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Benjamin Erable - One of the best experts on this subject based on the ideXlab platform.
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Nitrate and Nitrite Reduction activity of activated sludge microcosm in a highly alkaline environment with solid cementitious material
International Biodeterioration and Biodegradation, 2020Co-Authors: Nadège Durban, Vanessa Sonois-mazars, Pierre Albina, Alexandra Bertron, Achim Albrecht, Jean-charles Robinet, Benjamin ErableAbstract:Denitrification is a major biological process contributing to nitrate and Nitrite Reduction. However, this process remains poorly understood at alkaline pH although such conditions can be encountered in natural (e.g. soda lakes) or industrial environments (e.g. geological waste repositories with cementitious materials). To investigate the nitrate Reduction (NR) rate for pH > 9.5 in a cementitious environment, several batch reactors were implemented, with cement leachate or with hardened cement paste (HCP). In the experiments carried out with cement leachate, NR dropped from 0.72 mM/h at pH 9.5 to 0.17 mM/h at pH > 11, while the concentration of Nitrite increased. The NR was inhibited at pH close to 12, as was the Nitrite Reduction at pH above 11. In the reactor containing HCP, the NR rate was 0.75 mM/h at pH close to 10. Calcite precipitated on the HCP surface. Epifluorescence microscopy observations coupled with DNA labelling suggested the presence of microorganisms attached to the HCP surface. This was confirmed by biological growth coupled with NR activity after the transfer of the HCP into a new medium, considered to be sterile. The bacterial community analysis showed that the highly selective culture conditions led to the selection of two species: Halomonas sp. and a species known for its versatile metabolism and ability to form biofilms, i.e. Thauera sp.
Jay L Zweier - One of the best experts on this subject based on the ideXlab platform.
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characterization of the mechanism and magnitude of cytoglobin mediated Nitrite Reduction and nitric oxide generation under anaerobic conditions
Journal of Biological Chemistry, 2012Co-Authors: Craig Hemann, Tamer M. Abdelghany, Mohamed A Elmahdy, Jay L ZweierAbstract:Cytoglobin (Cygb) is a recently discovered cytoplasmic heme-binding globin. Although multiple hemeproteins have been reported to function as Nitrite reductases in mammalian cells, it is unknown whether Cygb can also reduce Nitrite to nitric oxide (NO). The mechanism, magnitude, and quantitative importance of Cygb-mediated Nitrite Reduction in tissues have not been reported. To investigate this pathway and its quantitative importance, EPR spectroscopy, spectrophotometric measurements, and chemiluminescence NO analyzer studies were performed. Under anaerobic conditions, mixing Nitrite with ferrous-Cygb triggered NO formation that was trapped and detected using EPR spin trapping. Spectrophotometric studies revealed that Nitrite binding to ferrous-Cygb is followed by formation of ferric-Cygb and NO. The kinetics and magnitude of Cygb-mediated NO formation were characterized. It was observed that Cygb-mediated NO generation increased linearly with the increase of Nitrite concentration under anaerobic conditions. This Cygb-mediated NO production greatly increased with acidosis and near-anoxia as occur in ischemic conditions. With the addition of Nitrite, soluble guanylyl cyclase activation was significantly higher in normal smooth muscle cells compared with Cygb knocked down cells with Cygb accounting for ∼40% of the activation in control cells and ∼60% in cells subjected to hypoxia for 48 h. Overall, these studies show that Cygb-mediated Nitrite Reduction can play an important role in NO generation and soluble guanylyl cyclase activation under hypoxic conditions, with this process regulated by pH, oxygen tension, Nitrite concentration, and the redox state of the cells.
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Characterization of the Mechanism and Magnitude of Cytoglobin-mediated Nitrite Reduction and Nitric Oxide Generation under Anaerobic Conditions
The Journal of biological chemistry, 2012Co-Authors: Craig Hemann, Tamer M. Abdelghany, Mohamed A. El-mahdy, Jay L ZweierAbstract:Abstract Cytoglobin (Cygb) is a recently discovered cytoplasmic heme-binding globin. Although multiple heme proteins have been reported to function as Nitrite reductases in mammalian cells, it is unknown whether Cygb can also reduce Nitrite to nitric oxide (NO). The mechanism, magnitude, and quantitative importance of Cygb-mediated Nitrite Reduction in tissues have not been reported. To investigate this pathway and its quantitative importance, electron paramagnetic resonance (EPR) spectroscopy, spectrophotometric measurements, and chemiluminescence NO analyzer studies were performed. Under anaerobic conditions, mixing Nitrite with ferrous-Cygb triggered NO formation that was trapped and detected using EPR spin trapping. Spectrophotometric studies revealed that Nitrite binding to ferrous-Cygb is followed by formation of ferric-Cygb and NO. The kinetics and magnitude of Cygb-mediated NO formation were characterized. It was observed that Cygb-mediated NO generation increased linearly with the increase of Nitrite concentration under anaerobic conditions. This Cygb-mediated NO production greatly increased with acidosis and anoxia as occur in ischemic conditions. With the addition of Nitrite, soluble guanylyl cyclase (sGC) activation was significantly higher in normal smooth muscle cells compared to Cygb-knocked down cells with Cygb accounting for ~40% of the activation in control cells and ~60% in cells subjected to hypoxia for 48 hours. Overall, these studies show that Cygb-mediated Nitrite Reduction can play an important role in NO generation and sGC activation under hypoxic conditions, with this process regulated by pH, oxygen tension, Nitrite concentration, and the redox state of the cells.
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characterization of the magnitude and kinetics of xanthine oxidase catalyzed Nitrite Reduction evaluation of its role in nitric oxide generation in anoxic tissues
Journal of Biological Chemistry, 2001Co-Authors: Haitao Li, Alexandre Samouilov, Jay L ZweierAbstract:Abstract Xanthine oxidase (XO)-catalyzed Nitrite Reduction with nitric oxide (NO) production has been reported to occur under anaerobic conditions, but questions remain regarding the magnitude, kinetics, and biological importance of this process. To characterize this mechanism and its quantitative importance in biological systems, electron paramagnetic resonance spectroscopy, chemiluminescence NO analyzer, and NO electrode studies were performed. The XO reducing substrates xanthine, NADH, and 2,3-dihydroxybenz-aldehyde triggered Nitrite Reduction to NO, and the molybdenum-binding XO inhibitor oxypurinol inhibited this NO formation, indicating that Nitrite Reduction occurs at the molybdenum site. However, at higher xanthine concentrations, partial inhibition was seen, suggesting the formation of a substrate-bound reduced enzyme complex with xanthine blocking the molybdenum site. Studies of the pH dependence of NO formation indicated that XO-mediated Nitrite Reduction occurred via an acid-catalyzed mechanism. Nitrite and reducing substrate concentrations were important regulators of XO-catalyzed NO generation. The substrate dependence of anaerobic XO-catalyzed Nitrite Reduction followed Michaelis-Menten kinetics, enabling prediction of the magnitude of NO formation and delineation of the quantitative importance of this process in biological systems. It was determined that under conditions occurring during no-flow ischemia, myocardial XO and Nitrite levels are sufficient to generate NO levels comparable to those produced from nitric oxide synthase. Thus, XO-catalyzed Nitrite Reduction can be an important source of NO generation under ischemic conditions.
Tsuneo Hino - One of the best experts on this subject based on the ideXlab platform.
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Effect of ethanol on nitrate and Nitrite Reduction and methanogenesis in the ruminal microbiota
Animal Science Journal, 2005Co-Authors: Takahiro Yoshii, Narito Asanuma, Tsuneo HinoAbstract:The effect of ethanol on nitrate and Nitrite Reduction was examined by conducting in vitro experiments with mixed ruminal microbes. The addition of ethanol to cultures of mixed ruminal microbes stimulated nitrate Reduction, and, to a greater extent, Nitrite Reduction, which resulted in a decrease in Nitrite accumulation. However, known nitrate-reducing ruminal bacteria, such as Selenomonas ruminantium, Veillonella parvula and Wolinella succinogenes, were unable to utilize ethanol directly as an electron donor for nitrate Reduction. No nitrate-reducing bacterium capable of utilizing ethanol was found in the rumen of goats. However, when mixed ethanol-utilizing, hydrogen gas (H2)-producing bacteria (Ruminococcus albus and Ruminococcus flavefaciens) were added to the culture of the mixed nitrate-reducing bacteria described above, nitrate and Nitrite Reduction was observed. These results suggest that the nitrate-reducing bacteria utilized the H2 that was produced from ethanol oxidation by the ethanol-utilizing bacteria as an electron donor. It is conceivable that the stimulation of nitrate and Nitrite Reduction by ethanol, observed in the culture of mixed ruminal microbes, was a result of electron transfer from ethanol to nitrate, and Nitrite through H2, that is, ‘interspecies hydrogen transfer’ from ethanol-metabolizing bacteria to nitrate-reducing bacteria. Thus, the addition of ethanol to high-nitrate diets may be effective for preventing nitrate poisoning. Furthermore, methane production was reduced to less than one-third by the addition of mixed nitrate-reducing bacteria to the co-culture of mixed methanogens with mixed ethanol-utilizing bacteria incubated in a medium containing ethanol and nitrate. Therefore, the addition of ethanol and nitrate may decrease methanogenesis without suppressing overall fermentation in the rumen.
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Effects of pH and Electron Donors on Nitrate and Nitrite Reduction in Ruminal Microbiota
Nihon Chikusan Gakkaiho, 2001Co-Authors: Miwa Iwamoto, Narito Asanuma, Tsuneo HinoAbstract:Factors affecting nitrate and Nitrite Reduction in the rumen were examined. Nitrate and Nitrite Reduction by mixed microbes harvested from the goat rumen was increased by feeding a high-roughage diet, which contained a much higher amount of nitrate than concentrate. The activities of nitrate reductase and Nitrite reductase per bacterial mass appeared to be increased by feeding a high-nitrate diet, suggesting that these enzymes are induced by substrates. Nitrate and Nitrite Reduction was confirmed to be the fastest at neutral pH and affected by electron supply. The supplementation of electron donors, such as formate, H2, and lactate, stimulated nitrate and Nitrite Reduction, especially Nitrite Reduction, which decreased Nitrite accumulation. As a result, addition of formate or lactate in the presence of nitrate alleviated the inhibitory effect of Nitrite on fermentation, and greatly reduced methanogenesis.
Nadège Durban - One of the best experts on this subject based on the ideXlab platform.
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Nitrate and Nitrite Reduction activity of activated sludge microcosm in a highly alkaline environment with solid cementitious material
International Biodeterioration and Biodegradation, 2020Co-Authors: Nadège Durban, Vanessa Sonois-mazars, Pierre Albina, Alexandra Bertron, Achim Albrecht, Jean-charles Robinet, Benjamin ErableAbstract:Denitrification is a major biological process contributing to nitrate and Nitrite Reduction. However, this process remains poorly understood at alkaline pH although such conditions can be encountered in natural (e.g. soda lakes) or industrial environments (e.g. geological waste repositories with cementitious materials). To investigate the nitrate Reduction (NR) rate for pH > 9.5 in a cementitious environment, several batch reactors were implemented, with cement leachate or with hardened cement paste (HCP). In the experiments carried out with cement leachate, NR dropped from 0.72 mM/h at pH 9.5 to 0.17 mM/h at pH > 11, while the concentration of Nitrite increased. The NR was inhibited at pH close to 12, as was the Nitrite Reduction at pH above 11. In the reactor containing HCP, the NR rate was 0.75 mM/h at pH close to 10. Calcite precipitated on the HCP surface. Epifluorescence microscopy observations coupled with DNA labelling suggested the presence of microorganisms attached to the HCP surface. This was confirmed by biological growth coupled with NR activity after the transfer of the HCP into a new medium, considered to be sterile. The bacterial community analysis showed that the highly selective culture conditions led to the selection of two species: Halomonas sp. and a species known for its versatile metabolism and ability to form biofilms, i.e. Thauera sp.
José J. G. Moura - One of the best experts on this subject based on the ideXlab platform.
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Nitrite Reduction by molybdoenzymes: a new class of nitric oxide-forming Nitrite reductases
JBIC Journal of Biological Inorganic Chemistry, 2015Co-Authors: Luisa B. Maia, José J. G. MouraAbstract:Nitric oxide (NO) is a signalling molecule involved in several physiological processes, in both prokaryotes and eukaryotes, and Nitrite is being recognised as an NO source particularly relevant to cell signalling and survival under challenging conditions. The “non-respiratory” Nitrite Reduction to NO is carried out by “non-dedicated” Nitrite reductases, making use of metalloproteins present in cells to carry out other functions, such as several molybdoenzymes (a new class of nitric oxide-forming Nitrite reductases). This minireview will highlight the physiological relevance of molybdenum-dependent Nitrite-derived NO formation in mammalian, plant and bacterial signalling (and other) pathways. The mammalian xanthine oxidase/xanthine dehydrogenase, aldehyde oxidase, mitochondrial amidoxime-reducing component, plant nitrate reductase and bacterial aldehyde oxidoreductase and nitrate reductases will be considered. The Nitrite reductase activity of each molybdoenzyme will be described and the review will be oriented to discuss the feasibility of the reactions from a (bio)chemical point of view. In addition, the molecular mechanism proposed for the molybdenum-dependent Nitrite Reduction will be discussed in detail.
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Nitrite Reduction by xanthine oxidase family enzymes: a new class of Nitrite reductases.
Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry, 2010Co-Authors: Luisa B. Maia, José J. G. MouraAbstract:Mammalian xanthine oxidase (XO) and Desulfovibrio gigas aldehyde oxidoreductase (AOR) are members of the XO family of mononuclear molybdoenzymes that catalyse the oxidative hydroxylation of a wide range of aldehydes and heterocyclic compounds. Much less known is the XO ability to catalyse the Nitrite Reduction to nitric oxide radical (NO). To assess the competence of other XO family enzymes to catalyse the Nitrite Reduction and to shed some light onto the molecular mechanism of this reaction, we characterised the anaerobic XO- and AOR-catalysed Nitrite Reduction. The identification of NO as the reaction product was done with a NO-selective electrode and by electron paramagnetic resonance (EPR) spectroscopy. The steady-state kinetic characterisation corroborated the XO-catalysed Nitrite Reduction and demonstrated, for the first time, that the prokaryotic AOR does catalyse the Nitrite Reduction to NO, in the presence of any electron donor to the enzyme, substrate (aldehyde) or not (dithionite). Nitrite binding and Reduction was shown by EPR spectroscopy to occur on a reduced molybdenum centre. A molecular mechanism of AOR- and XO-catalysed Nitrite Reduction is discussed, in which the higher oxidation states of molybdenum seem to be involved in oxygen-atom insertion, whereas the lower oxidation states would favour oxygen-atom abstraction. Our results define a new catalytic performance for AOR—the Nitrite Reduction—and propose a new class of molybdenum-containing Nitrite reductases.