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Hosseini F, Hadian M, Lashani E, Moghimi H. Simultaneous bioreduction of tellurite and selenite by Yarrowia lipolytica, Trichosporon cutaneum, and their co-culture along with characterization of biosynthesized Te-Se nanoparticles. Microb Cell Fact 2023; 22:193. [PMID: 37749532 PMCID: PMC10519092 DOI: 10.1186/s12934-023-02204-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 09/18/2023] [Indexed: 09/27/2023] Open
Abstract
BACKGROUND Natural and anthropogenic activities, such as weathering of rocks and industrial processes, result in the release of toxic oxyanions such as selenium (Se) and tellurium (Te) into the environment. Due to the high toxicity of these compounds, their removal from the environment is vital. RESULTS In this study, two yeast strains, Yarrowia lipolytica and Trichosporon cutaneum, were selected as the superior strains for the bioremediation of tellurium and selenium. The reduction analyses showed that exposure to selenite induced more detrimental effects on the strains compared to tellurite. In addition, co-reduction of pollutants displayed almost the same results in selenite reduction and more than ~ 20% higher tellurite reduction in 50 h, which shows that selenite triggered higher tellurite reduction in both strains. The selenite and tellurite kinetics of removal were consistent with the first-order model because of their inhibitory behavior. The result of several characterization experiments, such as FE-SEM (Field emission scanning electron microscopy), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), and dispersive X-ray (EDX) on Te-Se nanoparticles (NPs) revealed that the separated Te-Se NPs were needle-like, spherical, and amorphous, consisted of Te-Se NPs ranging from 25 to 171 nm in size, and their surface was covered with different biomolecules. CONCLUSIONS Remarkably, this work shows, for the first time, the simultaneous bioreduction of tellurite and selenite and the production of Te-Se NPs using yeast strains, indicating their potential in this area, which may be applied to the nanotechnology industry and environmental remediation.
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Affiliation(s)
- Firooz Hosseini
- Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Maryam Hadian
- Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Elham Lashani
- Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Hamid Moghimi
- Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran.
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Lashani E, Moghimi H, J Turner R, Amoozegar MA. Selenite bioreduction by a consortium of halophilic/halotolerant bacteria and/or yeasts in saline media. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023:121948. [PMID: 37270053 DOI: 10.1016/j.envpol.2023.121948] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 05/18/2023] [Accepted: 05/31/2023] [Indexed: 06/05/2023]
Abstract
Selenium oxyanions are released into environments by natural and anthropogenic activities and are present in agricultural and glass manufacturing wastewater in several locations worldwide. Excessive amounts of this metalloid have adverse effects on the health of living organisms. Halophilic and halotolerant microorganisms were selected for selenium oxyanions remediation due to presence of significant amount of salt in selenium-containing wastewater. Effects of aeration, carbon sources, competitive electron acceptors, and reductase inhibitors were investigated on SeO32- bio-removal. Additionally, NO3--containing wastewater were exploited to investigate SeO32- remediation in synthetic agricultural effluents. The results showed that the SeO32- removal extent is maximum in aerobic conditions with succinate as a carbon source. SO42- and PO43- do not significantly interfere with SeO32- reduction, while WO42- and TeO32- decrease the SeO32- removal percentage (up to 35 and 37%, respectively). Furthermore, NO3- had an adverse effect on SeO32- biotransformation by our consortia. All consortia reduced SeO32- in synthetic agricultural wastewaters with a 45-53% removal within 120 h. This study suggests that consortia of halophilic/halotolerant bacteria and yeasts could be applied to treat SeO32--contaminated drainage water. In addition, sulphates, and phosphates do not interfere with selenite bioreduction by these consortia, which makes them suitable candidates for the bioremediation of selenium-containing wastewater.
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Affiliation(s)
- Elham Lashani
- Extremophiles Laboratory, Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
| | - Hamid Moghimi
- Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran.
| | - Raymond J Turner
- Microbial Biochemistry Laboratory, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada
| | - Mohammad Ali Amoozegar
- Extremophiles Laboratory, Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
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Extreme Environments and High-Level Bacterial Tellurite Resistance. Microorganisms 2019; 7:microorganisms7120601. [PMID: 31766694 PMCID: PMC6955997 DOI: 10.3390/microorganisms7120601] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 11/19/2019] [Accepted: 11/20/2019] [Indexed: 01/10/2023] Open
Abstract
Bacteria have long been known to possess resistance to the highly toxic oxyanion tellurite, most commonly though reduction to elemental tellurium. However, the majority of research has focused on the impact of this compound on microbes, namely E. coli, which have a very low level of resistance. Very little has been done regarding bacteria on the other end of the spectrum, with three to four orders of magnitude greater resistance than E. coli. With more focus on ecologically-friendly methods of pollutant removal, the use of bacteria for tellurite remediation, and possibly recovery, further highlights the importance of better understanding the effect on microbes, and approaches for resistance/reduction. The goal of this review is to compile current research on bacterial tellurite resistance, with a focus on high-level resistance by bacteria inhabiting extreme environments.
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Maltman C, Donald LJ, Yurkov V. Two distinct periplasmic enzymes are responsible for tellurite/tellurate and selenite reduction by strain ER-Te-48 associated with the deep sea hydrothermal vent tube worms at the Juan de Fuca Ridge black smokers. Arch Microbiol 2017; 199:1113-1120. [PMID: 28432382 DOI: 10.1007/s00203-017-1382-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/27/2017] [Accepted: 04/17/2017] [Indexed: 11/27/2022]
Abstract
Strain ER-Te-48 isolated from a deep-ocean hydrothermal vent tube worm is capable of resisting and reducing extremely high levels of tellurite, tellurate, and selenite, which are used for respiration anaerobically. Tellurite and tellurate reduction is accomplished by a periplasmic enzyme of 215 kDa comprised of 3 subunits (74, 42, and 25 kDa) in a 2:1:1 ratio. The optimum pH and temperature for activity is 8.0 and 35 °C, respectively. Tellurite reduction has a V max of 5.6 µmol/min/mg protein and a K m of 3.9 mM. In the case of the tellurate reaction, V max and K m were 2.6 µmol/min/mg protein and 2.6 mM, respectively. Selenite reduction is carried out by another periplasmic enzyme with a V max of 2.8 µmol/min/mg protein, K m of 12.1 mM, and maximal activity at pH 6.0 and 38 °C. This protein is 165 kDa and comprised of 3 subunits of 98, 44, and 23 kDa in a 1:1:1 ratio.
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Affiliation(s)
- Chris Maltman
- Department of Microbiology, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
| | - Lynda J Donald
- Department of Microbiology, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
| | - Vladimir Yurkov
- Department of Microbiology, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
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Tellurite and Tellurate Reduction by the Aerobic Anoxygenic Phototroph Erythromonas ursincola, Strain KR99 Is Carried out by a Novel Membrane Associated Enzyme. Microorganisms 2017; 5:microorganisms5020020. [PMID: 28422063 PMCID: PMC5488091 DOI: 10.3390/microorganisms5020020] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 04/12/2017] [Accepted: 04/16/2017] [Indexed: 11/17/2022] Open
Abstract
Erythromonas ursincola, strain KR99 isolated from a freshwater thermal spring of Kamchatka Island in Russia, resists and reduces very high levels of toxic tellurite under aerobic conditions. Reduction is carried out by a constitutively expressed membrane associated enzyme, which was purified and characterized. The tellurite reductase has a molecular weight of 117 kDa, and is comprised of two subunits (62 and 55 kDa) in a 1:1 ratio. Optimal activity occurs at pH 7.0 and 28 °C. Tellurite reduction has a Vmax of 5.15 µmol/min/mg protein and a Km of 3.36 mM. The enzyme can also reduce tellurate with a Vmax and Km of 1.08 µmol/min/mg protein and 1.44 mM, respectively. This is the first purified membrane associated Te oxyanion reductase.
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Heavy metal resistance in halophilicBacteriaandArchaea. FEMS Microbiol Lett 2016; 363:fnw146. [DOI: 10.1093/femsle/fnw146] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/20/2016] [Indexed: 12/25/2022] Open
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Maltman C, Yurkov V. The Effect of Tellurite on Highly Resistant Freshwater Aerobic Anoxygenic Phototrophs and Their Strategies for Reduction. Microorganisms 2015; 3:826-38. [PMID: 27682119 PMCID: PMC5023272 DOI: 10.3390/microorganisms3040826] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 11/02/2015] [Indexed: 11/18/2022] Open
Abstract
Six fresh water aerobic anoxygenic phototrophs (Erythromicrobium ezovicum, strain E1; Erythromicrobium hydrolyticum, E4(1); Erythromicrobium ramosum, E5; Erythromonas ursincola, KR99; Sandaracinobacter sibiricus, RB 16-17; and Roseococcus thiosulfatophilus, RB3) possessing high level resistance to TeO32− and the ability to reduce it to elemental Te were studied to understand their interaction with this highly toxic oxyanion. Tested organic carbon sources, pH, and level of aeration all had an impact on reduction. Physiological and metabolic responses of cells to tellurite varied among strains. In its presence, versus absence, cellular biomass either increased (KR99, 66.6% and E5, 21.2%) or decreased (RB3, 66.1%, E1, 57.8%, RB 16-17, 41.5%, and E4(1), 21.3%). The increase suggests a possible benefit from tellurite. Cellular ATP production was similarly affected, resulting in an increase (KR99, 15.2% and E5, 38.9%) or decrease (E4(1), 31.9%; RB 16-17, 48.8%; RB3, 55.9%; E1, 35.9%). Two distinct strategies to tellurite reduction were identified. The first, found in E4(1), requires de novo protein preparations as well as an undisturbed whole cell. The second strategy, in which reduction depended on a membrane associated constitutive reductase, was used by the remaining strains.
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Affiliation(s)
- Chris Maltman
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
| | - Vladimir Yurkov
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
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Bajaj M, Winter J. Se (IV) triggers faster Te (IV) reduction by soil isolates of heterotrophic aerobic bacteria: formation of extracellular SeTe nanospheres. Microb Cell Fact 2014; 13:168. [PMID: 25425453 PMCID: PMC4254260 DOI: 10.1186/s12934-014-0168-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 11/17/2014] [Indexed: 11/22/2022] Open
Abstract
Background Selenium and Tellurium have many common chemical properties as both belong to group 16 of the periodic table. High toxicities of Se and Te oxyanions cause environmental problems in contaminated soils and waters. Three strains (C4, C6 and C7) of selenite reducing and nanoparticle forming aerobic bacteria which were isolated from agricultural soils of India containing high concentrations of Se were investigated after 3.5 months of freeze-storage for their resistance against the toxic oxyanion tellurite and its reduction to non toxic elemental form Te0 as well as nanoparticles formation. Results Strains C4, C6 and C7 reduced tellurite at maximum reduction rates of 2.3, 1.5 and 2.1 mg Te (IV)/L/d, respectively and produced extracellular Te0 nanospheres as revealed from SEM-EDX analysis. Production of extracellular Te nanospheres has been described seldom. Further, concurrent reduction of both selenite and tellurite by bacteria was examined as these toxic oxyanions are often present together in natural environments, mine tailings or wastewater from copper refining. Interestingly, bioreduction of 100 mg/L selenite in shake flasks was not much affected by the presence of 10 mg/L tellurite but tellurite reduction rate increased 13 fold with selenite in the medium. The concurrent reduction of these oxyanions resulted in rarely described bioformation of extracellular nanoparticles composed of both Se and Te, reported first time for aerobically growing heterotrophic non-halophilic bacterial cultures. Duganella violacienigra, the closely related strain to C4 was also found to be resistant to oxyanions of Se and Te. Conclusions Selenite reducing heterotrophic non-halophilic aerobic bacteria revived from 3.5 months freeze storage could successfully reduce toxic tellurite to non toxic elemental form and produced extracellular nanospheres during detoxification. Presence of relatively less toxic selenite in the medium triggers bioreduction of more toxic tellurite leading to formation of extracellular SeTe nanospheres which are sought by solar and optical recording media industry because of their excellent photovoltaic and optical properties. The bacterial cultures investigated in this study could be exploited commercially to remediate not only selenite and tellurite-contaminated soil and water but also for green synthesis of extracellular Se, Te and Se + Te nanospheres.
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Affiliation(s)
- Mini Bajaj
- Institute of Biology for Engineers and Biotechnology of Wastewater, Am Fasanengarten, Karlsruhe Institute of Technology, Karlsruhe, 76133, Germany.
| | - Josef Winter
- Institute of Biology for Engineers and Biotechnology of Wastewater, Am Fasanengarten, Karlsruhe Institute of Technology, Karlsruhe, 76133, Germany.
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Alavi S, Amoozegar MA, Khajeh K. Enzyme(s) responsible for tellurite reducing activity in a moderately halophilic bacterium, Salinicoccus iranensis strain QW6. Extremophiles 2014; 18:953-61. [PMID: 24984690 DOI: 10.1007/s00792-014-0665-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 06/05/2014] [Indexed: 10/25/2022]
Abstract
Oxyanions of tellurium, like tellurate (TeO4 (2-)) and tellurite (TeO3 (2-)), are highly toxic for most microorganisms. There are a few reports on the bacterial tellurite resistance mechanism(s). Salinicoccus iranensis, a Gram-positive halophilic bacterium, shows high tellurite resistance and NADH-dependent tellurite reduction activity in vitro. Since little is known regarding TeO3 (2-) resistance mechanisms in halophilic microorganisms, here one of the enzymatic reduction activities presented in this microorganism is investigated. To enhance the enzymatic activity during purification, the effect of different parameters including time, inoculation, different pHs, different tellurite concentrations and different salts were optimized. We also examined the tellurite removal rates by diethyldithiocarbamate (DDTC) during optimization. In the culture medium the optimum conditions obtained showed that at 30 h, 2 % inoculum, pH 7.5, without tellurite and with 5 % NaCl (w/v) the highest enzyme activity and tellurite removal were observed. Results of the purification procedure done by hydroxyapatite batch-mode, ammonium sulfate precipitation, followed by phenyl-Sepharose and Sephadex G-100 column chromatography, showed that the enzyme consisted of three subunits with molecular masses of 135, 63 and 57 kDa. In addition to tellurite reduction activity, the enzyme was able to reduce nitrate too. Our study extends the knowledge regarding this process in halophilic microorganisms. Besides, this approach may suggest an application for the organism or the enzyme itself to be used for bioremediation of polluted areas with different contaminants due to its nitrate reductase activity.
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Affiliation(s)
- Sana Alavi
- Extremophiles Laboratory, Department of Microbiology, Faculty of Biology and Center of Excellence in Phylogeny of Living Organisms, College of Science, University of Tehran, P.O. Box 14155-6455, Tehran, Iran
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Transcriptional Response of Selenopolypeptide Genes and Selenocysteine Biosynthesis Machinery Genes in Escherichia coli during Selenite Reduction. Int J Microbiol 2014; 2014:394835. [PMID: 24839442 PMCID: PMC4009273 DOI: 10.1155/2014/394835] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Revised: 02/28/2014] [Accepted: 03/16/2014] [Indexed: 01/05/2023] Open
Abstract
Bacteria can reduce toxic selenite into less toxic, elemental selenium (Se0), but the mechanism on how bacterial cells reduce selenite at molecular level is still not clear. We used Escherichia coli strain K12, a common bacterial strain, as a model to study its growth response to sodium selenite (Na2SeO3) treatment and then used quantitative real-time PCR (qRT-PCR) to quantify transcript levels of three E. coli selenopolypeptide genes and a set of machinery genes for selenocysteine (SeCys) biosynthesis and incorporation into polypeptides, whose involvements in the selenite reduction are largely unknown. We determined that 5 mM Na2SeO3 treatment inhibited growth by ∼50% while 0.001 to 0.01 mM treatments stimulated cell growth by ∼30%. Under 50% inhibitory or 30% stimulatory Na2SeO3 concentration, selenopolypeptide genes (fdnG, fdoG, and fdhF) whose products require SeCys but not SeCys biosynthesis machinery genes were found to be induced ≥2-fold. In addition, one sulfur (S) metabolic gene iscS and two previously reported selenite-responsive genes sodA and gutS were also induced ≥2-fold under 50% inhibitory concentration. Our findings provide insight about the detoxification of selenite in E. coli via induction of these genes involved in the selenite reduction process.
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Amoozegar MA, Khoshnoodi M, Didari M, Hamedi J, Ventosa A, Baldwin SA. Tellurite removal by a tellurium-tolerant halophilic bacterial strain, Thermoactinomyces sp. QS-2006. ANN MICROBIOL 2011. [DOI: 10.1007/s13213-011-0343-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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12
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Fu L, Liu Q, Shen L, Wang Y. Proteomic study on sodium selenite-induced apoptosis of human cervical cancer HeLa cells. J Trace Elem Med Biol 2011; 25:130-7. [PMID: 21767938 DOI: 10.1016/j.jtemb.2011.06.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 05/29/2011] [Accepted: 06/20/2011] [Indexed: 12/27/2022]
Abstract
Sodium selenite can induce the apoptosis of cancer cells, however its mechanism has seldom been studied via proteomics. In this paper, human cervical cancer HeLa cells were investigated by MTT assay and morphological observation to get appropriate selenite concentrations for proteomic study. Results showed that selenite at concentrations larger than 10 μmol/L significantly inhibited the viability of HeLa cells. 40 μmol/L selenite was in the appropriate range for proteomic study. After 24 h treatment with 40 μmol/L selenite, total proteins were extracted from the cells and applied to two-dimensional gel electrophoresis (2DE). Those proteins with their expression levels altered at least 2-fold comparing to the control were picked up for protein identification via MALDI-TOF mass spectrometry and further confirmed by Western blot analysis. About 1000 spots were detected by the software in each 2DE gel, among which 13 differentially expressed proteins were identified by mass spectrometry and most of them are relevant to oxidative stress, such as peroxiredoxins, superoxide dismutase, quinolinate phosphoribosyl transferase, and D-dopachrome tautomerase. Meanwhile, reactive oxygen species (ROS) and mitochondrial membrane potential were also detected by flow cytometry and laser confocal scanning microscope. An increase in ROS generation and a decrease in mitochondrial membrane potential were detected in the selenite-treated cells compared with the control, which are consistent with the down-expression of antioxidative proteins in proteomics. Those results indicate that selenite induces the apoptosis of HeLa cells via ROS-mediated mitochondrial pathway. The present study also implies the potentiality of selenium in cervical cancer treatment.
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Affiliation(s)
- Liping Fu
- College of Life Sciences, Shenzhen University, Shenzhen 518060, China
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Wang X, Liu G, Zhou J, Wang J, Jin R, Lv H. Quinone-mediated reduction of selenite and tellurite by Escherichia coli. BIORESOURCE TECHNOLOGY 2011; 102:3268-3271. [PMID: 21145234 DOI: 10.1016/j.biortech.2010.11.078] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2010] [Revised: 11/17/2010] [Accepted: 11/17/2010] [Indexed: 05/30/2023]
Abstract
The reduction of selenite (Se(IV)) and tellurite (Te(IV)) by Escherichia coli was significantly enhanced by various quinone redox mediators (lawsone, menadione, anthraquinone-2-sulfonate, and anthraquinone-2,6-disulfonate). In the presence of 0.2mM lawsone, over 99.1% Se(IV) and around 96.4% Te(IV) were reduced in 8 h, at average reduction rates of 9.1 and 7.6 mM g cell(-1) h(-1), respectively. Better mediated reduction of Se(IV) and Te(IV) were observed when lawsone concentration increased from 0.1 to 0.4 mM and cell concentration increased from 0.1 to 0.6 g l(-1), respectively. Transmission electron microscopy analysis revealed the formation of both intracellular and extracellular Se(0) nanospheres or Te(0) nanorods, and the presence of lawsone increased the formation and accumulation of extracellular precipitates. The efficient mediated microbial reduction of Se(IV)/Te(IV) may be exploited for pollution removal and biological nanomaterials production.
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Affiliation(s)
- Xiujuan Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, Dalian University of Technology, Dalian, China
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Abstract
This report demonstrated selenite is transported through a monocarboxylate transporter Jen1p in Saccharomyces cerevisiae. Jen1p determined selenite sensitivity and uptake. Selenite had a similar affinity for Jen1p and a similar transport mechanism to the monocarboxylate lactate, which are both proton driven and exhibit reciprocal inhibition. Selenium is a micronutrient in most eukaryotes, including humans, which is well known for having an extremely thin border between beneficial and toxic concentrations. Soluble tetravalent selenite is the predominant environmental form and also the form that is applied in the treatment of human diseases. To acquire this nutrient from low environmental concentrations as well as to avoid toxicity, a well-controlled transport system is required. Here we report that Jen1p, a proton-coupled monocarboxylate transporter in S. cerevisiae, catalyzes high-affinity uptake of selenite. Disruption of JEN1 resulted in selenite resistance, and overexpression resulted in selenite hypersensitivity. Transport assay showed that overexpression of Jen1p enables selenite accumulation in yeast compared with a JEN1 knock out strain, indicating the Jen1p transporter facilitates selenite accumulation inside cells. Selenite uptake by Jen1p had a Km of 0.91 mM, which is comparable to the Km for lactate. Jen1p transported selenite in a proton-dependent manner which resembles the transport mechanism for lactate. In addition, selenite and lactate can inhibit the transport of each other competitively. Therefore, we postulate selenite is a molecular mimic of monocarboxylates which allows selenite to be transported by Jen1p.
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Affiliation(s)
- Joseph R McDermott
- Department of Biological Sciences, Oakland University, Rochester, MI 48309, USA
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