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Ruiz-Fresneda MA, Lazúen-López G, Pérez-Muelas E, Peña-Martín J, Linares-Jiménez RE, Newman-Portela AM, Merroun ML. Identification of a multi-modal mechanism for Se(VI) reduction and Se(0) allotropic transition by Stenotrophomonas bentonitica. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024:10.1007/s11356-024-34256-z. [PMID: 38995337 DOI: 10.1007/s11356-024-34256-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Accepted: 07/02/2024] [Indexed: 07/13/2024]
Abstract
Microorganisms can play a key role in selenium (Se) bioremediation and the fabrication of Se-based nanomaterials by reducing toxic forms (Se(VI) and Se(IV)) into Se(0). In recent years, omics have become a useful tool in understanding the metabolic pathways involved in the reduction process. This paper aims to elucidate the specific molecular mechanisms involved in Se(VI) reduction by the bacterium Stenotrophomonas bentonitica. Both cytoplasmic and membrane fractions were able to reduce Se(VI) to Se(0) nanoparticles (NPs) with different morphologies (nanospheres and nanorods) and allotropes (amorphous, monoclinic, and trigonal). Proteomic analyses indicated an adaptive response against Se(VI) through the alteration of several metabolic pathways including those related to energy acquisition, synthesis of proteins and nucleic acids, and transport systems. Whilst the thioredoxin system and the Painter reactions were identified to play a crucial role in Se reduction, flagellin may also be involved in the allotropic transformation of Se. These findings suggest a multi-modal reduction mechanism is involved, providing new insights for developing novel strategies in bioremediation and nanoparticle synthesis for the recovery of critical materials within the concept of circular economy.
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Affiliation(s)
| | - Guillermo Lazúen-López
- Department of Microbiology, University of Granada, Campus Fuentenueva, 18071, Granada, Spain
| | - Eduardo Pérez-Muelas
- Department of Microbiology, University of Granada, Campus Fuentenueva, 18071, Granada, Spain
| | - Jesús Peña-Martín
- Department of Human Anatomy and Embryology, Faculty of Medicine, University of Granada, 18016, Granada, Spain
- Centre for Biomedical Research (CIBM), Biopathology and Regenerative Medicine Institute (IBIMER), University of Granada, 18100, Granada, Spain
| | - Raúl Eduardo Linares-Jiménez
- Department of Microbiology, University of Granada, Campus Fuentenueva, 18071, Granada, Spain
- Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | | | - Mohamed Larbi Merroun
- Department of Microbiology, University of Granada, Campus Fuentenueva, 18071, Granada, Spain
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Huynh TN, Stewart V. Purine catabolism by enterobacteria. Adv Microb Physiol 2023; 82:205-266. [PMID: 36948655 DOI: 10.1016/bs.ampbs.2023.01.001] [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] [Indexed: 02/13/2023]
Abstract
Purines are abundant among organic nitrogen sources and have high nitrogen content. Accordingly, microorganisms have evolved different pathways to catabolize purines and their metabolic products such as allantoin. Enterobacteria from the genera Escherichia, Klebsiella and Salmonella have three such pathways. First, the HPX pathway, found in the genus Klebsiella and very close relatives, catabolizes purines during aerobic growth, extracting all four nitrogen atoms in the process. This pathway includes several known or predicted enzymes not previously observed in other purine catabolic pathways. Second, the ALL pathway, found in strains from all three species, catabolizes allantoin during anaerobic growth in a branched pathway that also includes glyoxylate assimilation. This allantoin fermentation pathway originally was characterized in a gram-positive bacterium, and therefore is widespread. Third, the XDH pathway, found in strains from Escherichia and Klebsiella spp., at present is ill-defined but likely includes enzymes to catabolize purines during anaerobic growth. Critically, this pathway may include an enzyme system for anaerobic urate catabolism, a phenomenon not previously described. Documenting such a pathway would overturn the long-held assumption that urate catabolism requires oxygen. Overall, this broad capability for purine catabolism during either aerobic or anaerobic growth suggests that purines and their metabolites contribute to enterobacterial fitness in a variety of environments.
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Affiliation(s)
- TuAnh Ngoc Huynh
- Department of Food Science, University of Wisconsin, Madison, WI, United States
| | - Valley Stewart
- Department of Microbiology & Molecular Genetics, University of California, Davis, CA, United States.
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Peng X, Li T, Zheng Q, Lu Y, He Y, Tang Y, Qiu R. Citrobacter sp. Y3 harbouring novel gene HBCD-hd-1 mineralizes hexabromocyclododecane via new metabolic pathways according to multi-omics characterization. JOURNAL OF HAZARDOUS MATERIALS 2023; 442:130071. [PMID: 36183513 DOI: 10.1016/j.jhazmat.2022.130071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/24/2022] [Accepted: 09/24/2022] [Indexed: 06/16/2023]
Abstract
Hexabromocyclododecane (HBCD) is a typical persistent organic pollutant that is widely detected in the environment. Despite the significant efforts put into its mineralisation, there is still a lack of microorganism resources that can completely mineralise HBCD. Stable isotope analysis revealed that the Citrobacter sp. Y3 can use [13C]HBCD as its sole carbon source and degrade or even mineralise it into 13CO2, with a maximum conversion rate of 100% in approximately 14 days. Strain Y3 could completely mineralise HBCD, which it used as its only carbon source, and six debromination enzymes related to HBCD degradation were found in Y3, including haloalkane dehalogenase (DhaA), haloacid dehalogenase (HAD), etc. A functional gene named HBCD-hd-1, encoding a HAD, was found to be upregulated during HBCD degradation and heterologously expressed in Escherichia coli. Recombinant E. coli with the HBCD-hd-1 gene transformed the typical intermediate 4-bromobutyric acid to 4-hydroxybutanoic acid and showed excellent degradation performance on HBCD, accompanied by nearly 100% bromine (Br) ion generation. The expression of HBCD-hd-1 in Y3 rapidly accelerated the biodegradation of HBCD. With HBCD as its sole carbon source, strain Y3 could potentially degrade HBCD, especially in a low-nutrient environment.
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Affiliation(s)
- Xingxing Peng
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China.
| | - Tianyu Li
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China
| | - Qihang Zheng
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China
| | - Yingyuan Lu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China
| | - Yuzhe He
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China
| | - Yetao Tang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Rongliang Qiu
- Guangdong Provincial Key Laboratory of Agricultural & Rural Pollution Abatement and Environmental Safety, College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou 510642, China.
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Motlagh MK, Noroozifar M, Sodhi RNS, Kraatz H. Development of a Bacterial Enzyme‐Based Biosensor for the Detection and Quantification of Selenate. Chemistry 2022; 28:e202200953. [DOI: 10.1002/chem.202200953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Indexed: 11/09/2022]
Affiliation(s)
- Mozhgan Khorasani Motlagh
- Department Physical and Environmental Sciences University of Toronto Scarborough 1265 Military Trail Toronto M1C1A4 Ontario Canada
| | - Meissam Noroozifar
- Department Physical and Environmental Sciences University of Toronto Scarborough 1265 Military Trail Toronto M1C1A4 Ontario Canada
| | - Rana N. S. Sodhi
- Ontario Centre for Characterisation of Advanced Materials Department of Chemical Engineering & Applied Chemistry University of Toronto 2200 College Street Toronto M5S 3E5 Ontario Canada
| | - Heinz‐Bernhard Kraatz
- Department Physical and Environmental Sciences University of Toronto Scarborough 1265 Military Trail Toronto M1C1A4 Ontario Canada
- Department of Chemistry University of Toronto 280 St. George St. Toronto M5S 3H6 Ontario Canada
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Abstract
Selenium nanoparticles (SeNPs) are gaining importance in the food and medical fields due to their antibacterial properties. The microbial inhibition of these kinds of particles has been tested in a wide range of Gram (+) and Gram (−) pathogenic bacteria. When SeNPs are synthesized by biological methods, they are called biogenic SeNPs, which have a negative charge caused by their interaction between surface and capping layer (bioorganic material), producing their high stability. This review is focused on SeNPs synthesis by bacteria and summarizes the main factors that influence their main characteristics: shape, size and surface charge, considering the bacteria growth conditions for their synthesis. The different mechanisms of antimicrobial activity are revised, and this review describes several biosynthesis hypotheses that have been proposed due to the fact that the biological mechanism of SeNP synthesis is not fully known.
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Staicu LC, Barton LL. Selenium respiration in anaerobic bacteria: Does energy generation pay off? J Inorg Biochem 2021; 222:111509. [PMID: 34118782 DOI: 10.1016/j.jinorgbio.2021.111509] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/18/2021] [Accepted: 05/30/2021] [Indexed: 01/03/2023]
Abstract
Selenium (Se) respiration in bacteria was revealed for the first time at the end of 1980s. Although thermodynamically-favorable, energy-dense and documented in phylogenetically-diverse bacteria, this metabolic process appears to be accompanied by a number of challenges and numerous unanswered questions. Selenium oxyanions, SeO42- and SeO32-, are reduced to elemental Se (Se0) through anaerobic respiration, the end product being solid and displaying a considerable size (up to 500 nm) at the bacterial scale. Compared to other electron acceptors used in anaerobic respiration (e.g. N, S, Fe, Mn, and As), Se is one of the few elements whose end product is solid. Furthermore, unlike other known bacterial intracellular accumulations such as volutin (inorganic polyphosphate), S0, glycogen or magnetite, Se0 has not been shown to play a nutritional or ecological role for its host. In the context of anaerobic respiration of Se oxyanions, biogenic Se0 appears to be a by-product, a waste that needs proper handling, and this raises the question of the evolutionary implications of this process. Why would bacteria use a respiratory substrate that is useful, in the first place, and then highly detrimental? Interestingly, in certain artificial ecosystems (e.g. upflow bioreactors) Se0 might help bacterial cells to increase their density and buoyancy and thus avoid biomass wash-out, ensuring survival. This review article provides an in-depth analysis of selenium respiration (model selenium respiring bacteria, thermodynamics, respiratory enzymes, and genetic determinants), complemented by an extensive discussion about the evolutionary implications and the properties of biogenic Se0 using published and original/unpublished results.
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Affiliation(s)
- Lucian C Staicu
- Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland.
| | - Larry L Barton
- Department of Biology, University of New Mexico, MSCO3 2020, Albuquerque, NM 87131, USA
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Horsing around: Escherichia coli ST1250 of equine origin harbouring epidemic IncHI1/ST9 plasmid with bla CTX-M-1 and an operon for short-chain fructooligosaccharides metabolism. Antimicrob Agents Chemother 2021; 65:AAC.02556-20. [PMID: 33619063 PMCID: PMC8092906 DOI: 10.1128/aac.02556-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The relatedness of the equine-associated Escherichia coli ST1250 and its single- and double-locus variants (ST1250-SLV/DLV), obtained from horses in Europe, was studied by comparative genome analysis. A total of 54 isolates of E. coli ST1250 and ST1250-SLV/DLV from healthy and hospitalized horses across Europe [Czech Republic (n=23), the Netherlands (n=18), Germany (n=9), Denmark (n=3) and France (n=1)] from 2008-2017 were subjected to whole-genome sequencing. An additional 25 draft genome assemblies of E. coli ST1250 and ST1250-SLV/DLV were obtained from the public databases. The isolates were compared for genomic features, virulence genes, clade structure and plasmid content. The complete nucleotide sequences of eight IncHI1/ST9 and one IncHI1/ST2 plasmids were obtained using long-read sequencing by PacBio or MinION. In the collection of 79 isolates, only 10 were phylogenetically close (<8 SNP). The majority of isolates belonged to phylogroup B1 (73/79, 92.4%) and carried bla CTX-M-1 (58/79, 73.4%). The plasmid content of the isolates was dominated by IncHI1 of ST9 (56/62, 90.3%) and ST2 (6/62, 9.7%), while 84.5% (49/58) bla CTX-M-1 genes were associated with presence of IncHI1 replicon of ST9 and 6.9% (4/58) with IncHI1 replicon of ST2 within the corresponding isolates. The operon for the utilization of short chain fructooligosaccharides (fos operon) was present in 55 (55/79, 69.6%) isolates, and all of these carried IncHI1/ST9 plasmids. The eight complete IncHI1/ST9 plasmid sequences showed the presence of bla CTX-M-1 and the fos operon within the same molecule. Sequences of IncHI1/ST9 plasmids were highly conserved (>98% similarity) regardless of country of origin and varied only in the structure and integration site of MDR region. E. coli ST1250 and ST1250-SLV/DLV are phylogenetically-diverse strains associated with horses. A strong linkage of E. coli ST1250 with epidemic multi-drug resistance plasmid lineage IncHI1/ST9 carrying bla CTX-M-1 and the fos operon was identified.
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Microbial consortia capable of reducing selenate in the presence of nitrate enriched from coalmining-impacted environments. Appl Microbiol Biotechnol 2021; 105:1287-1300. [PMID: 33443632 DOI: 10.1007/s00253-020-11059-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 10/14/2020] [Accepted: 12/11/2020] [Indexed: 10/22/2022]
Abstract
Biological treatment to remove dissolved selenium from mine-impacted water is often inhibited by the co-contaminant nitrate. In this work, we enriched microbial consortia capable of removing dissolved selenium in the presence of nitrate from native bacteria at sites influenced by coalmine seepages with elevated concentrations of Se, nitrate, and sulfate. Enrichments were collected from sediments in different vegetated or non-vegetated seepage collection ponds, and all demonstrated the potential for dissolved selenium removal. Nitrate inhibited dissolved selenium removal rates in four of these enrichments. However, microorganisms enriched from a mine seepage influenced natural vegetated marsh removed dissolved Se and nitrate simultaneously. Additionally, enrichments from one seepage collection pond achieved enhanced dissolved selenium removal in the presence of nitrate. Based on functional metagenomics, the dominant species with the metabolic capacity for selenate reduction were classified in Orders Enterobacterales and Clostridiales. Most putative selenate reductases identified as either ygfK, associated with selenoprotein synthesis or production of methylated organoselenium compounds, and narG, nitrate reductases with an affinity also for selenate.Key points• Enriched mine influenced sediment bacteria have the capacity for removal of dissolved Se species.• Consortia from a vegetated natural marsh reduced Se without inhibition from nitrate.• Nitrate stimulated the removal of Se by consortia from a disused tailing pond.
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Shi LD, Lv PL, Niu ZF, Lai CY, Zhao HP. Why does sulfate inhibit selenate reduction: Molybdenum deprivation from Mo-dependent selenate reductase. WATER RESEARCH 2020; 178:115832. [PMID: 32335368 DOI: 10.1016/j.watres.2020.115832] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/07/2020] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
Selenium pollution has become an increasingly serious global concern. Methane-fed selenate reduction has proven to be of great interest for the bioremediation of selenate-contaminated waters even with the coexistence of nitrate and dissolved oxygen. However, it is unclear if the common concurrent sulfate anion affects selenate removal. To address this question, we first introduced selenate (SeO42-) as the sole influent electron acceptor in a CH4-fed membrane biofilm reactor (CH4-MBfR); then we added different concentrations of sulfate (SO42-). The initial selenate removal efficiency (∼90%) was decreased by 50% in the presence of 15.6 μM of sulfate and completely inhibited after loading with 171.9 μM of sulfate. 16S rRNA gene sequencing showed that the selenate-reducing bacteria decreased after the addition of sulfate. Metagenomic sequencing showed that the abundance of genes encoding molybdenum (Mo)-dependent selenate reductase reduced by >50% when exposed to high concentrations of sulfate. Furthermore, the decrease in the total genes encoding all Mo-oxidoreductases was much greater than that of the genes encoding molybdate transporters, suggesting that the inhibition of selenate reduction by sulfate was most likely via the direct competition with molybdate for the transport system, leading to a lack of available Mo for Mo-dependent selenate reductases and thus reducing their activities. This result was confirmed by a batch test wherein the supplementation of molybdate mitigated the sulfate effect. Overall, this study shed light on the underlying mechanism of sulfate inhibition on selenate reduction and laid the foundation for applying the technology to practical wastewaters.
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Affiliation(s)
- Ling-Dong Shi
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China
| | - Pan-Long Lv
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China
| | - Zi-Fan Niu
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China
| | - Chun-Yu Lai
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China
| | - He-Ping Zhao
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China.
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Chen C, Tian J, Zhou J, Ni X, Lei J, Wang X. Bacterial growth, morphology, and cell component changes in Herbaspirillum
sp. WT00C exposed to high concentration of selenate. J Basic Microbiol 2020; 60:304-321. [DOI: 10.1002/jobm.201900586] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 11/29/2019] [Accepted: 12/08/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Changmei Chen
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Faculty of Life Science; Hubei University; Wuhan China
| | - Jinbao Tian
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Faculty of Life Science; Hubei University; Wuhan China
| | - Jiahui Zhou
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Faculty of Life Science; Hubei University; Wuhan China
| | - Xuechen Ni
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Faculty of Life Science; Hubei University; Wuhan China
| | - Jia Lei
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Faculty of Life Science; Hubei University; Wuhan China
| | - Xingguo Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Faculty of Life Science; Hubei University; Wuhan China
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Shi LD, Wang M, Li ZY, Lai CY, Zhao HP. Dissolved oxygen has no inhibition on methane oxidation coupled to selenate reduction in a membrane biofilm reactor. CHEMOSPHERE 2019; 234:855-863. [PMID: 31252357 DOI: 10.1016/j.chemosphere.2019.06.138] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 06/02/2019] [Accepted: 06/18/2019] [Indexed: 06/09/2023]
Abstract
Methane oxidation coupled to selenate reduction has been suggested as a promising technology to bio-remediate selenium contaminated environments. However, the effect of dissolved oxygen (DO) on this process remained unclear. Here, we investigate the feasibility of selenate removal at two distinct DO concentrations. A membrane biofilm reactor (MBfR) was initially fed with ∼5 mg Se/L and then lowered to ∼1 mg Se/L of selenate, under anoxic condition containing ∼0.2 mg/L of influent DO. Selenate removal reached approximately 90% without selenite accumulation after one-month operation. Then 6-7 mg/L of DO was introduced and showed no apparent effect on selenate reduction in the subsequent operation. Electron microscopy suggested elevated oxygen exposure did not affect microbial shapes. 16S rDNA sequencing showed the aerobic methanotroph Methylocystis increased, while possible selenate reducers, Ignavibacterium and Bradyrhizobium, maintained stable after oxygen boost. Gene analysis indicated that nitrate/nitrite reductases positively correlated with selenate removal flux and were not remarkably affected by oxygen addition. Reversely, enzymes related with aerobic methane oxidation were obviously improved. This study provides a potential technology for selenate removal from oxygenated environments in a methane-based MBfR.
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Affiliation(s)
- Ling-Dong Shi
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China
| | - Min Wang
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China
| | - Zi-Yan Li
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China
| | - Chun-Yu Lai
- Advanced Water Management Centre, The University of Queensland, St. Lucia, Queensland, 4072, Australia
| | - He-Ping Zhao
- MOE Key Lab of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou, 310058, China; Zhejiang Prov Key Lab Water Pollut Control & Envi, Zhejiang University, Hangzhou, Zhejiang, China.
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12
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Wadgaonkar SL, Nancharaiah YV, Jacob C, Esposito G, Lens PNL. Microbial transformation of Se oxyanions in cultures of Delftia lacustris grown under aerobic conditions. J Microbiol 2019; 57:362-371. [PMID: 30900147 DOI: 10.1007/s12275-019-8427-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/20/2018] [Accepted: 11/26/2018] [Indexed: 12/29/2022]
Abstract
Delftia lacustris is reported for the first time as a selenate and selenite reducing bacterium, capable of tolerating and growing in the presence of ≥ 100 mM selenate and 25 mM selenite. The selenate reduction profiles of D. lacustris were investigated by varying selenate concentration, inoculum size, concentration and source of organic electron donor in minimal salt medium. Interestingly, the bacterium was able to reduce both selenate and selenite under aerobic conditions. Although considerable removal of selenate was observed at all concentrations investigated, D. lacustris was able to completely reduce 0.1 mM selenate within 96 h using lactate as the carbon source. Around 62.2% unaccounted selenium (unidentified organo-selenium compounds), 10.9% elemental selenium and 26.9% selenite were determined in the medium after complete reduction of selenate. Studies of the enzymatic activity of the cell fractions show that the selenite/selenate reducing enzymes were intracellular and independent of NADPH availability. D. lacustris shows an unique metabolism of selenium oxyanions to form elemental selenium and possibly also selenium ester compounds, thus a potential candidate for the remediation of selenium-contaminated wastewaters in aerobic environments. This novel finding will advance the field of bioremediation of selenium-contaminated sites and selenium bio-recovery and the production of potentially beneficial organic and inorganic reactive selenium species.
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Affiliation(s)
| | - Yarlagadda V Nancharaiah
- Biofouling and Biofilm Processes Section of Water and Steam Chemistry Division, Bhabha Atomic Research Centre, 603 102, Kalpakkam, Tamil Nadu, India
- Homi Bhabha National Institute, Anushakti Nagar Complex, Mumbai, 400 094, India
| | - Claus Jacob
- Division of Bioorganic Chemistry, School of Pharmacy, Saarland University, Campus B2, Saarland, Germany
| | - Giovanni Esposito
- Department of Civil, Architectural and Environmental Engineering, University of Napoli "Federico II", 80125, Napoli, Italy
| | - Piet N L Lens
- UNESCO IHE Institute for water Education, Delft, DA 2601, The Netherlands
- National University of Ireland Galway, Galway, H91 TK33, Ireland
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Respiratory Selenite Reductase from Bacillus selenitireducens Strain MLS10. J Bacteriol 2019; 201:JB.00614-18. [PMID: 30642986 DOI: 10.1128/jb.00614-18] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 01/03/2019] [Indexed: 11/20/2022] Open
Abstract
The putative respiratory selenite [Se(IV)] reductase (Srr) from Bacillus selenitireducens MLS10 has been identified through a polyphasic approach involving genomics, proteomics, and enzymology. Nondenaturing gel assays were used to identify Srr in cell fractions, and the active band was shown to contain a single protein of 80 kDa. The protein was identified through liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a homolog of the catalytic subunit of polysulfide reductase (PsrA). It was found to be encoded as part of an operon that contains six genes that we designated srrE, srrA, srrB, srrC, srrD, and srrF SrrA is the catalytic subunit (80 kDa), with a twin-arginine translocation (TAT) leader sequence indicative of a periplasmic protein and one putative 4Fe-4S binding site. SrrB is a small subunit (17 kDa) with four putative 4Fe-4S binding sites, SrrC (43 kDa) is an anchoring subunit, and SrrD (24 kDa) is a chaperon protein. Both SrrE (38 kDa) and SrrF (45 kDa) were annotated as rhodanese domain-containing proteins. Phylogenetic analysis revealed that SrrA belonged to the PsrA/PhsA clade but that it did not define a distinct subgroup, based on the putative homologs that were subsequently identified from other known selenite-respiring bacteria (e.g., Desulfurispirillum indicum and Pyrobaculum aerophilum). The enzyme appeared to be specific for Se(IV), showing no activity with selenate, arsenate, or thiosulfate, with a Km of 145 ± 53 μM, a V max of 23 ± 2.5 μM min-1, and a k cat of 23 ± 2.68 s-1 These results further our understanding of the mechanisms of selenium biotransformation and its biogeochemical cycle.IMPORTANCE Selenium is an essential element for life, with Se(IV) reduction a key step in its biogeochemical cycle. This report identifies for the first time a dissimilatory Se(IV) reductase, Srr, from a known selenite-respiring bacterium, the haloalkalophilic Bacillus selenitireducens strain MLS10. The work extends the versatility of the complex iron-sulfur molybdoenzyme (CISM) superfamily in electron transfer involving chalcogen substrates with different redox potentials. Further, it underscores the importance of biochemical and enzymological approaches in establishing the functionality of these enzymes.
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Detoxification and reduction of selenite to elemental red selenium by Frankia. Antonie van Leeuwenhoek 2018; 112:127-139. [DOI: 10.1007/s10482-018-1196-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 11/02/2018] [Indexed: 12/25/2022]
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15
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Liu J, Taylor JC, Baldwin SA. Removal of selenate from brine using anaerobic bacteria and zero valent iron. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2018; 222:348-358. [PMID: 29870963 DOI: 10.1016/j.jenvman.2018.05.095] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 05/25/2018] [Accepted: 05/30/2018] [Indexed: 06/08/2023]
Abstract
The mining industry needs to treat large volumes of wastewater highly concentrated in chemical compounds that can adversely affect receiving environments. One promising method of treatment is the use of reverse osmosis to remove most of the dissolved salts. However, the resulting brine reject is a highly saline wastewater that needs further treatment to remove the toxic components, such as selenate, which is a chemical compound of great concern in coal-mining regions. Biological reduction and removal of dissolved selenium from a brine solution was achieved. Microorganisms were enriched from environmental samples collected from two mines, respectively, at different geographic locations through adaptive evolution in the laboratory. Batch treatment of typical brine was tested with two different enrichments with the addition of either of two chemical forms of iron, ferrous chloride or zero valent iron. Successful selenium removal in the presence of high nitrate and sulphate concentrations was achieved with a combination of enriched microorganisms from one particular site and the addition of zero-valent iron. The composition and metabolic potential of the enriched microorganisms revealed Clostridium, Sphaerochaeta, Synergistes and Desulfosporosinus species with the metabolic potential for selenate reduction through the YgfK enzymatic process associated with selenium detoxification.
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Affiliation(s)
- Jinshu Liu
- Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, B.C., Canada
| | - Jon C Taylor
- Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, B.C., Canada
| | - Susan A Baldwin
- Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, B.C., Canada.
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Goff J, Yee N. Tellurate enters Escherichia coli K-12 cells via the SulT-type sulfate transporter CysPUWA. FEMS Microbiol Lett 2018; 364:4597602. [PMID: 29126297 DOI: 10.1093/femsle/fnx241] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 11/04/2017] [Indexed: 11/14/2022] Open
Abstract
Soluble forms of tellurium are environmental contaminants that are toxic to microorganisms. While tellurite [Te(IV)] is a well-characterized antimicrobial agent, little is known about the interactions of tellurate [Te(VI)] with bacterial cells. In this study, we investigated the role of sulfate transporters in the uptake of tellurate in Escherichia coli K-12. Mutant strains carrying a deletion of the cysW gene in the CysPUWA sulfate transporter system accumulated less cellular tellurium and exhibited higher resistance to tellurate compared with the wild-type strain. Complementation of the mutation restored tellurate sensitivity and uptake. These results indicate that tellurate enters E. coli cells to cause toxic effects via the CysPUWA sulfate transporter.
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Harter E, Wagner EM, Zaiser A, Halecker S, Wagner M, Rychli K. Stress Survival Islet 2, Predominantly Present in Listeria monocytogenes Strains of Sequence Type 121, Is Involved in the Alkaline and Oxidative Stress Responses. Appl Environ Microbiol 2017; 83:e00827-17. [PMID: 28625982 PMCID: PMC5541211 DOI: 10.1128/aem.00827-17] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 06/02/2017] [Indexed: 11/20/2022] Open
Abstract
The foodborne pathogen Listeria monocytogenes is able to survive a variety of stress conditions leading to the colonization of different niches like the food processing environment. This study focuses on the hypervariable genetic hot spot lmo0443 to lmo0449 haboring three inserts: the stress survival islet 1 (SSI-1), the single-gene insert LMOf2365_0481, and two homologous genes of the nonpathogenic species Listeria innocua: lin0464, coding for a putative transcriptional regulator, and lin0465, encoding an intracellular PfpI protease. Our prevalence study revealed a different distribution of the inserts between human and food-associated isolates. The lin0464-lin0465 insert was predominantly found in food-associated strains of sequence type 121 (ST121). Functional characterization of this insert showed that the putative PfpI protease Lin0465 is involved in alkaline and oxidative stress responses but not in acidic, gastric, heat, cold, osmotic, and antibiotic stresses. In parallel, deletion of lin0464 decreased survival under alkaline and oxidative stresses. The expression of both genes increased significantly under oxidative stress conditions independently of the alternative sigma factor σB Furthermore, we showed that the expression of the protease gene lin0465 is regulated by the transcription factor lin0464 under stress conditions, suggesting that lin0464 and lin0465 form a functional unit. In conclusion, we identified a novel stress survival islet 2 (SSI-2), predominantly present in L. monocytogenes ST121 strains, beneficial for survival under alkaline and oxidative stresses, potentially supporting adaptation and persistence of L. monocytogenes in food processing environments.IMPORTANCEListeria monocytogenes strains of ST121 are known to persist for months and even years in food processing environments, thereby increasing the risk of food contamination and listeriosis. However, the molecular mechanism underlying this remarkable niche-specific adaptation is still unknown. Here, we demonstrate that the genomic islet SSI-2, predominantly present in L. monocytogenes ST121 strains, is beneficial for survival under alkaline and oxidative stress conditions, which are routinely encountered in food processing environments. Our findings suggest that SSI-2 is part of a diverse set of molecular determinants contributing to niche-specific adaptation and persistence of L. monocytogenes ST121 strains in food processing environments.
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Affiliation(s)
- Eva Harter
- Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Eva Maria Wagner
- Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Andreas Zaiser
- Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Sabrina Halecker
- Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Martin Wagner
- Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Kathrin Rychli
- Institute for Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine Vienna, Vienna, Austria
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18
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Biogenic selenium nanoparticles: current status and future prospects. Appl Microbiol Biotechnol 2016; 100:2555-66. [DOI: 10.1007/s00253-016-7300-7] [Citation(s) in RCA: 204] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 12/30/2015] [Accepted: 01/05/2016] [Indexed: 02/08/2023]
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Abstract
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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Affiliation(s)
- Y V Nancharaiah
- Environmental Engineering and Water Technology Department, UNESCO-IHE Institute for Water Education, Delft, The Netherlands Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam, Tamil Nadu, India
| | - P N L Lens
- Environmental Engineering and Water Technology Department, UNESCO-IHE Institute for Water Education, Delft, The Netherlands
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20
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Bertolini C, van Aerle R, Lampis S, Moore KA, Paszkiewicz K, Butler CS, Vallini G, van der Giezen M. Draft Genome Sequence of Stenotrophomonas maltophilia SeITE02, a Gammaproteobacterium Isolated from Selenite-Contaminated Mining Soil. GENOME ANNOUNCEMENTS 2014; 2:e00331-14. [PMID: 24812214 PMCID: PMC4014682 DOI: 10.1128/genomea.00331-14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 04/14/2014] [Indexed: 11/20/2022]
Abstract
Stenotrophomonas maltophilia strain SeITE02 was isolated from the rhizosphere of the selenium-hyperaccumulating legume Astragalus bisculcatus. In this report, we provide the 4.56-Mb draft genome sequence of S. maltophilia SeITE02, a gammaproteobacterium that can withstand high concentrations of selenite and reduce these to elemental selenium.
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Affiliation(s)
| | | | - Silvia Lampis
- Department of Biotechnology, University of Verona, Verona, Italy
| | - Karen A. Moore
- Biosciences, University of Exeter, Exeter, United Kingdom
| | | | | | - Giovanni Vallini
- Department of Biotechnology, University of Verona, Verona, Italy
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Pseudomonas seleniipraecipitans proteins potentially involved in selenite reduction. Curr Microbiol 2014; 69:69-74. [PMID: 24604150 DOI: 10.1007/s00284-014-0555-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 01/14/2014] [Indexed: 10/25/2022]
Abstract
Pseudomonas seleniipraecipitans grows in the presence of high levels of selenite and selenate and reduces both oxyanions to elemental selenium (Se(0)), a property that may make P. seleniipraecipitans useful as an inoculant for biobarriers designed to remove selenite or selenate from ground or surface waters. An earlier study showed that P. seleniipraecipitans nitrate reductase reduced selenate to Se(0), but failed to identify the protein(s) involved in selenite reduction. This study used ammonium sulfate precipitation, hydrophobic interaction chromatography, and native PAGE to isolate two electrophoretic gel regions, identified as bands A and B that showed selenite-reductase-activity. Proteomics was used to identify the proteins present in those regions. Glutathione reductase (GR) was detected in the A-band; based on this information, Saccharomyces cerevisiae GR, obtained from a commercial source, was evaluated and found to have selenite-reductase-activity, confirming that GR can reduce selenite to Se(0). Proteomics was also used to detect the proteins present in the B-band and thioredoxin reductase (ThxR) was detected as a B-band protein; based on this information, E. coli ThxR, obtained from a commercial source, was evaluated and found to have selenite-reductase-activity, confirming that ThxR can reduce selenite to elemental selenium. Thus, evidence presented in this study shows that S. cerevisiae GR and E. coli ThxR can reduce SeO3 (2-) to Se(0) and strongly suggests that P. seleniipraecipitans GR and ThxR can also reduce SeO3 (2-) to Se(0).
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Hunter WJ. A Rhizobium selenitireducens protein showing selenite reductase activity. Curr Microbiol 2013; 68:311-6. [PMID: 24474405 DOI: 10.1007/s00284-013-0474-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 08/28/2013] [Indexed: 10/26/2022]
Abstract
Biobarriers remove, via precipitation, the metalloid selenite (SeO₃⁻²) from groundwater; a process that involves the biological reduction of soluble SeO₃⁻² to insoluble elemental red selenium (Se⁰). The enzymes associated with this reduction process are poorly understood. In Rhizobium selenitireducens at least two enzymes are potentially involved; one, a nitrite reductase reduces SeO₃⁻² to Se⁰ but another protein may also be involved which is investigated in this study. Proteins from R. selenitireducens cells were precipitated with ammonium sulfate and run on native electrophoresis gels. When these gels were incubated with NADH and SeO₃⁻² a band of precipitated Se⁰ developed signifying the presence of a SeO₃⁻² reducing protein. Bands were cut from the gel and analyzed for peptides via LCMSMS. The amino acid sequences associated with the bands indicated the presence of an NADH:flavin oxidoreductase that resembles YP_001326930 from Sinorhizobium medicae. The protein is part of a protein family termed old-yellow-enzymes (OYE) that contain a flavin binding domain. OYE enzymes are often involved in protecting cells from oxidative stress and, due in part to an active site that has a highly accessible binding pocket, are generally active on a wide range of substrates. This report is the first of an OYE enzyme being involved in SeO₃⁻² reduction.
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Affiliation(s)
- W J Hunter
- United States Department of Agriculture-Agricultural Research Service, 2150-D Centre Avenue, Fort Collins, CO, 80526-8119, USA,
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Genetic evidence for a molybdopterin-containing tellurate reductase. Appl Environ Microbiol 2013; 79:3171-5. [PMID: 23475618 DOI: 10.1128/aem.03996-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genetic identity and cofactor composition of the bacterial tellurate reductase are currently unknown. In this study, we examined the requirement of molybdopterin biosynthesis and molybdate transporter genes for tellurate reduction in Escherichia coli K-12. The results show that mutants deleted of the moaA, moaB, moaE, or mog gene in the molybdopterin biosynthesis pathway lost the ability to reduce tellurate. Deletion of the modB or modC gene in the molybdate transport pathway also resulted in complete loss of tellurate reduction activity. Genetic complementation by the wild-type sequences restored tellurate reduction activity in the mutant strains. These findings provide genetic evidence that tellurate reduction in E. coli involves a molybdoenzyme.
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The prokaryotic Mo/W-bisPGD enzymes family: a catalytic workhorse in bioenergetic. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:1048-85. [PMID: 23376630 DOI: 10.1016/j.bbabio.2013.01.011] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 01/21/2013] [Accepted: 01/23/2013] [Indexed: 01/05/2023]
Abstract
Over the past two decades, prominent importance of molybdenum-containing enzymes in prokaryotes has been put forward by studies originating from different fields. Proteomic or bioinformatic studies underpinned that the list of molybdenum-containing enzymes is far from being complete with to date, more than fifty different enzymes involved in the biogeochemical nitrogen, carbon and sulfur cycles. In particular, the vast majority of prokaryotic molybdenum-containing enzymes belong to the so-called dimethylsulfoxide reductase family. Despite its extraordinary diversity, this family is characterized by the presence of a Mo/W-bis(pyranopterin guanosine dinucleotide) cofactor at the active site. This review highlights what has been learned about the properties of the catalytic site, the modular variation of the structural organization of these enzymes, and their interplay with the isoprenoid quinones. In the last part, this review provides an integrated view of how these enzymes contribute to the bioenergetics of prokaryotes. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
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Sevcenco AM, Hagen WR, Hagedoorn PL. Microbial Metalloproteomes Explored Using MIRAGE. Chem Biodivers 2012; 9:1967-80. [DOI: 10.1002/cbdv.201100412] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Abstract
SUMMARYPlasmodium falciparum has for some time been developing resistance against known anti-malarial drugs, and therefore a new drug is urgently needed. Selenium (Se), an essential trace element, in the form of inorganic Se, selenite (SeO32−), has been reported to have an anti-plasmodial effect, but its mechanism is still unclear. In the present study, we evaluated the anti-plasmodial effect of several Se compounds against P. falciparum in vitro. The anti-plasmodial effect of several Se compounds was analysed and their apoptosis-inducing activity was evaluated by morphological observation, DNA fragmentation assay and mitochondrial function analysis. SeO32−, methylseleninic acid, selenomethionine and selenocystine have anti-plasmodial effects with 50% inhibition concentration at 9, 10, 45, and 65 μm, respectively, while selenate and methylselenocysteine up to 100 μm have no effect on parasite growth. The effective Se compounds caused the parasites to become shrunken and pyknotic and significantly increased mitochondrial damage against P. falciparum compared to the untreated control. In conclusion, SeO32−, methylseleninic acid, selenomethionine and selenocystine have anti-plasmodial activities that induce apoptosis-like cell death in P. falciparum, and the anti-plasmodial effects of Se seem to be based on its chemical forms. The apoptosis-like cell-death mechanism in P. falciparum can be beneficial to respond to the growing problem of drug resistance.
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Molecular cloning and characterization of the srdBCA operon, encoding the respiratory selenate reductase complex, from the selenate-reducing bacterium Bacillus selenatarsenatis SF-1. J Bacteriol 2011; 193:2141-8. [PMID: 21357486 DOI: 10.1128/jb.01197-10] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, we isolated a selenate- and arsenate-reducing bacterium, designated strain SF-1, from selenium-contaminated sediment and identified it as a novel species, Bacillus selenatarsenatis. B. selenatarsenatis strain SF-1 independently reduces selenate to selenite, arsenate to arsenite, and nitrate to nitrite by anaerobic respiration. To identify the genes involved in selenate reduction, 17 selenate reduction-defective mutant strains were isolated from a mutant library generated by random insertion of transposon Tn916. Tn916 was inserted into the same genome position in eight mutants, and the representative strain SF-1AM4 did not reduce selenate but did reduce nitrate and arsenate to the same extent as the wild-type strain. The disrupted gene was located in an operon composed of three genes designated srdBCA, which were predicted to encode a putative oxidoreductase complex by the BLASTX program. The plasmid vector pGEMsrdBCA, containing the srdBCA operon with its own promoter, conferred the phenotype of selenate reduction in Escherichia coli DH5α, although E. coli strains containing plasmids lacking any one or two of the open reading frames from srdBCA did not exhibit the selenate-reducing phenotype. Domain structure analysis of the deduced amino acid sequence revealed that SrdBCA had typical features of membrane-bound and molybdopterin-containing oxidoreductases. It was therefore proposed that the srdBCA operon encoded a respiratory selenate reductase complex. This is the first report of genes encoding selenate reductase in gram-positive bacteria.
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Aguilar-Barajas E, Díaz-Pérez C, Ramírez-Díaz MI, Riveros-Rosas H, Cervantes C. Bacterial transport of sulfate, molybdate, and related oxyanions. Biometals 2011; 24:687-707. [PMID: 21301930 DOI: 10.1007/s10534-011-9421-x] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 01/26/2011] [Indexed: 12/29/2022]
Affiliation(s)
- Esther Aguilar-Barajas
- Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana, Edificio B-3, Ciudad Universitaria, 58030 Morelia, Michoacan, Mexico
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Sakaguchi T, Nakano T, Kimura Y, Nogami S, Kubo I, Morita Y. Development of a genetic transfer system in selenate-respiring bacterium Citrobacter sp. strain JSA which was isolated from natural freshwater sediment. J Biosci Bioeng 2011; 111:443-7. [PMID: 21215694 DOI: 10.1016/j.jbiosc.2010.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 10/25/2010] [Accepted: 12/01/2010] [Indexed: 11/16/2022]
Abstract
Conjugative mating between the selenate-reducing bacterium Citrobacter sp. strain JSA and Escherichia coli S17-1 harboring the broad-host-range plasmid pKT230 or pKT240 (IncQ) allowed genetic transfer to strain JSA at a maximum frequency of 2.5×10(-5) (pKT230) and 5.1×10(-6) (pKT240) per recipient JSA cell. Kanamycin-resistant (selection marker of pKT230 and pKT240) transconjugants were routinely obtained with this method, and we confirmed that both vectors were also successfully transferred and replicated in strain JSA without alteration of the replicon. Furthermore, an electroporation method has also allowed transformation of JSA at a frequency of 10(-7) to 10(-6) transformants per μg vector DNA (per recipient cell), and PCR and hybridization analyses revealed that pKT230 and pKT240 are stably maintained in transformed JSA cells. These results indicated that both InQ plasmids can be used as vectors for gene transfer to selenate-reducing strain JSA. This is the first study to demonstrate an effective method for genetic transfer in a selenate-reducing Citrobacter bacterium and will aid in the elucidation of the selenium oxyanion reduction mechanism in this genus of environmental selenate-respiring isolates.
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Affiliation(s)
- Toshifumi Sakaguchi
- Department of Environmental Sciences, Prefectural University of Hiroshima, Hiroshima 727-0023, Japan.
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Sevcenco AM, Pinkse MWH, Wolterbeek HT, Verhaert PDEM, Hagen WR, Hagedoorn PL. Exploring the microbial metalloproteome using MIRAGE. Metallomics 2011; 3:1324-30. [DOI: 10.1039/c1mt00154j] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Jasenec A, Barasa N, Kulkarni S, Shaik N, Moparthi S, Konda V, Caguiat J. Proteomic profiling of L-cysteine induced selenite resistance in Enterobacter sp. YSU. Proteome Sci 2009; 7:30. [PMID: 19715574 PMCID: PMC2744661 DOI: 10.1186/1477-5956-7-30] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 08/28/2009] [Indexed: 11/10/2022] Open
Abstract
Background Enterobacter sp. YSU is resistant to several different heavy metal salts, including selenite. A previous study using M-9 minimal medium showed that when the selenite concentration was 100,000 times higher than the sulfate concentration, selenite entered Escherichia coli cells using two pathways: a specific and a non-specific pathway. In the specific pathway, selenite entered the cells through a yet to be characterized channel dedicated for selenite. In the non-specific pathway, selenite entered the cells through a sulfate permease channel. Addition of L-cystine, an L-cysteine dimer, appeared to indirectly decrease selenite import into the cell through the non-specific pathway. However, it did not affect the level of selenite transport into the cell through the specific pathway. Results Growth curves using M-9 minimal medium containing 40 mM selenite and 1 mM sulfate showed that Enterobacter sp. YSU grew when L-cysteine was present but died when it was absent. Differential protein expression analysis by two dimensional gel electrophoresis showed that CysK was present in cultures containing selenite and lacking L-cysteine but absent in cultures containing both selenite and L-cysteine. Additional RT-PCR studies demonstrated that transcripts for the sulfate permease genes, cysA, cysT and cysW, were down-regulated in the presence of L-cysteine. Conclusion L-cysteine appeared to confer selenite resistance upon Enterobacter sp. YSU by decreasing the level of selenite transport into the cell through the non-specific pathway.
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Affiliation(s)
- Ashley Jasenec
- Department of Biological Sciences, Youngstown State University, OH 44555, USA.
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Guymer D, Maillard J, Sargent F. A genetic analysis of in vivo selenate reduction by Salmonella enterica serovar Typhimurium LT2 and Escherichia coli K12. Arch Microbiol 2009; 191:519-28. [DOI: 10.1007/s00203-009-0478-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 04/01/2009] [Accepted: 04/06/2009] [Indexed: 11/28/2022]
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Sakaguchi T, Kato M, Kuriyama N, Niiyama H, Hamada S, Morita Y, Tamiya E. Conjugal Transformation and Transposon and Chemical Mutagenesis of Gram-Negative Selenate-Respiring Citrobacter sp. Strain JSA. Curr Microbiol 2009; 59:88-94. [DOI: 10.1007/s00284-009-9406-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 03/19/2009] [Accepted: 03/23/2009] [Indexed: 11/29/2022]
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Ma J, Kobayashi DY, Yee N. Role of menaquinone biosynthesis genes in selenate reduction byEnterobacter cloacaeSLD1a-1 andEscherichia coliK12. Environ Microbiol 2009; 11:149-58. [DOI: 10.1111/j.1462-2920.2008.01749.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Lenz M, Janzen N, Lens PNL. Selenium oxyanion inhibition of hydrogenotrophic and acetoclastic methanogenesis. CHEMOSPHERE 2008; 73:383-388. [PMID: 18653211 DOI: 10.1016/j.chemosphere.2008.05.059] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 05/08/2008] [Accepted: 05/18/2008] [Indexed: 05/26/2023]
Abstract
Inhibitory effects of selenite and selenate towards hydrogenotrophic and acetoclastic methanogenesis were evaluated in anaerobic toxicity assays. The 50% inhibitory concentration (IC50) of both selenium oxyanions was below 6.1x10(-5)M in hydrogenotrophic assays, whereas acetoclastic methanogens were less inhibited: IC50=8.3x10(-5)M and 5.5x10(-4)M for selenite and selenate, respectively. Selenite completely inhibits methanogenesis from both substrates tested at concentrations > or =10(-3)M selenite, while only marginal methanogenic activities occur at equimolar concentrations of selenate. Selenite becomes irreversibly inhibitory upon a single exposure, whereas selenate inhibits methanogens upon repeated exposure. Consequently, methane recovery can be seriously hampered or even impossible during anaerobic treatment of highly selenium contaminated waste streams.
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Affiliation(s)
- Markus Lenz
- Sub-Department of Environmental Technology, Wageningen University, 6700 EV Wageningen, The Netherlands
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Haft DH, Self WT. Orphan SelD proteins and selenium-dependent molybdenum hydroxylases. Biol Direct 2008; 3:4. [PMID: 18289380 PMCID: PMC2276186 DOI: 10.1186/1745-6150-3-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Accepted: 02/20/2008] [Indexed: 11/24/2022] Open
Abstract
Bacterial and Archaeal cells use selenium structurally in selenouridine-modified tRNAs, in proteins translated with selenocysteine, and in the selenium-dependent molybdenum hydroxylases (SDMH). The first two uses both require the selenophosphate synthetase gene, selD. Examining over 500 complete prokaryotic genomes finds selD in exactly two species lacking both the selenocysteine and selenouridine systems, Enterococcus faecalis and Haloarcula marismortui. Surrounding these orphan selD genes, forming bidirectional best hits between species, and detectable by Partial Phylogenetic Profiling vs. selD, are several candidate molybdenum hydroxylase subunits and accessory proteins. We propose that certain accessory proteins, and orphan selD itself, are markers through which new selenium-dependent molybdenum hydroxylases can be found.
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Affiliation(s)
- Daniel H Haft
- Department of Bioinformatics, J, Craig Venter Institute, Rockville, MD 20850, USA.
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Kenyon WJ, Nicholson KL, Rezuchova B, Homerova D, Garcia-Del Portillo F, Finlay BB, Pallen MJ, Kormanec J, Spector MP. Sigma(s)-Dependent carbon-starvation induction of pbpG (PBP 7) is required for the starvation-stress response in Salmonella enterica serovar Typhimurium. MICROBIOLOGY-SGM 2007; 153:2148-2158. [PMID: 17600059 DOI: 10.1099/mic.0.2007/005199-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Carbon-energy source starvation is a commonly encountered stress that can influence the epidemiology and virulence of Salmonella enterica serovars. Salmonella responds to C-starvation by eliciting the starvation-stress response (SSR), which allows for long-term C-starvation survival and cross-resistance to other stresses. The stiC locus was identified as a C-starvation-inducible, sigma(S)-dependent locus required for a maximal SSR. We report here that the stiC locus is an operon composed of the yohC (putative transport protein) and pbpG (penicillin-binding protein-7/8) genes. yohC pbpG transcription is initiated from a sigma(S)-dependent C-starvation-inducible promoter upstream of yohC. Another (sigma(S)-independent) promoter, upstream of pbpG, drives lower constitutive pbpG transcription, primarily during exponential phase. C-starvation-inducible pbpG expression was required for development of the SSR in 5 h, but not 24 h, C-starved cells; yohC was dispensable for the SSR. Furthermore, the yohC pbpG operon is induced within MDCK epithelial cells, but was not essential for oral virulence in BALB/c mice. Thus, PBP 7 is required for physiological changes, occurring within the first few hours of C-starvation, essential for the development of the SSR. Lack of PBP 7, however, can be compensated for by further physiological changes developed in 24 h C-starved cells. This supports the dynamic overlapping and distinct nature of resistance pathways within the Salmonella SSR.
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Affiliation(s)
- William J Kenyon
- Department of Biomedical Sciences, University of South Alabama, Mobile, AL 36688, USA
| | - Kristy L Nicholson
- Department of Biomedical Sciences, University of South Alabama, Mobile, AL 36688, USA
| | - Bronislava Rezuchova
- Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, 845 51 Bratislava 45, Slovak Republic
| | - Dagmar Homerova
- Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, 845 51 Bratislava 45, Slovak Republic
| | - Francisco Garcia-Del Portillo
- The University of British Columbia, Michael Smith Laboratories, 301-2185 East Mall, Vancouver, BC, Canada V6T 1Z4
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología-CSIC, C/ Darwin 3, 28049 Madrid, Spain
| | - B Brett Finlay
- The University of British Columbia, Michael Smith Laboratories, 301-2185 East Mall, Vancouver, BC, Canada V6T 1Z4
| | - Mark J Pallen
- Division of Immunity and Infection, Medical School, University of Birmingham, Birmingham B15 2TT, UK
| | - Jan Kormanec
- Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, 845 51 Bratislava 45, Slovak Republic
| | - Michael P Spector
- Department of Biomedical Sciences, University of South Alabama, Mobile, AL 36688, USA
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Abstract
This review describes volatiles released into the air by bacteria growing on defined media. Their occurrence, function, and biosynthesis are discussed, and a total of 308 references are cited. An effort has been made to organize the compounds according to their biosynthetic origin.
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Affiliation(s)
- Stefan Schulz
- Institute of Organic Chemistry, Technical University of Braunschweig, Hagenring 30, 38106, Braunschweig, Germany.
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Yee N, Ma J, Dalia A, Boonfueng T, Kobayashi DY. Se(VI) reduction and the precipitation of Se(0) by the facultative bacterium Enterobacter cloacae SLD1a-1 are regulated by FNR. Appl Environ Microbiol 2007; 73:1914-20. [PMID: 17261520 PMCID: PMC1828800 DOI: 10.1128/aem.02542-06] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fate of selenium in the environment is controlled, in part, by microbial selenium oxyanion reduction and Se(0) precipitation. In this study, we identified a genetic regulator that controls selenate reductase activity in the Se-reducing bacterium Enterobacter cloacae SLD1a-1. Heterologous expression of the global anaerobic regulatory gene fnr (fumarate nitrate reduction regulator) from E. cloacae in the non-Se-reducing strain Escherichia coli S17-1 activated the ability to reduce Se(VI) and precipitate insoluble Se(0) particles. Se(VI) reduction by E. coli S17-1 containing the fnr gene occurred at rates similar to those for E. cloacae, with first-order reaction constants of k = 2.07 x 10(-2) h(-1) and k = 3.36 x 10(-2) h(-1), respectively, and produced elemental selenium particles with identical morphologies and short-range atomic orders. Mutation of the fnr gene in E. cloacae SLD1a-1 resulted in derivative strains that were deficient in selenate reductase activity and unable to precipitate elemental selenium. Complementation by the wild-type fnr sequence restored the ability of mutant strains to reduce Se(VI). Our findings suggest that Se(VI) reduction and the precipitation of Se(0) by facultative anaerobes are regulated by oxygen-sensing transcription factors and occur under suboxic conditions.
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Affiliation(s)
- N Yee
- Department of Environmental Sciences, Rutgers University, 14 College Farm Rd., New Brunswick, NJ 07102, USA.
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Ridley H, Watts CA, Richardson DJ, Butler CS. Resolution of distinct membrane-bound enzymes from Enterobacter cloacae SLD1a-1 that are responsible for selective reduction of nitrate and selenate oxyanions. Appl Environ Microbiol 2006; 72:5173-80. [PMID: 16885262 PMCID: PMC1538730 DOI: 10.1128/aem.00568-06] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterobacter cloacae SLD1a-1 is capable of reductive detoxification of selenate to elemental selenium under aerobic growth conditions. The initial reductive step is the two-electron reduction of selenate to selenite and is catalyzed by a molybdenum-dependent enzyme demonstrated previously to be located in the cytoplasmic membrane, with its active site facing the periplasmic compartment (C. A. Watts, H. Ridley, K. L. Condie, J. T. Leaver, D. J. Richardson, and C. S. Butler, FEMS Microbiol. Lett. 228:273-279, 2003). This study describes the purification of two distinct membrane-bound enzymes that reduce either nitrate or selenate oxyanions. The nitrate reductase is typical of the NAR-type family, with alpha and beta subunits of 140 kDa and 58 kDa, respectively. It is expressed predominantly under anaerobic conditions in the presence of nitrate, and while it readily reduces chlorate, it displays no selenate reductase activity in vitro. The selenate reductase is expressed under aerobic conditions and expressed poorly during anaerobic growth on nitrate. The enzyme is a heterotrimeric (alphabetagamma) complex with an apparent molecular mass of approximately 600 kDa. The individual subunit sizes are approximately 100 kDa (alpha), approximately 55 kDa (beta), and approximately 36 kDa (gamma), with a predicted overall subunit composition of alpha3beta3gamma3. The selenate reductase contains molybdenum, heme, and nonheme iron as prosthetic constituents. Electronic absorption spectroscopy reveals the presence of a b-type cytochrome in the active complex. The apparent Km for selenate was determined to be approximately 2 mM, with an observed Vmax of 500 nmol SeO4(2-) min(-1) mg(-1) (kcat, approximately 5.0 s(-1)). The enzyme also displays activity towards chlorate and bromate but has no nitrate reductase activity. These studies report the first purification and characterization of a membrane-bound selenate reductase.
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Affiliation(s)
- Helen Ridley
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom
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42
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Rollins DK, Zhai D, Joe AL, Guidarelli JW, Murarka A, Gonzalez R. A novel data mining method to identify assay-specific signatures in functional genomic studies. BMC Bioinformatics 2006; 7:377. [PMID: 16907975 PMCID: PMC1599756 DOI: 10.1186/1471-2105-7-377] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2006] [Accepted: 08/14/2006] [Indexed: 11/25/2022] Open
Abstract
Background: The highly dimensional data produced by functional genomic (FG) studies makes it difficult to visualize relationships between gene products and experimental conditions (i.e., assays). Although dimensionality reduction methods such as principal component analysis (PCA) have been very useful, their application to identify assay-specific signatures has been limited by the lack of appropriate methodologies. This article proposes a new and powerful PCA-based method for the identification of assay-specific gene signatures in FG studies. Results: The proposed method (PM) is unique for several reasons. First, it is the only one, to our knowledge, that uses gene contribution, a product of the loading and expression level, to obtain assay signatures. The PM develops and exploits two types of assay-specific contribution plots, which are new to the application of PCA in the FG area. The first type plots the assay-specific gene contribution against the given order of the genes and reveals variations in distribution between assay-specific gene signatures as well as outliers within assay groups indicating the degree of importance of the most dominant genes. The second type plots the contribution of each gene in ascending or descending order against a constantly increasing index. This type of plots reveals assay-specific gene signatures defined by the inflection points in the curve. In addition, sharp regions within the signature define the genes that contribute the most to the signature. We proposed and used the curvature as an appropriate metric to characterize these sharp regions, thus identifying the subset of genes contributing the most to the signature. Finally, the PM uses the full dataset to determine the final gene signature, thus eliminating the chance of gene exclusion by poor screening in earlier steps. The strengths of the PM are demonstrated using a simulation study, and two studies of real DNA microarray data – a study of classification of human tissue samples and a study of E. coli cultures with different medium formulations. Conclusion We have developed a PCA-based method that effectively identifies assay-specific signatures in ranked groups of genes from the full data set in a more efficient and simplistic procedure than current approaches. Although this work demonstrates the ability of the PM to identify assay-specific signatures in DNA microarray experiments, this approach could be useful in areas such as proteomics and metabolomics.
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Affiliation(s)
- Derrick K Rollins
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, USA
- Department of Statistics, Iowa State University, Ames, Iowa 50011, USA
| | - Dongmei Zhai
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, USA
- Department of Statistics, Iowa State University, Ames, Iowa 50011, USA
| | - Alrica L Joe
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - Jack W Guidarelli
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - Abhishek Murarka
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77251-1892, USA
| | - Ramon Gonzalez
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, USA
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77251-1892, USA
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Pierru B, Grosse S, Pignol D, Sabaty M. Genetic and biochemical evidence for the involvement of a molybdenum-dependent enzyme in one of the selenite reduction pathways of Rhodobacter sphaeroides f. sp. denitrificans IL106. Appl Environ Microbiol 2006; 72:3147-53. [PMID: 16672451 PMCID: PMC1472318 DOI: 10.1128/aem.72.5.3147-3153.2006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Selenite reduction in Rhodobacter sphaeroides f. sp. denitrificans was observed under photosynthetic conditions, following a 100-h lag period. This adaptation period was suppressed if the medium was inoculated with a culture previously grown in the presence of selenite, suggesting that selenite reduction involves an inducible enzymatic pathway. A transposon library was screened to isolate mutants affected in selenite reduction. Of the eight mutants isolated, two were affected in molybdenum cofactor synthesis. These moaA and mogA mutants showed an increased duration of the lag phase and a decreased rate of selenite reduction. When grown in the presence of tungstate, a well-known molybdenum-dependent enzyme (molybdoenzyme) inhibitor, the wild-type strain displayed the same phenotype. The addition of tungstate in the medium or the inactivation of the molybdocofactor synthesis induced a decrease of 40% in the rate of selenite reduction. These results suggest that several pathways are involved and that one of them involves a molybdoenzyme. Although addition of nitrate or dimethyl sulfoxide (DMSO) to the medium increased the selenite reduction activity of the culture, neither the periplasmic nitrate reductase NAP nor the DMSO reductase is the implicated molybdoenzyme, since the napA and dmsA mutants, with expression of nitrate reductase and DMSO reductase, respectively, eliminated, were not affected by selenite reduction. A role for the biotine sulfoxide reductase, another characterized molybdoenzyme, is unlikely, since its overexpression in a defective strain did not restore the selenite reduction activity.
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Affiliation(s)
- Bénédicte Pierru
- Laboratoire de Bioénergétique Cellulaire, CEA/Cadarache, DSV-DEVM, 13108 St. Paul lez Durance Cedex, France
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44
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Zawadzka AM, Crawford RL, Paszczynski AJ. Pyridine-2,6-bis(thiocarboxylic acid) produced by Pseudomonas stutzeri KC reduces and precipitates selenium and tellurium oxyanions. Appl Environ Microbiol 2006; 72:3119-29. [PMID: 16672449 PMCID: PMC1472348 DOI: 10.1128/aem.72.5.3119-3129.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The siderophore of Pseudomonas stutzeri KC, pyridine-2,6-bis(thiocarboxylic acid) (pdtc), is shown to detoxify selenium and tellurium oxyanions in bacterial cultures. A mechanism for pdtc's detoxification of tellurite and selenite is proposed. The mechanism is based upon determination using mass spectrometry and energy-dispersive X-ray spectrometry of the chemical structures of compounds formed during initial reactions of tellurite and selenite with pdtc. Selenite and tellurite are reduced by pdtc or its hydrolysis product H(2)S, forming zero-valent pdtc selenides and pdtc tellurides that precipitate from solution. These insoluble compounds then hydrolyze, releasing nanometer-sized particles of elemental selenium or tellurium. Electron microscopy studies showed both extracellular precipitation and internal deposition of these metalloids by bacterial cells. The precipitates formed with synthetic pdtc were similar to those formed in pdtc-producing cultures of P. stutzeri KC. Culture filtrates of P. stutzeri KC containing pdtc were also active in removing selenite and precipitating elemental selenium and tellurium. The pdtc-producing wild-type strain KC conferred higher tolerance against selenite and tellurite toxicity than a pdtc-negative mutant strain, CTN1. These observations support the hypothesis that pdtc not only functions as a siderophore but also is involved in an initial line of defense against toxicity from various metals and metalloids.
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Affiliation(s)
- Anna M Zawadzka
- Environmental Biotechnology Institute, University of Idaho, Food Research Center 103, P.O. Box 441052, Moscow, ID 83844-1052, USA
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45
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Hunter WJ, Kuykendall LD. Identification and characterization of an Aeromonas salmonicida (syn Haemophilus piscium) strain that reduces selenite to elemental red selenium. Curr Microbiol 2006; 52:305-9. [PMID: 16550462 DOI: 10.1007/s00284-005-0303-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Accepted: 10/12/2005] [Indexed: 11/30/2022]
Abstract
A bacterium that reduces toxic and mobile selenite to insoluble elemental selenium (Se0) was isolated from a laboratory scale permeable reactive biobarrier. Biochemical tests and 16S rRNA gene sequence alignment identified the isolate as Aeromonas salmonicida. Two colony types were isolated, one more resistant to selenite than the other. Both grew on agar plates containing 16 mM: selenite, although the colony diameter was reduced to 8% of controls with the small colony type and to 18% with the large colony type. Further study was done with the large colony type. In anaerobic culture, this bacterium was able to use nitrate as a term electron acceptor but not selenate or selenite. In aerobic culture, when no nitrate was present, early log phase cells removed selenite at a rate of 2.6 +/- 0.42 micromol SeO3 (-2)/mg protein/day. Reduction was retarded by 25 mM: nitrate. Mutants with a diminished ability to reduce selenite to Se0 also had a reduced ability to reduce nitrate to nitrous oxide. This bacterium, or perhaps its enzymes or DNA, might be used to remove selenite from contaminated groundwaters.
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Affiliation(s)
- William J Hunter
- USDA-ARS, 2150-D Centre Avenue, Fort Collins, CO, 80526-8119, USA.
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46
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Chung J, Nerenberg R, Rittmann BE. Bioreduction of selenate using a hydrogen-based membrane biofilm reactor. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2006; 40:1664-71. [PMID: 16568785 DOI: 10.1021/es051251g] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A H2-based, denitrifying and sulfate-reducing membrane-biofilm reactor (MBfR) was shown to be effective for removing selenate (Se(VI)) from water or wastewater by reducing it to insoluble Se(0). When Se(VI) was first added to the MBfR, Se(VI) reduction--first to selenite (Se(IV)) and then mostly to Se(0)--took place immediately and then increased over three weeks, suggesting enrichment for dissimilatory selenium-reducing bacteria. Increasing the H2 pressure improved the Se(VI) reduction rate and total-Se removal, and lowering the influent Se(VI) concentration from 1000 to 260 microg Se/L increased the average Se removal to 94%, which corresponded to an effluent Se concentration of less than 12 microg Se/L, a value well below the standard of 50 microg Se/L. The fact that the effluent suspended solids contained reduced Se suggests that Se(0) was retained in the biofilm, which detached to form the effluent suspended solids. A series of short-term experiments elaborated on how decreased influent selenate loading and increased H2 pressure could systematically improve the reduction of Se(VI) and removal of total Se. Short-term experiments also demonstrated that selenate reduction improved with lower influent nitrate concentration, suggesting that H2 was more available for selenate reduction when the H2 demand for denitrification was smaller. Complete sulfate reduction, which occurred in parallel to nitrate reduction, dominated the electron-equivalent flux. Like selenate reduction, but unlike nitrate reduction, sulfate reduction was sensitive to H2 pressure and appeared to be inhibited by selenate. Finally, selenate reduction was relatively insensitive to pH in the range of 7.0 to 9.0. This research shows that the MBfR can be effective for removing Se(VI) in water or wastewater to below the 50 microg Se/L standard.
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Affiliation(s)
- Jinwook Chung
- Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3109, USA.
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Tao H, Hasona A, Do PM, Ingram LO, Shanmugam KT. Global gene expression analysis revealed an unsuspected deo operon under the control of molybdate sensor, ModE protein, in Escherichia coli. Arch Microbiol 2005; 184:225-33. [PMID: 16205910 DOI: 10.1007/s00203-005-0039-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2005] [Revised: 08/30/2005] [Accepted: 09/02/2005] [Indexed: 10/25/2022]
Abstract
ModE protein, a molybdate sensor/regulator, controls the transcription of genes coding for molybdate uptake (mod), molybdopterin synthesis (moa), molybdoenzymes nitrate reductase (nap) and dimethylsulfoxide reductase (dms), as well as fermentative dihydrogen production (fdhF and hyc) and respiratory nitrate reductase (narXL) in Escherichia coli. The catalytic product of a second protein, MoeA, is also required for molybdate-dependent positive regulation of hyc and nar operons. To explore the potential role of ModE and MoeA in the regulation of other E. coli genes, the global gene expression profile of a wild type and a modE, moeA double mutant grown in glucose-minimal medium under anaerobic conditions were compared. Expression of 67 genes was affected by the modE and moeA mutations (P value <0.01). Of these, 17 differed by at least 2-fold or higher. Fourteen genes were expressed at a higher level in the mutant (2.4- to 23.9-fold) (notably, mod-molybdate transport, deo-nucleoside catabolism and opp-oligopeptide transport operons) and dmsA and yli operon were expressed at a higher level in the wild type parent (2.6- to 5.7-fold). One of the unexpected findings was repression of the deo operon by ModE. This was confirmed by quantitative RT-PCR and by the analysis of a deoC-lacZ fusion. The deo promoter/operator region contains a putative ModE-consensus sequence centered at -35 in which the adenines are replaced by guanines (TGTGT-N7-TGTGT). The ModE protein did bind to the deo upstream DNA and shifted its electrophoretic mobility. Bioinformatics analysis of the E. coli genome for ModE-consensus motif (TATAT-N7-TAYAT) identified 21 additional genes/operons including the moa as potential targets for Mo-control. The physiological role of many of the genes identified solely by bioinformatics (19/21) is unknown. Expression levels of these genes were similar in the parent and the isogenic modE, moeA mutant when cultured anaerobically in glucose-minimal medium. This study identified additional targets, such as deo and opp, for the Mo-dependent control in E. coli.
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Affiliation(s)
- Han Tao
- Department of Microbiology and Cell Science, University of Florida, Box 110700, Gainesville, FL 32611, USA
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48
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Sarret G, Avoscan L, Carrière M, Collins R, Geoffroy N, Carrot F, Covès J, Gouget B. Chemical forms of selenium in the metal-resistant bacterium Ralstonia metallidurans CH34 exposed to selenite and selenate. Appl Environ Microbiol 2005; 71:2331-7. [PMID: 15870319 PMCID: PMC1087582 DOI: 10.1128/aem.71.5.2331-2337.2005] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ralstonia metallidurans CH34, a soil bacterium resistant to a variety of metals, is known to reduce selenite to intracellular granules of elemental selenium (Se(0)). We have studied the kinetics of selenite (Se(IV)) and selenate (Se(VI)) accumulation and used X-ray absorption spectroscopy to identify the accumulated form of selenate, as well as possible chemical intermediates during the transformation of these two oxyanions. When introduced during the lag phase, the presence of selenite increased the duration of this phase, as previously observed. Selenite introduction was followed by a period of slow uptake, during which the bacteria contained Se(0) and alkyl selenide in equivalent proportions. This suggests that two reactions with similar kinetics take place: an assimilatory pathway leading to alkyl selenide and a slow detoxification pathway leading to Se(0). Subsequently, selenite uptake strongly increased (up to 340 mg Se per g of proteins) and Se(0) was the predominant transformation product, suggesting an activation of selenite transport and reduction systems after several hours of contact. Exposure to selenate did not induce an increase in the lag phase duration, and the bacteria accumulated approximately 25-fold less Se than when exposed to selenite. Se(IV) was detected as a transient species in the first 12 h after selenate introduction, Se(0) also occurred as a minor species, and the major accumulated form was alkyl selenide. Thus, in the present experimental conditions, selenate mostly follows an assimilatory pathway and the reduction pathway is not activated upon selenate exposure. These results show that R. metallidurans CH34 may be suitable for the remediation of selenite-, but not selenate-, contaminated environments.
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Affiliation(s)
- Géraldine Sarret
- Environmental Geochemistry Group, LGIT, University of Grenoble and CNRS, BP 53, 38041 Grenoble, Cedex 9, France.
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49
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Ledgham F, Quest B, Vallaeys T, Mergeay M, Covès J. A probable link between the DedA protein and resistance to selenite. Res Microbiol 2005; 156:367-74. [PMID: 15808941 DOI: 10.1016/j.resmic.2004.11.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 11/22/2004] [Accepted: 11/24/2004] [Indexed: 10/26/2022]
Abstract
To understand the molecular events involved in the reduction of selenite to non-toxic elemental selenium, 4000 clones of Ralstonia metallidurans CH34 were produced by random Tn5 transposon integration mutagenesis. Eight mutants were able to resist up to 15 mM selenite while the MIC for the wild-type strain was estimated as 4-6 mM selenite. The identification of the disrupted genes was carried out by Southern blot analysis and inverse PCR. The three resistant mutants containing only one insertion were further characterized. Tn5 disrupted a gene that encoded a protein which was closely related to proteins of the DedA family. This family represents a group of integral membrane proteins with completely unknown functions. Phenotypic characterization of the dedA mutants and selenite consumption experiments strongly suggest that DedA is involved in the uptake of selenite.
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Affiliation(s)
- Fouzia Ledgham
- Laboratoire de Chimie et Biochimie des Centres Redox Biologiques, DRDC/CB, CEA-Grenoble, France
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50
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Roos G, De Proft F, Geerlings P. Gas-Phase Stability of Tetrahedral Multiply Charged Anions: A Conceptual and Computational DFT Study. J Phys Chem A 2005; 109:652-8. [PMID: 16833392 DOI: 10.1021/jp046207m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Multiply charged anions (MCA's) are unstable relative to electron autoejection; however, the repulsive Coulomb barrier (RCB) provides electronic stability. In view of their interest in biological systems, the behavior of isolated AsO(4)(3-), PO(4)(3-), SO(4)(2-), and SeO(4)(2-) in the gas phase and in solution has been studied. To calculate the RCB values, the electrostatic and point charge model-two methods currently used in the literature-are applied, together with a recently introduced Conceptual Density Functional Theory (DFT) based approach. The relative stability of the above-mentioned MCA's is compared. The trends of the RCB are analyzed by including analogous compounds from the second and third row and by passing from dianionic to trianionic systems. Considering the effect of solvent, using the SCI-PCM solvent model, the evolution of the RCB when passing to higher dielectric constants is evaluated. The RCB is related to the properties of the system as polarizability/softness. Both a numerical and a conceptual correlation between the RCB and the global softness is found.
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Affiliation(s)
- Goedele Roos
- Vrije Universiteit Brussel, Algemene Chemie, Pleinlaan 2, B-1050 Brussels, Belgium
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