Plutonium(IV) Reduction by the Metal-Reducing Bacteria
            <i>Geobacter metallireducens</i>
            GS15 and
            <i>Shewanella oneidensis</i>
            MR1

Boukhalfa, Hakim; Icopini, Gary A.; Reilly, Sean D.; Neu, Mary P.

doi:10.1128/aem.00747-07

Cited by 70 publications

(69 citation statements)

References 29 publications

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“…can also solubilize solid Pu(IV)O 2(s) by reducing it to Pu(III) (24). Studies with the dissimilatory metal-reducing bacteria (DMRB) Geobacter metallireducens and Shewanella oneidensis reported the formation of inorganic Pu(IV) colloids after exposure to a mixture of Pu(V) and Pu(VI) under anoxic conditions (25) and the formation of Pu(III) in some cases (26)(27)(28). These laboratory studies demonstrate that Pu sorption to bacterial surfaces can be driven by a variety of mechanisms, including redox transformations, resulting in Pu products of different composition and stability.…”

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confidence: 99%

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Interactions of Plutonium with Pseudomonas sp. Strain EPS-1W and Its Extracellular Polymeric Substances

Boggs

Jiao

Dai

et al. 2016

Appl Environ Microbiol

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Safe and effective nuclear waste disposal, as well as accidental radionuclide releases, necessitates our understanding of the fate of radionuclides in the environment, including their interaction with microorganisms. We examined the sorption of Pu(IV) and Pu(V) to Pseudomonas sp. strain EPS-1W, an aerobic bacterium isolated from plutonium (Pu)-contaminated groundwater collected in the United States at the Nevada National Security Site (NNSS) in Nevada. We compared Pu sorption to cells with and without bound extracellular polymeric substances (EPS). Wild-type cells with intact EPS sorbed Pu(V) more effectively than cells with EPS removed. In contrast, cells with and without EPS showed the same sorption affinity for Pu(IV). In vitro experiments with extracted EPS revealed rapid reduction of Pu(V) to Pu(IV). Transmission electron microscopy indicated that 2-to 3-nm nanocrystalline Pu(IV)O 2 formed on cells equilibrated with high concentrations of Pu(IV) but not Pu(V). Thus, EPS, while facilitating Pu(V) reduction, inhibit the formation of nanocrystalline Pu(IV) precipitates. IMPORTANCEOur results indicate that EPS are an effective reductant for Pu(V) and sorbent for Pu(IV) and may impact Pu redox cycling and mobility in the environment. Additionally, the resulting Pu morphology associated with EPS will depend on the concentration and initial Pu oxidation state. While our results are not directly applicable to the Pu transport situation at the NNSS, the results suggest that, in general, stationary microorganisms and biofilms will tend to limit the migration of Pu and provide an important Pu retardation mechanism in the environment. In a broader sense, our results, along with a growing body of literature, highlight the important role of microorganisms as producers of redox-active organic ligands and therefore as modulators of radionuclide redox transformations and complexation in the subsurface.T he civil production of nuclear energy and military production of nuclear materials have resulted in an estimated worldwide inventory of over 2,000 metric tons of plutonium (Pu) (1). This inventory continues to increase at a rate of approximately 70 metric tons per year as a result of global nuclear energy production (2). Due to its long half-life (24,100 years for 239 Pu) and high radiotoxicity (3), Pu is an important driver in public health risk assessments for nuclear waste repositories and radiologically contaminated sites. However, predicting how Pu behaves in the environment and ultimately calculating its human health risk are limited by our understanding of the dominant biogeochemical processes controlling its behavior.The behavior of Pu in the environment is strongly dependent on its oxidation state and concentration. Among all the actinides, Pu has one of the most complex chemical, redox, and surface sorption behaviors. At low concentrations, Pu can exist as aqueous species in the III, IV, V, and/or VI oxidation states, all of which have different solubilities (4), mineral sorption affinities (5-7), and hence...

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“…Pu interaction with EPS is likely to induce redox transformations and, as a result, changes in Pu speciation and mobility. Compared to the reduction of Pu(IV) to Pu(III) that was observed under anoxic conditions (26,28), facile Pu(V, VI) reduction to Pu(IV) is expected to occur under oxic conditions (25).…”

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confidence: 99%

Interactions of Plutonium with Pseudomonas sp. Strain EPS-1W and Its Extracellular Polymeric Substances

Boggs

Jiao

Dai

et al. 2016

Appl Environ Microbiol

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“…The reduction of oxidized Pu species to Pu(IV) is desired, because it is highly insoluble and not very mobile. However, in the presence of complexing ligands and under reducing conditions the production of Pu(III) is favored, and Pu(III) complexes can be quite soluble (2). The conditions leading to the reduction of Pu(V) and Pu(VI) need to be understood and controlled so that they do not lead to the production of Pu(III), if the biological reduction of Pu(V) or Pu(VI) is to be used as an effective remediation strategy.…”

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confidence: 99%

“…Microorganisms can influence the chemical speciation, valence state, and distribution of actinides in subsurface environments (2,8,12,14). Dissimilatory metal-reducing bacteria (DMRB), which derive energy by respiring oxidized metals (Fe and Mn in nature), may play a particularly important role in the mobility of actinides, since the oxidized forms of many radionuclides are more mobile than their reduced forms.…”

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Plutonium(V/VI) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1

Icopini¹,

Lack²,

Hersman³

et al. 2009

Appl Environ Microbiol

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We examined the ability of the metal-reducing bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1 to reduce Pu(VI) and Pu(V). Cell suspensions of both bacteria reduced oxidized Pu [a mixture of Pu(VI) and Pu(V)] to Pu(IV). The rate of plutonium reduction was similar to the rate of U(VI) reduction obtained under similar conditions for each bacteria. The rates of Pu(VI) and U(VI) reduction by cell suspensions of S. oneidensis were slightly higher than the rates observed with G. metallireducens. The reduced form of Pu was characterized as aggregates of nanoparticulates of Pu(IV). Transmission electron microscopy images of the solids obtained from the cultures after the reduction of Pu(VI) and Pu(V) by S. oneidensis show that the Pu precipitates have a crystalline structure. The nanoparticulates of Pu(IV) were precipitated on the surface of or within the cell walls of the bacteria. The production of Pu(III) was not observed, which indicates that Pu(IV) was the stable form of reduced Pu under these experimental conditions. Experiments examining the ability of these bacteria to use Pu(VI) as a terminal electron acceptor for growth were inconclusive. A slight increase in cell density was observed for both G. metallireducens and S. oneidensis when Pu(VI) was provided as the sole electron acceptor; however, Pu(VI) concentrations decreased similarly in both the experimental and control cultures.

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“…Shewanella oneidensis MR-1 is a bacterial isolate belonging to the Shewanellaceae, a family distinguished by the wide variety of electron acceptors they can utilize (e.g., iron, manganese, uranium, chromium, and plutonium) (25)(26)(27)(28). Because of their flexible respiratory pathways, Shewanella species are recognized as potential agents for bioremediation at sites contaminated with heavy metals and radionuclides (29).…”

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Exploring the Roles of DNA Methylation in the Metal-Reducing Bacterium Shewanella oneidensis MR-1

et al. 2013

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We performed whole-genome analyses of DNA methylation in Shewanella oneidensis MR-1 to examine its possible role in regulating gene expression and other cellular processes. Single-molecule real-time (SMRT) sequencing revealed extensive methylation of adenine (N6mA) throughout the genome. These methylated bases were located in five sequence motifs, including three novel targets for type I restriction/modification enzymes. The sequence motifs targeted by putative methyltranferases were determined via SMRT sequencing of gene knockout mutants. In addition, we found that S. oneidensis MR-1 cultures grown under various culture conditions displayed different DNA methylation patterns. However, the small number of differentially methylated sites could not be directly linked to the much larger number of differentially expressed genes under these conditions, suggesting that DNA methylation is not a major regulator of gene expression in S. oneidensis MR-1. The enrichment of methylated GATC motifs in the origin of replication indicates that DNA methylation may regulate genome replication in a manner similar to that seen in Escherichia coli. Furthermore, comparative analyses suggest that many Gammaproteobacteria, including all members of the Shewanellaceae family, may also utilize DNA methylation to regulate genome replication.

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Plutonium(IV) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS15 and Shewanella oneidensis MR1

Cited by 70 publications

References 29 publications

Interactions of Plutonium with Pseudomonas sp. Strain EPS-1W and Its Extracellular Polymeric Substances

Interactions of Plutonium with Pseudomonas sp. Strain EPS-1W and Its Extracellular Polymeric Substances

Plutonium(V/VI) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1

Exploring the Roles of DNA Methylation in the Metal-Reducing Bacterium Shewanella oneidensis MR-1

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