A novel method for the measurement of elemental selenium produced by bacterial reduction of selenite

Biswas, Keka C.; Barton, Larry L.; Tsui, Wai Lok; Shuman, Kevin E.; Gillespie, Jacquelyn; Eze, Chioma S.

doi:10.1016/j.mimet.2011.04.009

Cited by 78 publications

(41 citation statements)

References 32 publications

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“…Se 0 concentration was measured spectrophotometrically by using the method described in [62]. A standard for elemental selenium was prepared by reducing selenite to amorphous red Se 0 as follows: aliquots of a 0.1 M sodium selenite solution were placed in test tubes to give a range of 1 to 10 μmol selenite per tube.…”

Section: Methodsmentioning

confidence: 99%

Delayed formation of zero-valent selenium nanoparticles by Bacillus mycoides SeITE01 as a consequence of selenite reduction under aerobic conditions

et al. 2014

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BackgroundSelenite (SeO32−) oxyanion shows severe toxicity to biota. Different bacterial strains exist that are capable of reducing SeO32− to non-toxic elemental selenium (Se0), with the formation of Se nanoparticles (SeNPs). These SeNPs might be exploited for technological applications due to their physico-chemical and biological characteristics. The present paper discusses the reduction of selenite to SeNPs by a strain of Bacillus sp., SeITE01, isolated from the rhizosphere of the Se-hyperaccumulator legume Astragalus bisulcatus.ResultsUse of 16S rRNA and GyrB gene sequence analysis positioned SeITE01 phylogenetically close to B. mycoides. On agarized medium, this strain showed rhizoid growth whilst, in liquid cultures, it was capable of reducing 0.5 and 2.0 mM SeO32− within 12 and 24 hours, respectively. The resultant Se0 aggregated to form nanoparticles and the amount of Se0 measured was equivalent to the amount of selenium originally added as selenite to the growth medium. A delay of more than 24 hours was observed between the depletion of SeO32 and the detection of SeNPs. Nearly spherical-shaped SeNPs were mostly found in the extracellular environment whilst rarely in the cytoplasmic compartment. Size of SeNPs ranged from 50 to 400 nm in diameter, with dimensions greatly influenced by the incubation times. Different SeITE01 protein fractions were assayed for SeO32− reductase capability, revealing that enzymatic activity was mainly associated with the membrane fraction. Reduction of SeO32− was also detected in the supernatant of bacterial cultures upon NADH addition.ConclusionsThe selenite reducing bacterial strain SeITE01 was attributed to the species Bacillus mycoides on the basis of phenotypic and molecular traits. Under aerobic conditions, the formation of SeNPs were observed both extracellularly or intracellullarly. Possible mechanisms of Se0 precipitation and SeNPs assembly are suggested. SeO32− is proposed to be enzimatically reduced to Se0 through redox reactions by proteins released from bacterial cells. Sulfhydryl groups on peptides excreted outside the cells may also react directly with selenite. Furthermore, membrane reductases and the intracellular synthesis of low molecular weight thiols such as bacillithiols may also play a role in SeO32− reduction. Formation of SeNPs seems to be the result of an Ostwald ripening mechanism.

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Section: Methodsmentioning

confidence: 99%

Delayed formation of zero-valent selenium nanoparticles by Bacillus mycoides SeITE01 as a consequence of selenite reduction under aerobic conditions

et al. 2014

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“…However, this genus includes strictly aerobic, chemoorganoheterotrophic bacteria which induce precipitation of Fe oxyhydroxides particularly in surface waters (Spring 2006). Therefore, the incidence of the occurrence of native selenium and the oxidation of pyrite with bacteria of the genus Leptothrix seem unlikely, but the bacterial influence on the origin of native Se at the described locality cannot in general be excluded either (Blum et al 1998;Biswas et al 2011).…”

Section: Discussionmentioning

confidence: 99%

The origin of native selenium microparticles during the oxidation of sideritic mudstones in the Veřovice Formation (Outer Western Carpathians)

Matýsek¹,

Skupien²

2015

Geologica Carpathica

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Microparticles of native selenium were detected in weathered sideritic mudstones of the Veřovice Formation (Aptian) of the Silesian Unit (Outer Western Carpatians, NE part of the Czech Republic). This mineral forms small needle-like crystals with lengths of up to 20 µm, and is confined to fissures in sideritic mudstones covered by goethite or rarely also by hydrated Mn-oxide minerals. The oxidized sideritic mudstones show zonal structure and resemble the initial stage of the formation of the so-called rattle stones. From the superposition of phase diagrams of selenium and Fe-oxyhydroxides, Fe apparently occupies a large field in which Se(0) and FeOOH and/or Fe(OH) 3 can co-exist. The reduction of selenites or selenates by pyrite or by any other phase, capable of charge transfer, is likely to have been responsible for the formation of microparticles of native selenium. The crucial factor controlling the origin of these particles is the extremely low solubility of Se(0). The source of Se is not obvious. It can be released in trace concentrations during the weathering of pyrite. Sediments of the Veřovice Formation correspond to the anoxic event OAE1b and accumulation of siderophile elements in similar sediments is very probable. A probable mechanism for the origin of Se microcrystals is gradual crystallization from solution.Key words: Western Carpathians, Lower Cretaceous, sideritic mudstones, native selenium.gin during the process of weathering. In the area of the Western Carpathians there is only one reference to the occurrence of microparticles of selenium sitting on a crystal of pyrite (Szełęg et al. 2013). Here selenium forms needle-like crystals with a maximum length of 30 µm growing together with barite on a (001) crystal plane of partly oxidized pyrite about 4 mm in size. This occurrence comes from low-temperature hydrothermal veins of the Godula Formation of the Silesian Unit (Senonian). The aim of the paper is to document two new occurrences of native selenium in sideritic mudstones of the Veřovice Formation, Outer Western Carpathians and to discuss their origin. Methods of investigationThe crystals of selenium were identified during a brief study of the products of weathering of sideritic mudstones using electron microscopy and energy dispersive microanalysis carried out on untreated flat samples. The nature of the crystals does not allow preparation of polished thin sections or their metal coating using the sputtering process in a plasma environment. It was also found that, when carrying out electron probe microanalyses, some damage to analysed grains may occur including their burning through, which leads during the analysis to a gradual increase in the content of elements originating from the substrate, which may not be present in the analysed grains. These mainly include the contents of oxygen and iron and/or manganese. A typical EDX (Energy Dispersive X-ray Spectroscopy) spectrum of selenium particles is shown in Fig. 2. Therefore, the only available solution is to minimize the time needed ...

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“…Dissolved Se(VI) and Se(IV) concentrations were measured with a Dionex DX-120 ion chromatograph with a DionexIonPac AS9-HC analytical column and a12 mM Na 2 CO 3 eluent at 1.0 ml min -1 flowrate.No sulfate anions were observed to be present in ion chromatographs of samples from cell suspensions.Dissolved lactate and acetate concentrations were quantified using an Agilent Technologies 1260 Infinity SeriesHPLC with a Hamilton PRP-X300 analytical column and a 0.5 mM H 2 SO 4 eluent at 2ml min -1 flowrate and UV detection at 210 nm. Elemental Se was quantified by a colorimetric method (Biswas et al, 2011).Briefly, the centrifuged solids containing cells andSe 0were acidified with 2 ml of 0.1 M HCl to halt cell activity, centrifuged, and washed with 1 M NaCl. The remaining Se(0) was combined with a colorless solution of 1 M Na 2 S that produced an orange-red color upon sulfidization of Se(0…”

Section: Methodsmentioning

confidence: 99%

Oxygen kinetic isotope effects in selenate during microbial reduction

Schellenger

Onnis‐Hayden

Jaisi

et al. 2015

Applied Geochemistry

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The redox cycling of selenium oxyanions, elemental selenium, and selenides within water resources has implications for Se bioavailability and ecotoxicity. Dual stable isotope analysis of Se and O may provide important information for interpreting environmental Se transformations. Stable Se isotope systematics within the Se redox cycle has been well characterized within the literature, however concomitant oxygen isotope composition requires additional investigation. This study reports the O isotope fractionation of selenate (SeO 4 2-) during microbial reduction by the dissimilatory Sereducing bacterium Sulfurospirillum barnesii SES-3. Microbial reduction experiments were conducted under various conditions in order to investigate the range of 18 O enrichment factors ( O) in selenate. The reduction of selenate to selenite coupled to the oxidation of lactate to acetate resulted in an 18 O kinetic isotope effect with  O values 1.5-5.8 ‰. Greater 18 O enrichment was observed with increasing pH, but no correlation was found between  O and reduction rates, lactate availability, or cell density.  O values from biotic reduction by S. barnesii here are significantly less than those observed for abiotic reduction with Fe(II)-rich minerals reported in the literature, and this difference could be explained by a diffusion limitation during enzymatic reduction. Our results expand the isotope systematics of the selenium redox cycle and suggest  O has potential usefulness as indicators for in situ selenate reduction.

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A novel method for the measurement of elemental selenium produced by bacterial reduction of selenite

Cited by 78 publications

References 32 publications

Delayed formation of zero-valent selenium nanoparticles by Bacillus mycoides SeITE01 as a consequence of selenite reduction under aerobic conditions

Delayed formation of zero-valent selenium nanoparticles by Bacillus mycoides SeITE01 as a consequence of selenite reduction under aerobic conditions

The origin of native selenium microparticles during the oxidation of sideritic mudstones in the Veřovice Formation (Outer Western Carpathians)

Oxygen kinetic isotope effects in selenate during microbial reduction

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