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André Pellerin - One of the best experts on this subject based on the ideXlab platform.
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the effect of temperature on sulfur and oxygen isotope fractionation by sulfate reducing bacteria desulfococcus multivorans
Fems Microbiology Letters, 2020Co-Authors: Gilad Antler, André Pellerin, Angeliki Marietou, Alexandra V Turchyn, Bo Barker JørgensenAbstract:Temperature influences microbiological growth and catabolic rates. Between 15 and 35 °C the growth rate and cell specific sulfate reduction rate of the sulfate reducing bacterium Desulfococcus multivorans increased with temperature. Sulfur isotope fractionation during sulfate reduction decreased with increasing temperature from 27.2 ‰ at 15 °C to 18.8 ‰ at 35 °C which is consistent with a decreasing reversibility of the metabolic pathway as the catabolic rate increases. Oxygen isotope fractionation, in contrast, decreased between 15 and 25 °C and then increased again between 25 and 35 °C, suggesting increasing reversibility in the first steps of the sulfate reducing pathway at higher temperatures. This points to a decoupling in the reversibility of sulfate reduction between the steps from the uptake of sulfate into the cell to the formation of Sulfite, relative to the whole pathway from sulfate to sulfide. This observation is consistent with observations of increasing sulfur isotope fractionation when sulfate reducing bacteria are living near their upper temperature limit. The oxygen isotope decoupling may be a first signal of changing physiology as the bacteria cope with higher temperatures.
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The Biogeochemical Sulfur Cycle of Marine Sediments.
Frontiers in microbiology, 2019Co-Authors: Bo Barker Jørgensen, Alyssa J. Findlay, André PellerinAbstract:Microbial dissimilatory sulfate reduction to sulfide is a predominant terminal pathway of organic matter mineralization in the anoxic seabed. Chemical or microbial oxidation of the produced sulfide establishes a complex network of pathways in the sulfur cycle, leading to intermediate sulfur species and partly back to sulfate. The intermediates include elemental sulfur, polysulfides, thiosulfate, and Sulfite, which are all substrates for further microbial oxidation, reduction or disproportionation. New microbiological discoveries, such as long-distance electron transfer through sulfide oxidizing cable bacteria, add to the complexity. Isotope exchange reactions play an important role for the stable isotope geochemistry and for the experimental study of sulfur transformations using radiotracers. Microbially catalyzed processes are partly reversible whereby the back-reaction affects our interpretation of radiotracer experiments and provides a mechanism for isotope fractionation. We here review the progress and current status in our understanding of the sulfur cycle in the seabed with respect to its microbial ecology, biogeochemistry, and isotope geochemistry.
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Deconstructing the Dissimilatory Sulfate Reduction Pathway: Isotope Fractionation of a Mutant Unable of Growth on Sulfate
Frontiers Media S.A., 2018Co-Authors: Emma Bertran, William D Leavitt, André Pellerin, Grant M. Zane, Judy D. Wall, Itay Halevy, Boswell A. Wing, David T. JohnstonAbstract:The sulfur isotope record provides key insight into the history of Earth's redox conditions. A detailed understanding of the metabolisms driving this cycle, and specifically microbial sulfate reduction (MSR), is crucial for accurate paleoenvironmental reconstructions. This includes a precise knowledge of the step-specific sulfur isotope effects during MSR. In this study, we aim at resolving the cellular-level fractionation factor during dissimilatory Sulfite reduction to sulfide within MSR, and use this measured isotope effect as a calibration to enhance our understanding of the biochemistry of Sulfite reduction. For this, we merge measured isotope effects associated with dissimilatory Sulfite reduction with a quantitative model that explicitly links net fractionation, reaction reversibility, and intracellular metabolite levels. The highly targeted experimental aspect of this study was possible by virtue of the availability of a deletion mutant strain of the model sulfate reducer Desulfovibrio vulgaris (strain Hildenborough), in which the Sulfite reduction step is isolated from the rest of the metabolic pathway owing to the absence of its QmoABC complex (ΔQmo). This deletion disrupts electron flux and prevents the reduction of adenosine phosphosulfate (APS) to Sulfite. When grown in open-system steady-state conditions at 10% maximum growth rate in the presence of Sulfite and lactate as electron donor, sulfur isotope fractionation factors averaged −15.9‰ (1 σ = 0.4), which appeared to be statistically indistinguishable from a pure enzyme study with dissimilatory Sulfite reductase. We coupled these measurements with an understanding of step-specific equilibrium and kinetic isotope effects, and furthered our mechanistic understanding of the biochemistry of Sulfite uptake and ensuing reduction. Our metabolically informed isotope model identifies flavodoxin as the most likely electron carrier performing the transfer of electrons to dissimilatory Sulfite reductase. This is in line with previous work on metabolic strategies adopted by sulfate reducers under different energy regimes, and has implications for our understanding of the plasticity of this metabolic pathway at the center of our interpretation of modern and palaeo-environmental records
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Table_1_Deconstructing the Dissimilatory Sulfate Reduction Pathway: Isotope Fractionation of a Mutant Unable of Growth on Sulfate.xlsx
2018Co-Authors: Emma Bertran, William D Leavitt, André Pellerin, Grant M. Zane, Judy D. Wall, Itay Halevy, Boswell A. Wing, David T. JohnstonAbstract:The sulfur isotope record provides key insight into the history of Earth's redox conditions. A detailed understanding of the metabolisms driving this cycle, and specifically microbial sulfate reduction (MSR), is crucial for accurate paleoenvironmental reconstructions. This includes a precise knowledge of the step-specific sulfur isotope effects during MSR. In this study, we aim at resolving the cellular-level fractionation factor during dissimilatory Sulfite reduction to sulfide within MSR, and use this measured isotope effect as a calibration to enhance our understanding of the biochemistry of Sulfite reduction. For this, we merge measured isotope effects associated with dissimilatory Sulfite reduction with a quantitative model that explicitly links net fractionation, reaction reversibility, and intracellular metabolite levels. The highly targeted experimental aspect of this study was possible by virtue of the availability of a deletion mutant strain of the model sulfate reducer Desulfovibrio vulgaris (strain Hildenborough), in which the Sulfite reduction step is isolated from the rest of the metabolic pathway owing to the absence of its QmoABC complex (ΔQmo). This deletion disrupts electron flux and prevents the reduction of adenosine phosphosulfate (APS) to Sulfite. When grown in open-system steady-state conditions at 10% maximum growth rate in the presence of Sulfite and lactate as electron donor, sulfur isotope fractionation factors averaged −15.9‰ (1 σ = 0.4), which appeared to be statistically indistinguishable from a pure enzyme study with dissimilatory Sulfite reductase. We coupled these measurements with an understanding of step-specific equilibrium and kinetic isotope effects, and furthered our mechanistic understanding of the biochemistry of Sulfite uptake and ensuing reduction. Our metabolically informed isotope model identifies flavodoxin as the most likely electron carrier performing the transfer of electrons to dissimilatory Sulfite reductase. This is in line with previous work on metabolic strategies adopted by sulfate reducers under different energy regimes, and has implications for our understanding of the plasticity of this metabolic pathway at the center of our interpretation of modern and palaeo-environmental records.
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Data_Sheet_1_Deconstructing the Dissimilatory Sulfate Reduction Pathway: Isotope Fractionation of a Mutant Unable of Growth on Sulfate.pdf
2018Co-Authors: Emma Bertran, William D Leavitt, André Pellerin, Grant M. Zane, Judy D. Wall, Itay Halevy, Boswell A. Wing, David T. JohnstonAbstract:The sulfur isotope record provides key insight into the history of Earth's redox conditions. A detailed understanding of the metabolisms driving this cycle, and specifically microbial sulfate reduction (MSR), is crucial for accurate paleoenvironmental reconstructions. This includes a precise knowledge of the step-specific sulfur isotope effects during MSR. In this study, we aim at resolving the cellular-level fractionation factor during dissimilatory Sulfite reduction to sulfide within MSR, and use this measured isotope effect as a calibration to enhance our understanding of the biochemistry of Sulfite reduction. For this, we merge measured isotope effects associated with dissimilatory Sulfite reduction with a quantitative model that explicitly links net fractionation, reaction reversibility, and intracellular metabolite levels. The highly targeted experimental aspect of this study was possible by virtue of the availability of a deletion mutant strain of the model sulfate reducer Desulfovibrio vulgaris (strain Hildenborough), in which the Sulfite reduction step is isolated from the rest of the metabolic pathway owing to the absence of its QmoABC complex (ΔQmo). This deletion disrupts electron flux and prevents the reduction of adenosine phosphosulfate (APS) to Sulfite. When grown in open-system steady-state conditions at 10% maximum growth rate in the presence of Sulfite and lactate as electron donor, sulfur isotope fractionation factors averaged −15.9‰ (1 σ = 0.4), which appeared to be statistically indistinguishable from a pure enzyme study with dissimilatory Sulfite reductase. We coupled these measurements with an understanding of step-specific equilibrium and kinetic isotope effects, and furthered our mechanistic understanding of the biochemistry of Sulfite uptake and ensuing reduction. Our metabolically informed isotope model identifies flavodoxin as the most likely electron carrier performing the transfer of electrons to dissimilatory Sulfite reductase. This is in line with previous work on metabolic strategies adopted by sulfate reducers under different energy regimes, and has implications for our understanding of the plasticity of this metabolic pathway at the center of our interpretation of modern and palaeo-environmental records.
Alexey Kamyshny - One of the best experts on this subject based on the ideXlab platform.
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Diurnal variations in sulfur transformations at the chemocline of a stratified freshwater lake
Biogeochemistry, 2019Co-Authors: Khoren Avetisyan, Alyssa J. Findlay, Werner Eckert, Alexey KamyshnyAbstract:In order to characterize biogeochemical sulfur cycling in the metalimnion of a thermally stratified freshwater lake, we followed changes in the concentrations and isotopic composition of sulfur species during a 24-h period, during which the chemocline oscillated at an amplitude of 5.3 m due to internal wave activity. Hourly sampling at a fixed depth (17.1 m) enabled study of redox changes during the transition from oxic to sulfidic conditions and vice versa. The oxidation–reduction potential, pH, conductivity and turbidity correlated linearly with the water temperature (a proxy for depth relative to the chemocline). The highest concentrations of thiosulfate and Sulfite were detected approximately 2.5 m below the chemocline. Concentrations of zero-valent sulfur increased ~ 10 fold when the chemocline rose into the photic zone due to phototrophic sulfide oxidation. Triple isotopic composition of sulfur species indicates a shift with depth from values typical for sulfate reduction right below the chemocline to values which may be explained by either sulfate reduction alone or by a combination of microbial sulfate reduction and microbial sulfate disproportionation. We conclude that consumption of hydrogen sulfide at the chemocline of Lake Kinneret is controlled by the combination of its chemical and/or chemotrophic oxidation to sulfur oxoanions and predominantly phototrophic oxidation to zero-valent sulfur.
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multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in yellowstone national park geothermal springs
Geochemical Transactions, 2014Co-Authors: Alexey Kamyshny, Zahra F Mansaray, Gregory K Druschel, James FarquhaAbstract:The paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, Sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling. Water samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (<6 μmol L-1) in the pools with low pH due to fast disproportionation of thiosulfate. In the pools with higher pH, the concentration of thiosulfate varies, depending on different geochemical pathways of thiosulfate formation. The δ34S values of sulfate in four systems were close to those calculated using a mixing line of the model based on dilution and boiling of a deep hot parent water body. In two pools δ34S values of sulfate varied significantly from the values calculated from this model. Sulfur isotope fractionation between ZVS and hydrogen sulfide was close to zero at pH < 4. At higher pH zero-valent sulfur is slightly heavier than hydrogen sulfide due to equilibration in the rhombic sulfur–polysulfide – hydrogen sulfide system. Triple sulfur isotope (32S, 33S, 34S) fractionation patterns in waters of hydrothermal pools are more consistent with redox processes involving intermediate sulfur species than with bacterial sulfate reduction. Small but resolved differences in ∆33S among species and between pools are observed. The variation of sulfate isotopic composition, the origin of differences in isotopic composition of sulfide and zero–valent sulfur, as well as differences in ∆33S of sulfide and sulfate are likely due to a complex network of abiotic redox reactions, including disproportionation pathways.
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Multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in Yellowstone National Park geothermal springs
Geochemical Transactions, 2014Co-Authors: Alexey Kamyshny, Zahra F Mansaray, Gregory K Druschel, James FarquharAbstract:Background The paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, Sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling. Results Water samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (
Guanghao Chen - One of the best experts on this subject based on the ideXlab platform.
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investigation on thiosulfate involved organics and nitrogen removal by a sulfur cycle based biological wastewater treatment process
Water Research, 2015Co-Authors: Jin Qian, Li Wei, Guanghao Chen, Yanxiang Cui, Rulong LiuAbstract:Abstract Thiosulfate, as an intermediate of biological sulfate/Sulfite reduction, can significantly improve nitrogen removal potential in a biological sulfur cycle-based process, namely the S ulfate reduction- A utotrophic denitrification- N itrification I ntegrated (SANI®) process. However, the related thiosulfate bio-activities coupled with organics and nitrogen removal in wastewater treatment lacked detailed examinations and reports. In this study, S2O32− transformation during biological SO42−/SO32− co-reduction coupled with organics removal as well as S2O32− oxidation coupled with chemolithotrophic denitrification were extensively evaluated under different experimental conditions. Thiosulfate is produced from the co-reduction of sulfate and Sulfite through biological pathway at an optimum pH of 7.5 for organics removal. And the produced S2O32− may disproportionate to sulfide and sulfate during both biological S2O32− reduction and oxidation most possibly carried out by Desulfovibrio-like species. Dosing the same amount of nitrate, pH was found to be the more direct factor influencing the denitritation activity than free nitrous acid (FNA) and the optimal pH for denitratation (7.0) and denitritation (8.0) activities were different. Spiking organics significantly improved both denitratation and denitritation activities while minimizing sulfide inhibition of NO3− reduction during thiosulfate-based denitrification. These findings in this study can improve the understanding of mechanisms of thiosulfate on organics and nitrogen removal in biological sulfur cycle-based wastewater treatment.
Jin Qian - One of the best experts on this subject based on the ideXlab platform.
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free sulfurous acid fsa inhibition of biological thiosulfate reduction btr in the sulfur cycle driven wastewater treatment process
Chemosphere, 2017Co-Authors: Lianlian Wang, Yaoguo Wu, Xing Chang, Baixue Deng, Philip L. Bond, Yuhan Zhang, Jin Qian, Qin Li, Qilin WangAbstract:Abstract A sulfur cycle-based bioprocess for co-treatment of wet flue gas desulfurization (WFGD) wastes with freshwater sewage has been developed. In this process the removal of organic carbon is mainly associated with biological sulfate or Sulfite reduction. Thiosulfate is a major intermediate during biological sulfate/Sulfite reduction, and its reduction to sulfide is the rate-limiting step. In this study, the impacts of saline Sulfite (the ionized form: HSO 3 − + SO 3 2− ) and free sulfurous acid (FSA, the unionized form: H 2 SO 3 ) sourced from WGFD wastes on the biological thiosulfate reduction (BTR) activities were thoroughly investigated. The BTR activity and sulfate/Sulfite-reducing bacteria (SRB) populations in the thiosulfate-reducing up-flow anaerobic sludge bed (UASB) reactor decreased when the FSA was added to the UASB influent. Batch experiment results confirmed that FSA, instead of saline Sulfite, was the true inhibitor of BTR. And BTR activities dropped by 50% as the FSA concentrations were increased from 8.0 × 10 −8 to 2.0 × 10 −4 mg H 2 SO 3 -S/L. From an engineering perspective, the findings of this study provide some hints on how to ensure effective thiosulfate accumulation in biological sulfate/Sulfite reduction for the subsequent denitrification/denitritation. Such manipulation would result in higher nitrogen removal rates in this co-treatment process of WFGD wastes with municipal sewage.
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investigation on thiosulfate involved organics and nitrogen removal by a sulfur cycle based biological wastewater treatment process
Water Research, 2015Co-Authors: Jin Qian, Li Wei, Guanghao Chen, Yanxiang Cui, Rulong LiuAbstract:Abstract Thiosulfate, as an intermediate of biological sulfate/Sulfite reduction, can significantly improve nitrogen removal potential in a biological sulfur cycle-based process, namely the S ulfate reduction- A utotrophic denitrification- N itrification I ntegrated (SANI®) process. However, the related thiosulfate bio-activities coupled with organics and nitrogen removal in wastewater treatment lacked detailed examinations and reports. In this study, S2O32− transformation during biological SO42−/SO32− co-reduction coupled with organics removal as well as S2O32− oxidation coupled with chemolithotrophic denitrification were extensively evaluated under different experimental conditions. Thiosulfate is produced from the co-reduction of sulfate and Sulfite through biological pathway at an optimum pH of 7.5 for organics removal. And the produced S2O32− may disproportionate to sulfide and sulfate during both biological S2O32− reduction and oxidation most possibly carried out by Desulfovibrio-like species. Dosing the same amount of nitrate, pH was found to be the more direct factor influencing the denitritation activity than free nitrous acid (FNA) and the optimal pH for denitratation (7.0) and denitritation (8.0) activities were different. Spiking organics significantly improved both denitratation and denitritation activities while minimizing sulfide inhibition of NO3− reduction during thiosulfate-based denitrification. These findings in this study can improve the understanding of mechanisms of thiosulfate on organics and nitrogen removal in biological sulfur cycle-based wastewater treatment.
Christiane Dahl - One of the best experts on this subject based on the ideXlab platform.
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Importance of the DsrMKJOP complex for sulfur oxidation in Allochromatium vinosum and phylogenetic analysis of related complexes in other prokaryotes
Archives of Microbiology, 2006Co-Authors: Johannes Sander, Sabine Engels-schwarzlose, Christiane DahlAbstract:In the phototrophic sulfur bacterium Allochromatium vinosum , sulfur of oxidation state zero stored in intracellular sulfur globules is an obligate intermediate during the oxidation of sulfide and thiosulfate. The proteins encoded in the d issimilatory s ulfite r eductase ( dsr ) locus are essential for the oxidation of the stored sulfur. DsrMKJOP form a membrane-spanning complex proposed to accept electrons from or to deliver electrons to cytoplasmic sulfur-oxidizing proteins. In frame deletion mutagenesis showed that each individual of the complex-encoding genes is an absolute requirement for the oxidation of the stored sulfur in Alc. vinosum . Complementation of the ΔdsrJ mutant using the conjugative broad host range plasmid pBBR1-MCS2 and the dsr promoter was successful. The importance of the DsrMKJOP complex is underlined by the fact that the respective genes occur in all currently sequenced genomes of sulfur-forming bacteria such as Thiobacillus denitrificans and Chlorobaculum tepidum . Furthermore, closely related genes are present in the genomes of sulfate- and Sulfite-reducing prokaryotes. A phylogenetic analysis showed that most dsr genes from sulfide oxidizers are clearly separated of those from sulfate reducers. Surprisingly, the dsrMKJOP genes of the Chlorobiaceae all cluster together with those of the sulfate/Sulfite-reducing prokaryotes, indicating a lateral gene transfer at the base of the Chlorobiaceae.
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novel genes of the dsr gene cluster and evidence for close interaction of dsr proteins during sulfur oxidation in the phototrophic sulfur bacterium allochromatium vinosum
Journal of Bacteriology, 2005Co-Authors: Christiane Dahl, Johannes Sander, Sabine Engels, Andrea S Pottsperling, Andrea Schulte, Yvonne Lubbe, Oliver Deuster, Daniel C BruneAbstract:Seven new genes designated dsrLJOPNSR were identified immediately downstream of dsrABEFHCMK, completing the dsr gene cluster of the phototrophic sulfur bacterium Allochromatium vinosum D (DSM 180(T)). Interposon mutagenesis proved an essential role of the encoded proteins for the oxidation of intracellular sulfur, an obligate intermediate during the oxidation of sulfide and thiosulfate. While dsrR and dsrS encode cytoplasmic proteins of unknown function, the other genes encode a predicted NADPH:acceptor oxidoreductase (DsrL), a triheme c-type cytochrome (DsrJ), a periplasmic iron-sulfur protein (DsrO), and an integral membrane protein (DsrP). DsrN resembles cobyrinic acid a,c-diamide synthases and is probably involved in the biosynthesis of siro(heme)amide, the prosthetic group of the dsrAB-encoded Sulfite reductase. The presence of most predicted Dsr proteins in A. vinosum was verified by Western blot analysis. With the exception of the constitutively present DsrC, the formation of Dsr gene products was greatly enhanced by sulfide. DsrEFH were purified from the soluble fraction and constitute a soluble alpha(2)beta(2)gamma(2)-structured 75-kDa holoprotein. DsrKJO were purified from membranes pointing at the presence of a transmembrane electron-transporting complex consisting of DsrKMJOP. In accordance with the suggestion that related complexes from dissimilatory sulfate reducers transfer electrons to Sulfite reductase, the A. vinosum Dsr complex is copurified with Sulfite reductase, DsrEFH, and DsrC. We therefore now have an ideal and unique possibility to study the interaction of Sulfite reductase with other proteins and to clarify the long-standing problem of electron transport from and to Sulfite reductase, not only in phototrophic bacteria but also in sulfate-reducing prokaryotes.
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31 siroheme Sulfite reductase type protein from pyrobaculum islandicum
Methods in Enzymology, 2001Co-Authors: Christiane Dahl, Michael Molitor, Hans G. TrüperAbstract:Publisher Summary Elemental sulfur is used as an electron acceptor for chemolithotrophic growth on H 2 of the hyperthermophilic crenarchaeote Pyrobaculum islandicum . This organism has an optimum growth temperature of 100° and was isolated from an Icelandic geothermal power plant. During organotrophic growth, P. islandicum is also able to grow using Sulfite, thiosulfate, cystine, and oxidized glutathione as electron acceptors but it is not able to reduce sulfate. In all organisms capable of reducing Sulfite during anaerobic respiration investigated thus far, the six-electron reduction of Sulfite to sulfde is catalyzed by the enzyme Sulfite reductase. The Sulfite reductase-type protein from P. islandicum , which is the subject of this article, shares several common characteristics with dissimilatory Sulfite reductases. All of these enzymes consist of two different polypeptides in an α 2 β 2 structure and contain siroheme, nonheme iron, and acid-labile sulfide. In addition, the primary sequence of the P. islandicum Sulfite reductase and those available from dissimilatory sulfate reducers and the phototrophic sulfur oxidizer A. vinosum show remarkable similarity.
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Dissimilatory ATP sulfurylase from Archaeoglobus fulgidus
Methods in enzymology, 2001Co-Authors: Detlef Sperling, Hans G. Trüper, Ulrike Kappler, Christiane DahlAbstract:Publisher Summary The hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus belongs to the kingdom of Euryarchaeota and is grouped with the Methanomicrobiales/extremehalophiles cluster. A. fulgidus has been shown to contain the complete pathway for dissimilatory sulfate reduction known from Bacteria. ATP sulfurylase (MgATP-sulfate adenylyltransferase) is the key enzyme in dissimilatory and assimilatory sulfate reduction. It catalyzes the activation of inorganic sulfate by ATP to give pyrophosphate and adenosine 5'-phosphosulfate (APS), the shared intermediate in these two pathways. In dissimilatory sulfate reduction, APS reductase catalyzes the reduction of APS to AMP and Sulfite, which is reduced to sulfide by Sulfite reductase. Dissimilatory ATP sulfurylase has also been found in some chemotrophic and phototrophic sulfur-oxidizing bacteria in which it functions in the opposite direction, releasing sulfate and ATP from APS. Dissimilatory ATP sulfurylase have been isolated and characterized from A. fulgidus . The gene encoding this archaeal ATP sulfurylase has been cloned and expressed in Escherichia coli . However, the properties of the recombinant enzyme show significant differences to those of the native enzyme.
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[33] Sulfite reductase and APS reductase from Archaeoglobus fulgidus
Methods in enzymology, 2001Co-Authors: Christiane Dahl, Hans G. TrüperAbstract:Publisher Summary Archaeoglobus fulgidus carries out sulfate reduction via the pathway originally proposed for bacterial species. All steps of sulfate reduction occur in the cytoplasm, implying that sulfate must be transported across the cytoplasmic membrane. Sulfate transport has not been studied in A. fulgidus , but may resemble that of marine bacterial sulfate reducers, which use sodium ions for the symport of sulfate. The enzyme dissimilatory Sulfite reductase catalyzes the six-electron reduction of Sulfite to sulfide, which is the central energy-conserving step of sulfate respiration. The natural electron donor of Sulfite reductase in sulfate reducers is not known. Thiosulfate reduction in A. fulgidus has not been studied biochemically. Analysis of the A. fulgidus genome sequence revealed the presence of genes encoding several putative molybdopterinbinding oxidoreductases with thiosulfate or polysulfide as potential substrates. This chapter focuses on the purification and characterization of APS reductase and Sulfite reductase from A. fulgidus .
