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Joanne M. Santini - One of the best experts on this subject based on the ideXlab platform.
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Microbial oxidation of arsenite in a subarctic environment: diversity of arsenite oxidase genes and identification of a psychrotolerant arsenite oxidiser.
BMC Microbiology, 2010Co-Authors: Thomas H. Osborne, Heather E. Jamieson, Karen A. Hudson-edwards, D. Kirk Nordstrom, Stephen R. Walker, Seamus A. Ward, Joanne M. SantiniAbstract:Background: Arsenic is toxic to most living cells. The two soluble inorganic forms of arsenic are arsenite (+3) and arsenate (+5), with arsenite the more toxic. Prokaryotic metabolism of arsenic has been reported in both thermal and moderate environments and has been shown to be involved in the redox cycling of arsenic. No arsenic metabolism (either dissimilatory arsenate reduction or arsenite oxidation) has ever been reported in cold environments (i.e. < 10°C). Results: Our study site is located 512 kilometres south of the Arctic Circle in the Northwest Territories, Canada in an inactive gold mine which contains mine waste water in excess of 50 mM arsenic. Several thousand tonnes of arsenic trioxide dust are stored in underground chambers and microbial biofilms grow on the chamber walls below seepage points rich in arsenite-containing solutions. We compared the arsenite oxidisers in two subsamples (which differed in arsenite concentration) collected from one biofilm. ‘Species’ (sequence) richness did not differ between subsamples, but the relative importance of the three identifiable clades did. An arsenite-oxidising bacterium (designated GM1) was isolated, and was shown to oxidise arsenite in the early exponential growth phase and to grow at a broad range of temperatures (4-25°C). Its arsenite oxidase was constitutively expressed and functioned over a broad temperature range. Conclusions: The diversity of arsenite oxidisers does not significantly differ from two subsamples of a microbial biofilm that vary in arsenite concentrations. GM1 is the first psychrotolerant arsenite oxidiser to be isolated with the ability to grow below 10°C. This ability to grow at low temperatures could be harnessed for arsenic bioremediation in moderate to cold climates.
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Protein Film Voltammetry of Arsenite Oxidase from the Chemolithoautotrophic Arsenite-Oxidizing Bacterium NT-26†
Biochemistry, 2006Co-Authors: Paul V. Bernhardt, Joanne M. SantiniAbstract:The chemolithoautotrophic bacterium NT-26 (isolated from a gold mine in the Northern Territory of Australia) is unusual in that it acquires energy by oxidizing arsenite to arsenate while most other arsenic-oxidizing organisms perform this reaction as part of a detoxification mechanism against the potentially harmful arsenite [present as As(OH)3 at neutral pH]. The enzyme that performs this reaction in NT-26 is the molybdoenzyme arsenite oxidase, and it has been previously isolated and characterized. Here we report the direct (unmediated) electrochemistry of NT-26 arsenite oxidase confined to the surface of a pyrolytic graphite working electrode. We have been able to demonstrate that the enzyme functions natively while adsorbed on the electrode where it displays stable and reproducible catalytic electrochemistry in the presence of arsenite. We report a pH dependence of the catalytic electrochemical potential of −33 mV/pH unit that is indicative of proton-coupled electron transfer. We also have performed ca...
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Arsenite oxidation by the heterotroph Hydrogenophaga sp. str. NT-14: the arsenite oxidase and its physiological electron acceptor.
Biochimica et biophysica acta, 2004Co-Authors: Rachel N Vanden Hoven, Joanne M. SantiniAbstract:Heterotrophic arsenite oxidation by Hydrogenophaga sp. str. NT-14 is coupled to the reduction of oxygen and appears to yield energy for growth. Purification and partial characterization of the arsenite oxidase revealed that it (1). contains two heterologous subunits, AroA (86 kDa) and AroB (16 kDa), (2). has a native molecular mass of 306 kDa suggesting an alpha(3)beta(3) configuration, and (3). contains molybdenum and iron as cofactors. Although the Hydrogenophaga sp. str. NT-14 arsenite oxidase shares similarities to the arsenite oxidases purified from NT-26 and Alcaligenes faecalis, it differs with respect to activity and overall conformation. A c-551-type cytochrome was purified from Hydrogenophaga sp. str. NT-14 and appears to be the physiological electron acceptor for the arsenite oxidase. The cytochrome can also accept electrons from the purified NT-26 arsenite oxidase. A hypothetical electron transport chain for heterotrophic arsenite oxidation is proposed.
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Arsenite oxidation by the heterotroph Hydrogenophaga sp. str. NT-14: the arsenite oxidase and its physiological electron acceptor
Biochimica et Biophysica Acta, 2004Co-Authors: Rachel N. Vanden Hoven, Joanne M. SantiniAbstract:Abstract Heterotrophic arsenite oxidation by Hydrogenophaga sp. str. NT-14 is coupled to the reduction of oxygen and appears to yield energy for growth. Purification and partial characterization of the arsenite oxidase revealed that it (1) contains two heterologous subunits, AroA (86 kDa) and AroB (16 kDa), (2) has a native molecular mass of 306 kDa suggesting an α3β3 configuration, and (3) contains molybdenum and iron as cofactors. Although the Hydrogenophaga sp. str. NT-14 arsenite oxidase shares similarities to the arsenite oxidases purified from NT-26 and Alcaligenes faecalis, it differs with respect to activity and overall conformation. A c-551-type cytochrome was purified from Hydrogenophaga sp. str. NT-14 and appears to be the physiological electron acceptor for the arsenite oxidase. The cytochrome can also accept electrons from the purified NT-26 arsenite oxidase. A hypothetical electron transport chain for heterotrophic arsenite oxidation is proposed.
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Molybdenum-Containing Arsenite Oxidase of the Chemolithoautotrophic Arsenite Oxidizer NT-26
Journal of Bacteriology, 2004Co-Authors: Joanne M. Santini, Rachel N. Vanden HovenAbstract:The chemolithoautotroph NT-26 oxidizes arsenite to arsenate by using a periplasmic arsenite oxidase. Purification and preliminary characterization of the enzyme revealed that it (i) contains two heterologous subunits, AroA (98 kDa) and AroB (14 kDa); (ii) has a native molecular mass of 219 kDa, suggesting an α2β2 configuration; and (iii) contains two molybdenum and 9 or 10 iron atoms per α2β2 unit. The genes that encode the enzyme have been cloned and sequenced. Sequence analyses revealed similarities to the arsenite oxidase of Alcaligenes faecalis, the putative arsenite oxidase of the beta-proteobacterium ULPAs1, and putative proteins of Aeropyrum pernix, Sulfolobus tokodaii, and Chloroflexus aurantiacus. Interestingly, the AroA subunit was found to be similar to the molybdenum-containing subunits of enzymes in the dimethyl sulfoxide reductase family, whereas the AroB subunit was found to be similar to the Rieske iron-sulfur proteins of cytochrome bc1 and b6f complexes. The NT-26 arsenite oxidase is probably exported to the periplasm via the Tat secretory pathway, with the AroB leader sequence used for export. Confirmation that NT-26 obtains energy from the oxidation of arsenite was obtained, as an aroA mutant was unable to grow chemolithoautotrophically with arsenite. This mutant could grow heterotrophically in the presence of arsenite; however, the arsenite was not oxidized to arsenate.
Enrica Canzi - One of the best experts on this subject based on the ideXlab platform.
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Arsenite Oxidation in Ancylobacter dichloromethanicus As3-1b Strain: Detection of Genes Involved in Arsenite Oxidation and CO2 Fixation
Current Microbiology, 2012Co-Authors: Vincenza Andreoni, Raffaella Zanchi, Cristina Romagnoli, Anna Corsini, Lucia Cavalca, Enrica CanziAbstract:The aim of this study was to characterize a facultative chemolithotrophic arsenite-oxidizing bacterium by evaluating the growth and the rate of arsenite oxidation and to investigate the genetic determinants for arsenic resistance and CO2 fixation. The strain under study, Ancylobacter dichloromethanicus As3-1b, in a minimal medium containing 3 mM of arsenite as electron donor and 6 mM of CO2–bicarbonate as the C source, has a doubling time (td) of 8.1 h. Growth and arsenite oxidation were significantly enhanced by the presence of 0.01 % yeast extract, decreasing the t d to 4.3 h. The strain carried arsenite oxidase (aioA) gene highly similar to those of previously reported arsenite-oxidizing Alpha-proteobacteria. The RuBisCO Type-I (cbbL) gene was amplified and sequenced too, underscoring the ability of As3-1b to carry out autotrophic As(III) oxidation. The results suggest that A. dichloromethanicus As3-1b can be a good candidate for the oxidation of arsenite in polluted waters or groundwaters.
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Arsenite oxidation in Ancylobacter dichloromethanicus As3-1b strain: Detection of genes involved in arsenite oxidation and CO 2 fixation
Current Microbiology, 2012Co-Authors: Vincenza Andreoni, Raffaella Zanchi, Cristina Romagnoli, Anna Corsini, Lucia Cavalca, Enrica CanziAbstract:The aim of this study was to characterize a facultative chemolithotrophic arsenite-oxidizing bacterium by evaluating the growth and the rate of arsenite oxidation and to investigate the genetic determinants for arsenic resistance and CO 2 fixation. The strain under study, Ancylobacter dichloromethanicus As3-1b, in a minimal medium containing 3 mM of arsenite as electron donor and 6 mM of CO 2 -bicarbonate as the C source, has a doubling time (t d ) of 8.1 h. Growth and arsenite oxidation were significantly enhanced by the presence of 0.01 % yeast extract, decreasing the t d to 4.3 h. The strain carried arsenite oxidase (aioA) gene highly similar to those of previously reported arsenite-oxidizing Alpha-proteobacteria. The RuBisCO Type-I (cbbL) gene was amplified and sequenced too, underscoring the ability of As3-1b to carry out autotrophic As(III) oxidation. The results suggest that A. dichloromethanicus As3-1b can be a good candidate for the oxidation of arsenite in polluted waters or groundwaters. © 2012 Springer Science+Business Media, LLC.
Rachel N. Vanden Hoven - One of the best experts on this subject based on the ideXlab platform.
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Arsenite oxidation by the heterotroph Hydrogenophaga sp. str. NT-14: the arsenite oxidase and its physiological electron acceptor
Biochimica et Biophysica Acta, 2004Co-Authors: Rachel N. Vanden Hoven, Joanne M. SantiniAbstract:Abstract Heterotrophic arsenite oxidation by Hydrogenophaga sp. str. NT-14 is coupled to the reduction of oxygen and appears to yield energy for growth. Purification and partial characterization of the arsenite oxidase revealed that it (1) contains two heterologous subunits, AroA (86 kDa) and AroB (16 kDa), (2) has a native molecular mass of 306 kDa suggesting an α3β3 configuration, and (3) contains molybdenum and iron as cofactors. Although the Hydrogenophaga sp. str. NT-14 arsenite oxidase shares similarities to the arsenite oxidases purified from NT-26 and Alcaligenes faecalis, it differs with respect to activity and overall conformation. A c-551-type cytochrome was purified from Hydrogenophaga sp. str. NT-14 and appears to be the physiological electron acceptor for the arsenite oxidase. The cytochrome can also accept electrons from the purified NT-26 arsenite oxidase. A hypothetical electron transport chain for heterotrophic arsenite oxidation is proposed.
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Molybdenum-Containing Arsenite Oxidase of the Chemolithoautotrophic Arsenite Oxidizer NT-26
Journal of Bacteriology, 2004Co-Authors: Joanne M. Santini, Rachel N. Vanden HovenAbstract:The chemolithoautotroph NT-26 oxidizes arsenite to arsenate by using a periplasmic arsenite oxidase. Purification and preliminary characterization of the enzyme revealed that it (i) contains two heterologous subunits, AroA (98 kDa) and AroB (14 kDa); (ii) has a native molecular mass of 219 kDa, suggesting an α2β2 configuration; and (iii) contains two molybdenum and 9 or 10 iron atoms per α2β2 unit. The genes that encode the enzyme have been cloned and sequenced. Sequence analyses revealed similarities to the arsenite oxidase of Alcaligenes faecalis, the putative arsenite oxidase of the beta-proteobacterium ULPAs1, and putative proteins of Aeropyrum pernix, Sulfolobus tokodaii, and Chloroflexus aurantiacus. Interestingly, the AroA subunit was found to be similar to the molybdenum-containing subunits of enzymes in the dimethyl sulfoxide reductase family, whereas the AroB subunit was found to be similar to the Rieske iron-sulfur proteins of cytochrome bc1 and b6f complexes. The NT-26 arsenite oxidase is probably exported to the periplasm via the Tat secretory pathway, with the AroB leader sequence used for export. Confirmation that NT-26 obtains energy from the oxidation of arsenite was obtained, as an aroA mutant was unable to grow chemolithoautotrophically with arsenite. This mutant could grow heterotrophically in the presence of arsenite; however, the arsenite was not oxidized to arsenate.
Vincenza Andreoni - One of the best experts on this subject based on the ideXlab platform.
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Arsenite Oxidation in Ancylobacter dichloromethanicus As3-1b Strain: Detection of Genes Involved in Arsenite Oxidation and CO2 Fixation
Current Microbiology, 2012Co-Authors: Vincenza Andreoni, Raffaella Zanchi, Cristina Romagnoli, Anna Corsini, Lucia Cavalca, Enrica CanziAbstract:The aim of this study was to characterize a facultative chemolithotrophic arsenite-oxidizing bacterium by evaluating the growth and the rate of arsenite oxidation and to investigate the genetic determinants for arsenic resistance and CO2 fixation. The strain under study, Ancylobacter dichloromethanicus As3-1b, in a minimal medium containing 3 mM of arsenite as electron donor and 6 mM of CO2–bicarbonate as the C source, has a doubling time (td) of 8.1 h. Growth and arsenite oxidation were significantly enhanced by the presence of 0.01 % yeast extract, decreasing the t d to 4.3 h. The strain carried arsenite oxidase (aioA) gene highly similar to those of previously reported arsenite-oxidizing Alpha-proteobacteria. The RuBisCO Type-I (cbbL) gene was amplified and sequenced too, underscoring the ability of As3-1b to carry out autotrophic As(III) oxidation. The results suggest that A. dichloromethanicus As3-1b can be a good candidate for the oxidation of arsenite in polluted waters or groundwaters.
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Arsenite oxidation in Ancylobacter dichloromethanicus As3-1b strain: Detection of genes involved in arsenite oxidation and CO 2 fixation
Current Microbiology, 2012Co-Authors: Vincenza Andreoni, Raffaella Zanchi, Cristina Romagnoli, Anna Corsini, Lucia Cavalca, Enrica CanziAbstract:The aim of this study was to characterize a facultative chemolithotrophic arsenite-oxidizing bacterium by evaluating the growth and the rate of arsenite oxidation and to investigate the genetic determinants for arsenic resistance and CO 2 fixation. The strain under study, Ancylobacter dichloromethanicus As3-1b, in a minimal medium containing 3 mM of arsenite as electron donor and 6 mM of CO 2 -bicarbonate as the C source, has a doubling time (t d ) of 8.1 h. Growth and arsenite oxidation were significantly enhanced by the presence of 0.01 % yeast extract, decreasing the t d to 4.3 h. The strain carried arsenite oxidase (aioA) gene highly similar to those of previously reported arsenite-oxidizing Alpha-proteobacteria. The RuBisCO Type-I (cbbL) gene was amplified and sequenced too, underscoring the ability of As3-1b to carry out autotrophic As(III) oxidation. The results suggest that A. dichloromethanicus As3-1b can be a good candidate for the oxidation of arsenite in polluted waters or groundwaters. © 2012 Springer Science+Business Media, LLC.
Zigang Dong - One of the best experts on this subject based on the ideXlab platform.
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Tpl2 Is a Key Mediator of Arsenite-Induced Signal Transduction
Cancer Research, 2009Co-Authors: Ann M. Bode, Zigang DongAbstract:Arsenite is a well-known human carcinogen that especially targets skin. The tumor progression locus 2 (Tpl2) gene encodes a serine/threonine protein kinase that is overexpressed in various cancer cells. However, the relevance of Tpl2 in arsenite-induced carcinogenesis and the underlying mechanisms remain to be explored. We show that arsenite increased Tpl2 kinase activity and its phosphorylation in mouse epidermal JB6 P+ cells in a dose- and time-dependent manner. Exposure to arsenite resulted in a marked induction of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2), important mediators of inflammation and tumor promotion. Treatment with a Tpl2 kinase inhibitor or Tpl2 short hairpin RNA suppressed COX-2 expression and PGE2 production induced by arsenite treatment, suggesting that Tpl2 is critical in arsenite-induced carcinogenesis. We also found that arsenite-induced phosphorylation of extracellular signal-regulated kinases (ERK) or c-Jun NH2-terminal kinases (JNK) was markedly suppressed by Tpl2 kinase inhibitor or Tpl2 short hairpin RNA. Inhibition of arsenite-induced ERK or JNK signaling using a pharmacologic inhibitor of ERK or JNK substantially blocked COX-2 expression. Furthermore, inhibition of Tpl2 reduced the arsenite-induced promoter activity of NF-κB and activator protein-1 (AP-1), indicating that NF-κB and AP-1 are downstream transducers of arsenite-triggered Tpl2. Our results show that Tpl2 plays a key role in arsenite-induced COX-2 expression and PGE2 production and further elucidate the role of Tpl2 in arsenite signals that activate ERK/JNK and NF-κB/AP-1 in JB6 P+ cells. [Cancer Res 2009;69(20):8043–9]
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Inhibition of arsenite-induced apoptosis by aspirin
Anticancer Research, 2001Co-Authors: Nanyue Chen, Wei-ya Ma, Zigang DongAbstract:Arsenite exposure and subsequent arsenite-induced toxicity and carcinogenesis are common in many countries. Thus the study of chemopreventive compounds that inhibit arsenite-induced toxicity and carcinogenesis is very valuable. In the present work, we investigated the effect of aspirin on arsenite-induced apoptosis and signal transduction by means of luciferase activity, apoptosis analysis and Western blotting. Arsenite induced AP-1 transcriptional activity at the same concentration (20 μM) as was effective for inducing apoptosis. Arsenite-induced apoptosis and AP-1 transactivation in JB6 cells were blocked by aspirin and salicylate (SA). Both aspirin and SA inhibited arsenite-induced phosphorylation of Erks, but had no effect on phosphorylation of JNKs. SA inhibited arsenite-induced phosphorylation of p38 kinase, but aspirin did not. These results indicate that aspirin and SA inhibit arsenite-induced apoptosis through the inhibition of the Erks/AP-1 pathway.
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Activation of PKC is required for arsenite-induced signal transduction
Journal of Environmental Pathology Toxicology and Oncology, 2000Co-Authors: Nanyue Chen, Wei-ya Ma, Chuanshu Huang, Min Ding, Zigang DongAbstract:Trivalent arsenic (arsenite) is a human carcinogen. However, the molecular mechanism of arsenite-induced carcinogenesis is still not well understood. In this study, we found that arsenite induced translocation of PKCe, PKC8, and PKCa from cytosol to membranes. Rottlerin, a selective inhibitor for PKCδ, and safingol, a specific inhibitor for PKCa, both markedly inhibited arsenite-induced AP-1 activity. These inhibitory effects by rottlerin and safingol appeared to be dose dependent. Arsenite-induced phosphorylation of Erks was inhibited by rottlerin, while safingol inhibited arsenite-induced phosphorylation of JNKs and p38 kinases. Dominant negative mutant transfectant of PKCe markedly blocked arsenite-induced AP-1 activity and the phosphorylation of Erks, JNKs, and p38 kinases. These data demonstrate that PKCδ, PKC£, and PKCa mediate arsenite-induced AP-1 activation in JB6 cells through different MAP kinase (Erks, JNKs, and p38 kinases) pathways.
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Requirement of Erk, but Not JNK, for Arsenite-induced Cell Transformation
Journal of Biological Chemistry, 1999Co-Authors: Chuanshu Huang, Wei-ya Ma, Jingxia Li, Angela Goranson, Zigang DongAbstract:Abstract Trivalent arsenic (arsenite, As3+) is a human carcinogen, which is associated with cancers of skin, lung, liver, and bladder. However, the mechanism by which arsenite causes cancer is not well understood. In this study, we found that exposure of Cl 41 cells, a well characterized mouse epidermal cell model for tumor promotion, to a low concentration of arsenite (