Bioremediation of Selenium in Soil and Water

Losi, M. E.; Frankenberger, W. T.

doi:10.1097/00010694-199710000-00002

Cited by 57 publications

(31 citation statements)

References 45 publications

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“…In aerated environments, selenium occurs predominantly and naturally as the high-valence soluble forms selenate (SeO# − % , jVI) and selenite (SeO# − $ , jIV). These inorganic oxidized forms are abundant in some habitats, particularly through contamination of soil and drainage waters as a result of widespread use in industrial and agricultural processes (Losi & Frankenberger, 1997 toxic and mutagenic for bacteria and mammals (Noda et al, 1979 ;Stadtman, 1974). Consequently, selenium accumulation can cause important ecological problems such as in the Kesterson reservoir, in the San Joaquin Valley (California, USA), where selenium concentration resulted in extensive deformities and deaths in waterfowl and other wildlife (Ohlendorf & Santolo, 1994 ;Saiki & Lowe, 1987).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Involvement of a putative molybdenum enzyme in the reduction of selenate by Escherichia coli

et al. 2002

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Selenium oxyanions, particularly selenite, can be highly toxic to living organisms. Few bacteria reduce both selenate and selenite into the less toxic elemental selenium. Insights into the mechanisms of the transport and the reduction of selenium oxyanions in Escherichia coli were provided by a genetic analysis based on transposon mutagenesis. Ten mutants impaired in selenate reduction were analysed. Three of them were altered in genes encoding transport proteins including a porin, an inner-membrane protein and a sulfate carrier. Two mutants were altered in genes required for molybdopterin biosynthesis, strongly suggesting that the selenate reductase of E. coli is a molybdoenzyme. However, mutants deleted in various oxomolybdenum enzymes described so far in this species still reduced selenate. Finally, a mutant in the gene ygfK encoding a putative oxidoreductase was obtained. This gene is located upstream of ygfN and ygfM in the ygfKLMN putative operon. YgfN and YgfM code for a molybdopterin-containing enzyme and a polypeptide carrying a FAD domain, respectively. It is therefore proposed that the selenate reductase of E. coli is a structural complex including the proteins YgfK, YgfM and YgfN. In addition, all the various mutants were still able to reduce selenite into elemental selenium. This implies that the transport and reduction of this compound are clearly distinct from those of selenate.Keywords : molybdenum iron-sulfur protein, oxyanion reduction, selenite INTRODUCTIONSelenium is an essential trace nutrient for most living organisms (McKeehan et al., 1976 ;Shamberger, 1983). Small amounts of selenium are required to synthesize the amino acid selenocysteine present in a few proteins such as formate dehydrogenases and glycine reductase in prokaryotes (reviewed by Stadtman, 1996). In aerated environments, selenium occurs predominantly and naturally as the high-valence soluble forms selenate (SeO# − % , jVI) and selenite (SeO# − $ , jIV). These inorganic oxidized forms are abundant in some habitats, particularly through contamination of soil and drainage waters as a result of widespread use in industrial and agricultural processes (Losi & Frankenberger, 1997 toxic and mutagenic for bacteria and mammals (Noda et al., 1979 ;Stadtman, 1974). Consequently, selenium accumulation can cause important ecological problems such as in the Kesterson reservoir, in the San Joaquin Valley (California, USA), where selenium concentration resulted in extensive deformities and deaths in waterfowl and other wildlife (Ohlendorf & Santolo, 1994 ;Saiki & Lowe, 1987).In the biogeochemical cycle of selenium, various redox reactions are carried out by microorganisms. Several bacteria, including Escherichia coli (Turner et al., 1998) are able to reduce both selenate and selenite into elemental selenium (Se!), while certain species like Rhodobacter sphaeroides (Bebien et al., 2001 ;Van Fleet-Stalder et al., 2000) or Ralstonia metallidurans (Roux et al., 2001) reduce only selenite. The reduction of the bioavailable selenium oxyanions int...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Involvement of a putative molybdenum enzyme in the reduction of selenate by Escherichia coli

et al. 2002

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“…Abiotic reduction has also been observed but only under highly reducing conditions atypical of surface and shallow subsurface environments (Charlet et al, 2007;Myneni et al, 1997). Microbial reduction of bioavailable Se oxyanions to solid Se(0) is thus widely viewed as one of the primary attenuation pathways for Se in surface soils (Dungan and Frankenberger, 1999;Frankenberger and Arshad, 2001;Losi and Frankenberger, 1997a;Wu, 2004).…”

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confidence: 99%

Soil‐Aggregate‐Scale Heterogeneity in Microbial Selenium Reduction

Kausch

et al. 2012

Vadose Zone Journal

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Given the role of Se as both an environmental contaminant and a micronutrient, the microbial reduction and subsequent sequestration of bioavailable Se in soils are of great ecological interest. Primary particles in surface soils are typically bound into loosely packed, microporous aggregates, which may be critical spatial units in determining the fate of Se in soils. Surrounded by macropores where preferential flow rapidly advects dissolved compounds, soil aggregates are domains of slow diffusive transport where spatial variations in chemical concentrations and biogeochemical reactions can prevail. We conducted a series of controlled flow‐through experiments utilizing three‐dimensional, artificial soil aggregates (2.5‐cm i.d.) surrounded by a macropore. Aggregates were composed of either quartz sand or ferrihydrite‐coated sand inoculated with one of two Se‐reducing bacteria (Thauera selenatis or Enterobacter cloacae SLD1a‐1). Selenite export rates varied between 0.02 ± 0.01 and 3.4 ± 0.2 nmol h−1 g−1 as a function of aeration condition and input solution composition (higher SeO42− or C‐source concentrations led to higher SeO32− export). Oxic input conditions significantly decreased Se reduction; however, the detection of SeO32− in effluent samples indicates the occurrence of anoxic microzones within aggregates. Furthermore, we found that solid‐phase concentrations of reduced Se increased toward the core of aggregates and are estimated to at least double within the first millimeter into the aggregate under all conditions investigated. This indicates that concentrations of reduced Se may generally be expected to increase with distance from the advection boundary (macropore) inside aggregates, which would imply that soils with larger aggregates retain more Se.

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“…Finally, in addition to redox biotransformations, biomethylation may also increase the volatility of metals, with the methylation of mercury, cadmium, lead, tin, selenium and tellurium recorded (Diels et al 1995). These mechanisms could also offer potential use for the in situ remediation of contaminated soil (Losi & Frankenberger 1997).…”

Section: Enzymatically Catalysed Biotransformationmentioning

confidence: 99%