Biotransformation of Uranium Compounds in High Ionic Strength Brine by a Halophilic Bacterium under Denitrifying Conditions

Francis, A.J.; Dodge, Cleveland J.; Gillow, J. B.; Papenguth, Hans W.

doi:10.1021/es991251e

Cited by 62 publications

(30 citation statements)

References 18 publications

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“…So, it can be concluded that maximum lead biosorption by MWS occured at pH 6. Similar results of optimum pH for lead binding by various sorbents have been reported [7,11,22,23].…”

Section: Effect Of Phsupporting

confidence: 85%

Environmentally Benign Urea‐modifed Triticum aestivum Biomass for Lead (II) Elimination from Aqueous Solutions

Farooq¹,

Khan²,

Athar³

et al. 2010

CLEAN Soil Air Water

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Lead is among the three most toxic heavy metal ions (mercury, lead and cadmium). A number of methods are in use for the treatment of lead contaminated waters. The materials used for these are too expensive to be economical for lower concentrations of lead. Raw biological materials have been investigated as alternates. They can be chemically modified or pretreated in an attempt to increase their metal capturing capacities. A new material has been prepared from widely available wheat straw (WS) and urea using microwave radiation and its biosorptive behavior for lead ions has been studied. Modified wheat straw (MWS) was subjected to aqueous lead ions to optimize parameters like pH, contact time, MWS dose and temperature. A known amount of MWS was put in contact with certain concentrations of Pb (II) ions at specified temperatures and pH for certain periods of time. Time of contact, pH, dose and temperature were optimized. The sorption of lead by MWS followed the Langmuir model with a maximum sorption capacity (q max ) of 31.85 mg/g and pseudo second-order kinetics under a specified set of conditions. The changes in the values of free energy (DG8) and enthalpy (DH8) indicated the spontaneous, feasible and endothermic nature of sorption process. MWS has been found to be better biosorbent for lead ions than simple wheat straw and certain other biosorbents. WS and urea are easily available, cost effective, and the modification process is simple. So, MWS appears to be a cost effective material for Pb (II) sorption.

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“…So, it can be concluded that maximum lead biosorption by MWS occured at pH 6. Similar results of optimum pH for lead binding by various sorbents have been reported [7,11,22,23].…”

Section: Effect Of Phsupporting

confidence: 85%

Environmentally Benign Urea‐modifed Triticum aestivum Biomass for Lead (II) Elimination from Aqueous Solutions

Farooq¹,

Khan²,

Athar³

et al. 2010

CLEAN Soil Air Water

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“…However, some Halomonas spp., including H. maura, are capable of anoxic respiration under nitrate reducing conditions (Aragandoña et al 2006;Llamas et al 2006;Peyton et al 2001). Previous studies have utilized Halomonas isolates to study metal-microbe interactions under anoxic conditions (Francis et al 2000;Khijniak et al 2003), although Cr(VI) reduction by a Halomonas isolate has not been reported.…”

Section: Resultsmentioning

confidence: 99%

Fe(III), Cr(VI), and Fe(III) mediated Cr(VI) reduction in alkaline media using a Halomonas isolate from Soap Lake, Washington

et al. 2008

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Hexavalent chromium is one of the most widely distributed environmental contaminants. Given the carcinogenic and mutagenic consequences of Cr(VI) exposure, the release of Cr(VI) into the environment has long been a major concern. While many reports of microbial Cr(VI) reduction are in circulation, very few have demonstrated Cr(VI) reduction under alkaline conditions. Since Cr(VI) exhibits higher mobility in alkaline soils relative to pH neutral soils, and since Cr contamination of alkaline soils is associated with a number of industrial activities, microbial Cr(VI) reduction under alkaline conditions requires attention.Soda lakes are the most stable alkaline environments on earth, and contain a wide diversity of alkaliphilic organisms. In this study, a bacterial isolate belonging to the Halomonas genus was obtained from Soap Lake, a chemically stratified alkaline lake located in central Washington State. The ability of this isolate to reduce Cr(VI) and Fe(III) was assessed under alkaline (pH = 9), anoxic, non-growth conditions with acetate as an electron donor. Metal reduction rates were quantified using Monod kinetics. In addition, Cr(VI) reduction experiments were carried out in the presence of Fe(III) to evaluate the possible enhancement of Cr(VI) reduction rates through electron shuttling mechanisms. While Fe(III) reduction rates were slow compared to previously reported rates, Cr(VI) reduction rates fell within range of previously reported rates.

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“…To simulate a carbonatedominated geochemical condition, a stock solution composed predominantly of uranyl carbonate complexes was prepared by the addition of a 1/10th volume of saturated ammonium carbonate to a 100 mM uranyl nitrate hexahydrate stock solution (final U concentration, 89 mM; carbonate concentration, 214 mM) (32,35,36). The formation of carbonate complexes with U was verified by monitoring the absorption spectra of solution in the visible light range between 400 and 500 nm (UV Unicam 300; Thermo Scientific) with specific peaks at 434 nm, 448 nm, and 464 nm (35,36 ammonium carbonate, as explained above; final pH, 9.0). The concentration of carbonate in GC2 in all assays was always 2.4-fold higher than the U concentration used; i.e., the carbonate-to-U ratio of 2.4 was always maintained.…”

Section: Methodsmentioning

confidence: 99%

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation

Kulkarni

Misra

Gupta

et al. 2016

Appl Environ Microbiol

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Deinococcus radiodurans and Escherichia coli expressing either PhoN, a periplasmic acid phosphatase, or PhoK, an extracellular alkaline phosphatase, were evaluated for uranium (U) bioprecipitation under two specific geochemical conditions (GCs): (i) a carbonate-deficient condition at near-neutral pH (GC1), and (ii) a carbonate-abundant condition at alkaline pH (GC2). Transmission electron microscopy revealed that recombinant cells expressing PhoN/PhoK formed cell-associated uranyl phosphate precipitate under GC1, whereas the same cells displayed extracellular precipitation under GC2. These results implied that the cell-bound or extracellular location of the precipitate was governed by the uranyl species prevalent at that particular GC, rather than the location of phosphatase. MINTEQ modeling predicted the formation of predominantly positively charged uranium hydroxide ions under GC1 and negatively charged uranyl carbonate-hydroxide complexes under GC2. Both microbes adsorbed 6-to 10-fold more U under GC1 than under GC2, suggesting that higher biosorption of U to the bacterial cell surface under GC1 may lead to cell-associated U precipitation. In contrast, at alkaline pH and in the presence of excess carbonate under GC2, poor biosorption of negatively charged uranyl carbonate complexes on the cell surface might have resulted in extracellular precipitation. The toxicity of U observed under GC1 being higher than that under GC2 could also be attributed to the preferential adsorption of U on cell surfaces under GC1. This work provides a vivid description of the interaction of U complexes with bacterial cells. The findings have implications for the toxicity of various U species and for developing biological aqueous effluent waste treatment strategies. IMPORTANCEThe present study provides illustrative insights into the interaction of uranium (U) complexes with recombinant bacterial cells overexpressing phosphatases. This work demonstrates the effects of aqueous speciation of U on the biosorption of U and the localization pattern of uranyl phosphate precipitated as a result of phosphatase action. Transmission electron microscopy revealed that location of uranyl phosphate (cell associated or extracellular) was primarily influenced by aqueous uranyl species present under the given geochemical conditions. The data would be useful for understanding the toxicity of U under different geochemical conditions. Since cell-associated precipitation of metal facilitates easy downstream processing by simple gravitybased settling down of metal-loaded cells, compared to cumbersome separation techniques, the results from this study are of considerable relevance to effluent treatment using such cells. Bioremediation strategies, such as bioreduction (1-3), biosorption (4-8), bioaccumulation (9, 10), and bioprecipitation (5, 11, 12, 13), have been studied for their potential to immobilize U from solutions. There is also a large body of work on microbial interactions with uranium relevant to environmental in situ bioremediation. The...

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Biotransformation of Uranium Compounds in High Ionic Strength Brine by a Halophilic Bacterium under Denitrifying Conditions

Cited by 62 publications

References 18 publications

Environmentally Benign Urea‐modifed Triticum aestivum Biomass for Lead (II) Elimination from Aqueous Solutions

Environmentally Benign Urea‐modifed Triticum aestivum Biomass for Lead (II) Elimination from Aqueous Solutions

Fe(III), Cr(VI), and Fe(III) mediated Cr(VI) reduction in alkaline media using a Halomonas isolate from Soap Lake, Washington

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation

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