Laser Spectroscopic Studies of Interactions of U<sup>VI</sup> with Bacterial Phosphate Species

Knopp, R.; Panak, Petra J.; Wray, L. Andrew; Renninger, Neil S.; Keasling, Jay D.; Nitsche, H.

doi:10.1002/chem.200304711

Cited by 27 publications

(21 citation statements)

References 47 publications

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“…TABLE 5. EXAFS fit results for C, P, and U-O-P multiple-scattering shells and U-O dist SS shells from fits to residual spectra (model B) spectroscopy (37), Raman spectroscopy (27), and time-resolved laser-induced fluorescence spectroscopy (27,37,44). In addition, synchrotron-based techniques such as X-ray absorption spectroscopy have been used to determine the oxidation state (XANES) and to identify the number of atoms and their distances in the local structural environment (EXAFS) of U within a variety of microbial samples (22,26,(38)(39)(40)(41).…”

Section: Discussionmentioning

confidence: 99%

Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12

Merroun

Raff

Roßberg

et al. 2005

Appl Environ Microbiol

243

178

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Bacillus sphaericus JG-A12 is a natural isolate recovered from a uranium mining waste pile near the town of Johanngeorgenstadt in Saxony, Germany. The cells of this strain are enveloped by a highly ordered crystalline proteinaceous surface layer (S-layer) possessing an ability to bind uranium and other heavy metals. Purified and recrystallized S-layer proteins were shown to be phosphorylated by phosphoprotein-specific staining, inductive coupled plasma mass spectrometry analysis, and a colorimetric method. We used extended X-ray absorption fine-structure (EXAFS) spectroscopy to determine the structural parameters of the uranium complexes formed by purified and recrystallized S-layer sheets of B. sphaericus JG-A12. In addition, we investigated the complexation of uranium by the vegetative bacterial cells. The EXAFS analysis demonstrated that in all samples studied, the U(VI) is coordinated to carboxyl groups in a bidentate fashion with an average distance between the U atom and the C atom of 2.88 ؎ 0.02 Å and to phosphate groups in a monodentate fashion with an average distance between the U atom and the P atom of 3.62 ؎ 0.02 Å. Transmission electron microscopy showed that the uranium accumulated by the cells of this strain is located in dense deposits at the cell surface.Uranium is a long-lived radionuclide that is an ecological and human health hazard. The mining and processing of uranium for nuclear power plants and nuclear weapons production have resulted in the generation of significant amounts of radioactive wastes. The mobility of this radionuclide is controlled by its interaction with ions, minerals, and microorganisms present in nature. As a consequence of their small size and diverse metabolic activities, bacteria are able to interact intimately with metal ions present in their environment (15). Highly reactive bacterial cell surfaces bind uranium and other metal ions (7). This reactivity arises from the presence of a wide array of ionizable groups, such as carboxylate and phosphate, present in the lipopolysaccharides (LPS) of gram-negative bacterial cell walls (8) and the peptidoglycan, teichuronic acids, and teichoic acids of gram-positive bacteria (9).The bacterial cell wall may be overlayed by a number of surface structures, which can also interact with metal ions. These may be composed primarily of carbohydrate polymers (e.g., capsules) or proteinaceous surface layers (e.g., S-layers) and may occur singly or in combination (15). The crystalline bacterial cell S-layers represent the outermost cell envelope component of many bacteria and archaea (50). S-layers are generally composed of identical protein or glycoprotein subunits, and they completely cover the cell surface during all stages of bacterial growth and division. Most S-layers are 5 to 15 nm thick and possess pores of identical size and morphology in the range of 2 to 6 nm (6). As porous lattices completely covering the cell surface, the S-layers can provide prokaryotic cells with selective advantages by functioning as protective coats, as s...

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Section: Discussionmentioning

confidence: 99%

Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12

Merroun

Raff

Roßberg

et al. 2005

Appl Environ Microbiol

243

178

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“…Cultures of Citrobacter sp. (Yong and Macaskie, 1998), Acidithiobacillus ferrooxidans (Merroun et al, 2002), Bacillus sphaericus (Knopp et al, 2003), and Acinetobacter johnsonii (Boswell et al, 1999) have been demonstrated to remove uranium from water using a phosphate release mechanism. Under aerobic growth conditions, these microorganisms can accumulate phosphorus intracellularly in the form of polyphosphate (polyP) granules (Groenestijn et al, 1988;Tandoi et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Multiple mechanisms of uranium immobilization by Cellulomonas sp. strain ES6

Sivaswamy

Boyanov

Peyton

et al. 2010

Biotech & Bioengineering

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Removal of hexavalent uranium (U(VI)) from aqueous solution was studied using a Gram-positive facultative anaerobe, Cellulomonas sp. strain ES6, under anaerobic, non-growth conditions in bicarbonate and PIPES buffers. Inorganic phosphate was released by cells during the experiments providing ligands for formation of insoluble U(VI) phosphates. Phosphate release was most probably the result of anaerobic hydrolysis of intracellular polyphosphates accumulated by ES6 during aerobic growth. Microbial reduction of U(VI) to U(IV) was also observed. However, the relative magnitudes of U(VI) removal by abiotic (phosphate-based) precipitation and microbial reduction depended on the buffer chemistry. In bicarbonate buffer, X-ray absorption fine structure (XAFS) spectroscopy showed that U in the solid phase was present primarily as a non-uraninite U(IV) phase, whereas in PIPES buffer, U precipitates consisted primarily of U(VI)-phosphate. In both bicarbonate and PIPES buffer, net release of cellular phosphate was measured to be lower than that observed in U-free controls suggesting simultaneous precipitation of U and PO₄³⁻. In PIPES, U(VI) phosphates formed a significant portion of U precipitates and mass balance estimates of U and P along with XAFS data corroborate this hypothesis. High-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray spectroscopy (EDS) of samples from PIPES treatments indeed showed both extracellular and intracellular accumulation of U solids with nanometer sized lath structures that contained U and P. In bicarbonate, however, more phosphate was removed than required to stoichiometrically balance the U(VI)/U(IV) fraction determined by XAFS, suggesting that U(IV) precipitated together with phosphate in this system. When anthraquinone-2,6-disulfonate (AQDS), a known electron shuttle, was added to the experimental reactors, the dominant removal mechanism in both buffers was reduction to a non-uraninite U(IV) phase. Uranium immobilization by abiotic precipitation or microbial reduction has been extensively reported; however, the present work suggests that strain ES6 can remove U(VI) from solution simultaneously through precipitation with phosphate ligands and microbial reduction, depending on the environmental conditions. Cellulomonadaceae are environmentally relevant subsurface bacteria and here, for the first time, the presence of multiple U immobilization mechanisms within one organism is reported using Cellulomonas sp. strain ES6.

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“…(Macaskie et al, 1992;Young and Macaskie, 1995;Jeong et al, 1997) and of Bacillus sphaericus (Knopp, et al, 2003); others observed the accumulation of U(VI) as needlelike fibrils on the cell surface of S. cerevisiae (Strandberg, et al, 1981;Volesky and May-Philips, 1995). However, the mechanisms whereby microorganisms cause the precipitation of uranium are poorly understood, and the U-bearing precipitates have not been properly characterized.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of uranium mineralization by the yeast Saccharomyces cerevisiae

Ohnuki

Ozaki

Yoshida

et al. 2005

Geochimica et Cosmochimica Acta

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Laser Spectroscopic Studies of Interactions of U^VI with Bacterial Phosphate Species

Cited by 27 publications

References 47 publications

Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12

Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12

Multiple mechanisms of uranium immobilization by Cellulomonas sp. strain ES6

Mechanisms of uranium mineralization by the yeast Saccharomyces cerevisiae

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Laser Spectroscopic Studies of Interactions of UVI with Bacterial Phosphate Species

Cited by 27 publications

References 47 publications

Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12

Complexation of Uranium by Cells and S-Layer Sheets of Bacillus sphaericus JG-A12

Multiple mechanisms of uranium immobilization by Cellulomonas sp. strain ES6

Mechanisms of uranium mineralization by the yeast Saccharomyces cerevisiae

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Laser Spectroscopic Studies of Interactions of U^VI with Bacterial Phosphate Species