Field evidence of selenium bioreduction in a uranium‐contaminated aquifer

Williams, Kenneth H.; Wilkins, Michael J.; N'Guessan, A. Lucie; Arey, Bruce W.; Dodova, Elena N.; Dohnálková, Alice; Holmes, Dawn E.; Lovley, Derek R.; Long, Philip E.

doi:10.1111/1758-2229.12032

Cited by 57 publications

(41 citation statements)

References 41 publications

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“…In another study, Hydrogenophaga sp. accounted for 8% of the in situ microbial community in biofilms associated with aquifer sediments after acetate amendment (Williams et al, 2013). Finally, a Fe(II)-oxidizing Hydrogenophaga strain (P101) was isolated from Rifle groundwater under microaerophilic conditions (Chan, 2015); this strain had a facultative mixotrophic phenotype, in that it could grow on complex, low-concentration organic medium as well as ferrous minerals like FeS and FeCO 3 .…”

Section: Discussionmentioning

confidence: 99%

Metatranscriptomic Analysis Reveals Unexpectedly Diverse Microbial Metabolism in a Biogeochemical Hot Spot in an Alluvial Aquifer

et al. 2017

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Organic matter deposits in alluvial aquifers have been shown to result in the formation of naturally reduced zones (NRZs), which can modulate aquifer redox status and influence the speciation and mobility of metals, affecting groundwater geochemistry. In this study, we sought to better understand how natural organic matter fuels microbial communities within anoxic biogeochemical hot spots (NRZs) in a shallow alluvial aquifer at the Rifle (CO) site. We conducted a 20-day microcosm experiment in which NRZ sediments, which were enriched in buried woody plant material, served as the sole source of electron donors and microorganisms. The microcosms were constructed and incubated under anaerobic conditions in serum bottles with an initial N2 headspace and were sampled every 5 days for metagenome and metatranscriptome profiles in combination with biogeochemical measurements. Biogeochemical data indicated that the decomposition of native organic matter occurred in different phases, beginning with mineralization of dissolved organic matter (DOM) to CO2 during the first week of incubation, followed by a pulse of acetogenesis that dominated carbon flux after 2 weeks. A pulse of methanogenesis co-occurred with acetogenesis, but only accounted for a small fraction of carbon flux. The depletion of DOM over time was strongly correlated with increases in expression of many genes associated with heterotrophy (e.g., amino acid, fatty acid, and carbohydrate metabolism) belonging to a Hydrogenophaga strain that accounted for a relatively large percentage (~8%) of the metatranscriptome. This Hydrogenophaga strain also expressed genes indicative of chemolithoautotrophy, including CO2 fixation, H2 oxidation, S-compound oxidation, and denitrification. The pulse of acetogenesis appears to have been collectively catalyzed by a number of different organisms and metabolisms, most prominently pyruvate:ferredoxin oxidoreductase. Unexpected genes were identified among the most highly expressed (>98th percentile) transcripts, including acetone carboxylase and cell-wall-associated hydrolases with unknown substrates (numerous lesser expressed cell-wall-associated hydrolases targeted peptidoglycan). Many of the most highly expressed hydrolases belonged to a Ca. Bathyarchaeota strain and may have been associated with recycling of bacterial biomass. Overall, these results highlight the complex nature of organic matter transformation in NRZs and the microbial metabolic pathways that interact to mediate redox status and elemental cycling.

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Section: Discussionmentioning

confidence: 99%

Metatranscriptomic Analysis Reveals Unexpectedly Diverse Microbial Metabolism in a Biogeochemical Hot Spot in an Alluvial Aquifer

et al. 2017

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“…Excessive phosphate mining activities in the Blackfoot River Watershed in Idaho have substantially increased the selenium levels in the river (8). The reductive microbial selenium transformations of the selenium cycle, which converts water-soluble and toxic selenium oxyanions (SeO 4 2Ϫ and SeO 3 2Ϫ ) into sparingly soluble elemental selenium or metal selenides, are the basis of promising approaches to bioremediation (5,9,10).…”

Section: Selenium In the Environmentmentioning

confidence: 99%

“…Recently, Williams et al (10), by employing molecular microbial ecology tools, provided evidence for the reduction of SeO 4 2Ϫ to elemental selenium coupled to acetate oxidation in a field-scale experiment carried out in a uranium-contaminated aquifer near Rifle, CO. Bioreduced elemental selenium, with a diameter of 50 to 60 nm, accumulated within the biofilms formed on the tubing used to circulate acetate-amended groundwater through the soil. Phylogenic analysis of the biofilms showed a dominance of Dechloromonas sp.…”

Section: Ecology Of Selenium-reducing Bacteriamentioning

confidence: 99%

Ecology and Biotechnology of Selenium-Respiring Bacteria

Nancharaiah

2015

Microbiol Mol Biol Rev

362

232

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SUMMARY In nature, selenium is actively cycled between oxic and anoxic habitats, and this cycle plays an important role in carbon and nitrogen mineralization through bacterial anaerobic respiration. Selenium-respiring bacteria (SeRB) are found in geographically diverse, pristine or contaminated environments and play a pivotal role in the selenium cycle. Unlike its structural analogues oxygen and sulfur, the chalcogen selenium and its microbial cycling have received much less attention by the scientific community. This review focuses on microorganisms that use selenate and selenite as terminal electron acceptors, in parallel to the well-studied sulfate-reducing bacteria. It overviews the significant advancements made in recent years on the role of SeRB in the biological selenium cycle and their ecological role, phylogenetic characterization, and metabolism, as well as selenium biomineralization mechanisms and environmental biotechnological applications.

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“…As more stringent regulations come into force in order to limit the discharge of Se-containing waste, the use of bioremediation technologies are preferable because they will offer more cost-effective approaches for the removal of the pollutant. There has been a growing interest in the use of microorganisms in remediating Secontaminated environments (96)(97)(98)(99). In this context, a number of studies have been carried out in order to exploit the use of Seoxyanion-reducing microorganisms in small/large-scale remediation schemes.…”

Section: Selenium Bioremediationmentioning

confidence: 99%

Microbial Transformations of Selenium Species of Relevance to Bioremediation

Eswayah

Smith

Gardiner

2016

Appl Environ Microbiol

181

102

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b Selenium species, particularly the oxyanions selenite (SeO 3 2؊ ) and selenate (SeO 4 2؊ ), are significant pollutants in the environment that leach from rocks and are released by anthropogenic activities. Selenium is also an essential micronutrient for organisms across the tree of life, including microorganisms and human beings, particularly because of its presence in the 21st genetically encoded amino acid, selenocysteine. Environmental microorganisms are known to be capable of a range of transformations of selenium species, including reduction, methylation, oxidation, and demethylation. Assimilatory reduction of selenium species is necessary for the synthesis of selenoproteins. Dissimilatory reduction of selenate is known to support the anaerobic respiration of a number of microorganisms, and the dissimilatory reduction of soluble selenate and selenite to nanoparticulate elemental selenium greatly reduces the toxicity and bioavailability of selenium and has a major role in bioremediation and potentially in the production of selenium nanospheres for technological applications. Also, microbial methylation after reduction of Se oxyanions is another potentially effective detoxification process if limitations with low reaction rates and capture of the volatile methylated selenium species can be overcome. This review discusses microbial transformations of different forms of Se in an environmental context, with special emphasis on bioremediation of Se pollution. Since the discovery in 1954 by Pinsent that the oxidation of formate by cell suspensions of Escherichia coli requires growth medium containing molybdate and selenite, there has been a growing interest in the biochemical role of selenium in microorganisms (1). Se is an essential component of selenoamino acids, such as selenomethionine and selenocysteine (the 21st proteinogenic amino acid), that occur in certain types of prokaryotic enzymes. Indeed, the requirement for selenite in E. coli growing on formate is linked to the fact that formate dehydrogenase contains selenocysteine. Other prokaryotic enzymes that contain selenocysteine include glycine reductase in several clostridia, formate dehydrogenases in diverse prokaryotes, including Salmonella, Clostridium, and Methanococcus, as well as hydrogenases in Methanococcus and other anaerobes. In addition, other bacterial Se-dependent enzymes, in which the selenium is part of the active site molybdenum-containing cofactor, include nicotinic acid dehydrogenase and xanthine dehydrogenase, which is present in certain clostridial species (2-4).Reactions that are involved in the cycling of Se in soil, including those influenced by microbes, are diagrammatically summarized in Fig. 1 2Ϫ and was spatially separated from sulfate reduction in the environment despite the presence of substantial concentrations of sulfate where it occurred. Thus, it can be concluded that Se and S have different reductive biogeochemical cycles and appear to involve distinct populations of microorganisms.With respect to the remediation of sel...

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Field evidence of selenium bioreduction in a uranium‐contaminated aquifer

Cited by 57 publications

References 41 publications

Metatranscriptomic Analysis Reveals Unexpectedly Diverse Microbial Metabolism in a Biogeochemical Hot Spot in an Alluvial Aquifer

Metatranscriptomic Analysis Reveals Unexpectedly Diverse Microbial Metabolism in a Biogeochemical Hot Spot in an Alluvial Aquifer

Ecology and Biotechnology of Selenium-Respiring Bacteria

Microbial Transformations of Selenium Species of Relevance to Bioremediation

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