laboratory experiments investigating the kinetics of U(VI) reduction by aqueous sulfide (Hua et al 2006;Boonchayaanant et al 2010) suggest that the mechanism is suppressed at the pH (∼7.5) and alkalinity levels (15-20 mM; [CO 2− 3 ] T ) observed during this phase of Big Rusty. At lower bicarbonate concentrations (≤5 mM), abiotic reduction of U(VI) by aqueous sulfide has been demonstrated, although neither laboratory study investigated the potentially stabilizing effect of dissolved calcium and the formation of Ca-UO 2 -CO 3 ternary complexes.…”

Section: Post-amendment Uranium Dynamics and Alternate U(vi) Removal mentioning

confidence: 99%

Acetate Availability and its Influence on Sustainable Bioremediation of Uranium-Contaminated Groundwater

Williams

Long

Davis

et al. 2011

Geomicrobiology Journal

227

365

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Field biostimulation experiments at the U.S. Department of Energy's Integrated Field Research Challenge (IFRC) site in Rifle, Colorado, have demonstrated that uranium concentrations in groundwater can be decreased to levels below the U.S. Environmental Protection Agency's (EPA) drinking water standard (0.126 µM).During successive summer experiments -referred to as "Winchester" (2007) and "Big Rusty" (2008) -acetate was added to the aquifer to stimulate the activity of indigenous dissimilatory metalreducing bacteria capable of reductively immobilizing uranium. The two experiments differed in the length of injection (31 vs. 110 days), the maximum concentration of acetate (5 vs. 30 mM), and the extent to which iron reduction ("Winchester") or sulfate reduction ("Big Rusty") was the predominant metabolic process. In both cases, rapid removal of U(VI) from groundwater occurred at calcium concentrations (6 mM) and carbonate alkalinities (8 meq/L) where Ca-UO 2 -CO 3 ternary complexes constitute >90% of uranyl species in groundwater. Complete consumption of acetate and increased alkalinity (>30 meq/L) accompanying the onset of sulfate reduction corresponded to temporary increases in U(VI); however, by increasing acetate concentrations in excess of available sulfate (10 mM), low U(VI) concentrations (0.1-0.05 µM) were achieved for extended periods of time (>140 days). Uniform delivery of acetate during "Big Rusty" was impeded due to decreases in injection well permeability, likely resulting from biomass accumulation and carbonate and sulfide mineral precipitation. Such decreases were not observed during the short-duration "Winchester" experiment. Terminal restriction fragment length polymorphism (TRFLP) analysis of 16S rRNA genes demonstrated that Geobacter sp. and Geobacter-like strains dominated the groundwater community profile during iron reduction, with 13 C stable isotope probing (SIP) results confirming these strains were actively utilizing acetate to replicate their genome during the period of optimal U(VI) removal. Gene transcript levels during "Big Rusty" were quantified for Geobacter-specific citrate synthase (gltA), with ongoing transcription during sulfate reduction indicating that members of the Geobacteraceae were still active and likely contributing to U(VI) removal. The persistence of reducible Fe(III) in sediments recovered from an area of prolonged (110-day) sulfate reduction is consistent with this conclusion. These results indicate that acetate availability and its ability to sustain the activity of iron-and uranyl-respiring Geobacter strains during sulfate reduction exerts a primary control on optimized U(VI) removal from groundwater at the Rifle IFRC site over extended time scales (>50 days).

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“…It was also found that when the medium was buffered with 30 mM carbonate, sulfide did not reduce U(VI) [18]. Recently, other research groups have shown that microbially generated sulfide can reduce uranium in a medium with 15 mM carbonate buffer, and that the lower the carbonate buffer strength, the higher the uranium reduction rate [110].…”

Section: Srb Biofilms On Quartz Surfacementioning

confidence: 98%

Immobilization of Uranium in Groundwater Using Biofilms

Cao

Ahmed

Beyenal

2009

Emerging Environmental Technologies, Volume II

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Uranium is one of the most common radionuclides in soils, sediments, and groundwater at radionuclides-contaminated sites. At these contaminated sites, uranium leaches into the groundwater, which has become a widespread problem at mining and milling sites across North America, South America, and Eastern Europe. The movement of groundwater usually transports soluble uranium contaminants beyond their original boundaries, causing a global problem in aquifers, water supplies, and related ecosystems and posing a serious threat to human health and the natural environment. In order to meet the EPA standards, extensive efforts have been made to assess and remediate uranium-contaminated sites. As a cost-effective technology with minimal disruption to the environment, bioremediation harnessing indigenous microbial processes for cleanup has been utilized for uranium remediation. In the first part of this chapter, various uranium remediation technologies are discussed. Emphasis is placed on the principles and mechanisms of uranium bioremediation and the key factors affecting it. The second part of this chapter focuses on the use of biofilms for uranium immobilization in groundwater from subsurface environments. Most of the literature studies on uranium bioremediation have been conducted with suspended microorganisms or enriched sediments, which were eventually spiked with micro-or nano-particles of other minerals. However, biofilms are the commonly found microbial growth pattern in natural soils and water-sediment interfaces. With heterogeneous and complex biotic, abiotic and redox conditions significantly different from those in bulk conditions, biofilms pose challenges in predicting the mobility of uranium. Although previous studies have improved our understanding of uranium immobilization processes in biofilms, in order to efficiently and sustainably immobilize uranium at contaminated sites using indigenous biofilms, more knowledge is needed on the complex interactions among uranium, biofilms, and various redox-sensitive minerals during in situ uranium bioremediation.

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Can microbially-generated hydrogen sulfide account for the rates of U(VI) reduction by a sulfate-reducing bacterium?

Cited by 27 publications

References 40 publications

Mechanism of Uranium Reduction and Immobilization in Desulfovibrio vulgaris Biofilms

Mechanism of Uranium Reduction and Immobilization in Desulfovibrio vulgaris Biofilms

Acetate Availability and its Influence on Sustainable Bioremediation of Uranium-Contaminated Groundwater

Immobilization of Uranium in Groundwater Using Biofilms

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