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1
Barat, R., J. Serralta, M. V. Ruano, E. Jiménez, J. Ribes, A. Seco y J. Ferrer. "Biological Nutrient Removal Model No. 2 (BNRM2): a general model for wastewater treatment plants". Water Science and Technology 67, n.º 7 (1 de abril de 2013): 1481–89. http://dx.doi.org/10.2166/wst.2013.004.
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This paper presents the plant-wide model Biological Nutrient Removal Model No. 2 (BNRM2). Since nitrite was not considered in the BNRM1, and this previous model also failed to accurately simulate the anaerobic digestion because precipitation processes were not considered, an extension of BNRM1 has been developed. This extension comprises all the components and processes required to simulate nitrogen removal via nitrite and the formation of the solids most likely to precipitate in anaerobic digesters. The solids considered in BNRM2 are: struvite, amorphous calcium phosphate, hidroxyapatite, newberite, vivianite, strengite, variscite, and calcium carbonate. With regard to nitrogen removal via nitrite, apart from nitrite oxidizing bacteria two groups of ammonium oxidizing organisms (AOO) have been considered since different sets of kinetic parameters have been reported for the AOO present in activated sludge systems and SHARON (Single reactor system for High activity Ammonium Removal Over Nitrite) reactors. Due to the new processes considered, BNRM2 allows an accurate prediction of wastewater treatment plant performance in wider environmental and operating conditions.
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Pijuan, M., L. Ye y Z. Yuan. "Could nitrite/free nitrous acid favour GAOs over PAOs in enhanced biological phosphorus removal systems?" Water Science and Technology 63, n.º 2 (1 de enero de 2011): 345–51. http://dx.doi.org/10.2166/wst.2011.062.
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Enhanced biological phosphorus removal (EBPR) normally occurs together with nitrogen removal in wastewater treatment plants (WWTPs). In recent years, efforts have been devoted to remove nitrogen via the nitrite pathway (oxidation of ammonia to nitrite and reduction of nitrite to nitrogen gas without going through nitrate), reducing the requirement for carbon and oxygen in the plant. However nitrite and free nitrous acid (FNA), the protonated species of nitrite, have been shown to cause EBPR deterioration under certain concentrations. This study provides a direct comparison between the different levels of FNA inhibition in the aerobic processes of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) by reviewing the studies published in this area. Also, new data is presented assessing the FNA effect on the anaerobic metabolism of these two groups of bacteria. Overall, FNA has shown inhibitory effects on most of the processes involved in the metabolism of PAOs and GAOs. However, the inhibition-initiation levels are different between different processes and, even more importantly between the two groups. In general, PAOs appear to be more affected than GAOs at the same level of FNA, thus giving GAOs competitive advantage over PAOs in EBPR systems when nitrite is present.
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Pambrun, V., E. Paul y M. Spérandio. "Treatment of nitrogen and phosphorus in highly concentrated effluent in SBR and SBBR processes". Water Science and Technology 50, n.º 6 (1 de septiembre de 2004): 269–76. http://dx.doi.org/10.2166/wst.2004.0385.
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Various sludge treatment processes produced supernatant with high ammonia concentration from 500 to 2,000 mgN/L and generally high phosphate concentration. Conversion of ammonia into nitrite via partial nitrification has proven to be an economic way, reducing oxygen and external COD requirements during the nitrification/denitrification process. Two processes with biomass retention are studied simultaneously: the sequencing batch reactor (SBR) and the sequencing batch biofilm reactor (SBBR). At a temperature of 30°C, the inhibition of nitrite-oxidizing bacteria due to high ammonia concentration has been studied in order to obtain a stable nitrite accumulation. This work has confirmed the effect of pH and dissolved oxygen on nitrite accumulation performance. During a two month starting period, both processes led to nitrite accumulation without nitrate production when pH was maintained above 7.5. From a 500 mgN/L effluent, the performance of the SBR, and the SBBR, reached respectively about 0.95gN-NO2−/gN-NH4+, and 0.4gN-NO2−/gN-NH4+. The SBBR appears to be more stable facing disturbances in dissolved oxygen conditions. Finally, the maximal phosphate removal rates obtained in the SBR reached 90%, and 70% in the SBBR, depending on ammonium accumulation in the reactor. Ammonium phosphate precipitation is likely to occur, as was suggested by crystals observation in the reactor.
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Guieysse, B., M. Plouviez, M. Coilhac y L. Cazali. "Nitrous oxide (N<sub>2</sub>O) production in axenic <i>Chlorella vulgaris</i> cultures: evidence, putative pathways, and potential environmental impacts". Biogeosciences Discussions 10, n.º 6 (17 de junio de 2013): 9739–63. http://dx.doi.org/10.5194/bgd-10-9739-2013.
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Abstract. Using antibiotic assays and genomic analysis, this study demonstrates nitrous oxide (N2O) is generated from axenic C. vulgaris cultures. In batch assays, this production is magnified under conditions favoring intracellular nitrite accumulation, but repressed when nitrate reductase (NR) activity is inhibited. These observations suggest N2O formation in C. vulgaris might proceed via NR-mediated nitrite reduction into nitric oxide (NO) acting as N2O precursor via a pathway similar to N2O formation in bacterial denitrifiers, although NO reduction to N2O under oxia remains unproven in plant cells. Alternatively, NR may reduce nitrite to nitroxyl (HNO), the latter being known to dimerize to N2O under oxia. Regardless of the precursor considered, an NR-mediated nitrite reduction pathway provides a unifying explanation for correlations reported between N2O emissions from algae-based ecosystems and NR activity, nitrate concentration, nitrite concentration, and photosynthesis repression. Moreover, these results indicate microalgae-mediated N2O formation might significantly contribute to N2O emissions in algae-based ecosystems. These findings have profound implications for the life cycle analysis of algae biotechnologies and our understanding of the global biogeochemical nitrogen cycle.
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Bristow, Laura A., Tage Dalsgaard, Laura Tiano, Daniel B. Mills, Anthony D. Bertagnolli, Jody J. Wright, Steven J. Hallam et al. "Ammonium and nitrite oxidation at nanomolar oxygen concentrations in oxygen minimum zone waters". Proceedings of the National Academy of Sciences 113, n.º 38 (6 de septiembre de 2016): 10601–6. http://dx.doi.org/10.1073/pnas.1600359113.
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A major percentage of fixed nitrogen (N) loss in the oceans occurs within nitrite-rich oxygen minimum zones (OMZs) via denitrification and anammox. It remains unclear to what extent ammonium and nitrite oxidation co-occur, either supplying or competing for substrates involved in nitrogen loss in the OMZ core. Assessment of the oxygen (O2) sensitivity of these processes down to the O2concentrations present in the OMZ core (<10 nmol⋅L−1) is therefore essential for understanding and modeling nitrogen loss in OMZs. We determined rates of ammonium and nitrite oxidation in the seasonal OMZ off Concepcion, Chile at manipulated O2levels between 5 nmol⋅L−1and 20 μmol⋅L−1. Rates of both processes were detectable in the low nanomolar range (5–33 nmol⋅L−1O2), but demonstrated a strong dependence on O2concentrations with apparent half-saturation constants (Kms) of 333 ± 130 nmol⋅L−1O2for ammonium oxidation and 778 ± 168 nmol⋅L−1O2for nitrite oxidation assuming one-component Michaelis–Menten kinetics. Nitrite oxidation rates, however, were better described with a two-component Michaelis–Menten model, indicating a high-affinity component with aKmof just a few nanomolar. As the communities of ammonium and nitrite oxidizers were similar to other OMZs, these kinetics should apply across OMZ systems. The high O2affinities imply that ammonium and nitrite oxidation can occur within the OMZ core whenever O2is supplied, for example, by episodic intrusions. These processes therefore compete with anammox and denitrification for ammonium and nitrite, thereby exerting an important control over nitrogen loss.
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Caballero, Antonio, Abraham Esteve-Núñez, Gerben J. Zylstra y Juan L. Ramos. "Assimilation of Nitrogen from Nitrite and Trinitrotoluene in Pseudomonas putida JLR11". Journal of Bacteriology 187, n.º 1 (1 de enero de 2005): 396–99. http://dx.doi.org/10.1128/jb.187.1.396-399.2005.
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ABSTRACT Pseudomonas putida JLR11 releases nitrogen from the 2,4,6-trinitrotoluene (TNT) ring as nitrite or ammonium. These processes can occur simultaneously, as shown by the observation that a nasB mutant impaired in the reduction of nitrite to ammonium grew at a slower rate than the parental strain. Nitrogen from TNT is assimilated via the glutamine syntethase-glutamate synthase (GS-GOGAT) pathway, as evidenced by the inability of GOGAT mutants to use TNT. This pathway is also used to assimilate ammonium from reduced nitrate and nitrite. Three mutants that had insertions in ntrC, nasT, and cnmA, which encode regulatory proteins, failed to grow on nitrite but grew on TNT, although slower than the wild type.
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Guieysse, B., M. Plouviez, M. Coilhac y L. Cazali. "Nitrous Oxide (N<sub>2</sub>O) production in axenic <i>Chlorella vulgaris</i> microalgae cultures: evidence, putative pathways, and potential environmental impacts". Biogeosciences 10, n.º 10 (25 de octubre de 2013): 6737–46. http://dx.doi.org/10.5194/bg-10-6737-2013.
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Abstract. Using antibiotic assays and genomic analysis, this study demonstrates nitrous oxide (N2O) is generated from axenic Chlorella vulgaris cultures. In batch assays, this production is magnified under conditions favouring intracellular nitrite accumulation, but repressed when nitrate reductase (NR) activity is inhibited. These observations suggest N2O formation in C. vulgaris might proceed via NR-mediated nitrite reduction into nitric oxide (NO) acting as N2O precursor via a pathway similar to N2O formation in bacterial denitrifiers, although NO reduction to N2O under oxia remains unproven in plant cells. Alternatively, NR may reduce nitrite to nitroxyl (HNO), the latter being known to dimerize to N2O under oxia. Regardless of the precursor considered, an NR-mediated nitrite reduction pathway provides a unifying explanation for correlations reported between N2O emissions from algae-based ecosystems and NR activity, nitrate concentration, nitrite concentration, and photosynthesis repression. Moreover, these results indicate microalgae-mediated N2O formation might significantly contribute to N2O emissions in algae-based ecosystems (e.g. 1.38–10.1 kg N2O-N ha−1 yr−1 in a 0.25 m deep raceway pond operated under Mediterranean climatic conditions). These findings have profound implications for the life cycle analysis of algae biotechnologies and our understanding of the global biogeochemical nitrogen cycle.
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Mascarenhas, Romila, Zhu Li, Carmen Gherasim, Markus Ruetz y Ruma Banerjee. "The human B12 trafficking protein CblC processes nitrocobalamin". Journal of Biological Chemistry 295, n.º 28 (26 de mayo de 2020): 9630–40. http://dx.doi.org/10.1074/jbc.ra120.014094.
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In humans, cobalamin or vitamin B12 is delivered to two target enzymes via a complex intracellular trafficking pathway comprising transporters and chaperones. CblC (or MMACHC) is a processing chaperone that catalyzes an early step in this trafficking pathway. CblC removes the upper axial ligand of cobalamin derivatives, forming an intermediate in the pathway that is subsequently converted to the active cofactor derivatives. Mutations in the cblC gene lead to methylmalonic aciduria and homocystinuria. Here, we report that nitrosylcobalamin (NOCbl), which was developed as an antiproliferative reagent, and is purported to cause cell death by virtue of releasing nitric oxide, is highly unstable in air and is rapidly oxidized to nitrocobalamin (NO2Cbl). We demonstrate that CblC catalyzes the GSH-dependent denitration of NO2Cbl forming 5-coordinate cob(II)alamin, which had one of two fates. It could be oxidized to aquo-cob(III)alamin or enter a futile thiol oxidase cycle forming GSH disulfide. Arg-161 in the active site of CblC suppressed the NO2Cbl-dependent thiol oxidase activity, whereas the disease-associated R161G variant stabilized cob(II)alamin and promoted futile cycling. We also report that CblC exhibits nitrite reductase activity, converting cob(I)alamin and nitrite to NOCbl. Finally, the denitration activity of CblC supported cell proliferation in the presence of NO2Cbl, which can serve as a cobalamin source. The newly described nitrite reductase and denitration activities of CblC extend its catalytic versatility, adding to its known decyanation and dealkylation activities. In summary, upon exposure to air, NOCbl is rapidly converted to NO2Cbl, which is a substrate for the B12 trafficking enzyme CblC.
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Jacob, Juliane, Tina Sanders y Kirstin Dähnke. "Nitrite consumption and associated isotope changes during a river flood event". Biogeosciences 13, n.º 19 (11 de octubre de 2016): 5649–59. http://dx.doi.org/10.5194/bg-13-5649-2016.
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Abstract. In oceans, estuaries, and rivers, nitrification is an important nitrate source, and stable isotopes of nitrate are often used to investigate recycling processes (e.g. remineralisation, nitrification) in the water column. Nitrification is a two-step process, where ammonia is oxidised via nitrite to nitrate. Nitrite usually does not accumulate in natural environments, which makes it difficult to study the single isotope effect of ammonia oxidation or nitrite oxidation in natural systems. However, during an exceptional flood in the Elbe River in June 2013, we found a unique co-occurrence of ammonium, nitrite, and nitrate in the water column, returning towards normal summer conditions within 1 week. Over the course of the flood, we analysed the evolution of δ15N–NH4+ and δ15N–NO2− in the Elbe River. In concert with changes in suspended particulate matter (SPM) and δ15N SPM, as well as nitrate concentration, δ15N–NO3− and δ18O–NO3−, we calculated apparent isotope effects during net nitrite and nitrate consumption. During the flood event, > 97 % of total reactive nitrogen was nitrate, which was leached from the catchment area and appeared to be subject to assimilation. Ammonium and nitrite concentrations increased to 3.4 and 4.4 µmol L−1, respectively, likely due to remineralisation, nitrification, and denitrification in the water column. δ15N–NH4+ values increased up to 12 ‰, and δ15N–NO2− ranged from −8.0 to −14.2 ‰. Based on this, we calculated an apparent isotope effect 15ε of −10.0 ± 0.1 ‰ during net nitrite consumption, as well as an isotope effect 15ε of −4.0 ± 0.1 ‰ and 18ε of −5.3 ± 0.1 ‰ during net nitrate consumption. On the basis of the observed nitrite isotope changes, we evaluated different nitrite uptake processes in a simple box model. We found that a regime of combined riparian denitrification and 22 to 36 % nitrification fits best with measured data for the nitrite concentration decrease and isotope increase.
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Alvarino, Teresa, Evina Katsou, Simos Malamis, Sonia Suarez, Francisco Omil y Francesco Fatone. "Inhibition of biomass activity in the via nitrite nitrogen removal processes by veterinary pharmaceuticals". Bioresource Technology 152 (enero de 2014): 477–83. http://dx.doi.org/10.1016/j.biortech.2013.10.107.
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Zeng, R. J., R. Lemaire, Z. Yuan y J. Keller. "A novel wastewater treatment process: simultaneous nitrification, denitrification and phosphorus removal". Water Science and Technology 50, n.º 10 (1 de noviembre de 2004): 163–70. http://dx.doi.org/10.2166/wst.2004.0635.
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Simultaneous nitrification and denitrification (SND) via the nitrite pathway and anaerobic–anoxic enhanced biological phosphorus removal (EBPR) are two processes that can significantly reduce the COD demand for nitrogen and phosphorus removal. The combination of these two processes has the potential of achieving simultaneous nitrogen and phosphorus removal with a minimal requirement for COD. A lab-scale sequencing batch reactor (SBR) was operated in alternating anaerobic–aerobic mode with a low dissolved oxygen concentration (DO, 0.5 mg/L) during the aerobic period, and was demonstrated to accomplish nitrification, denitrification and phosphorus removal. Under anaerobic conditions, COD was taken up and converted to polyhydroxyalkanoates (PHA), accompanied with phosphorus release. In the subsequent aerobic stage, PHA was oxidized and phosphorus was taken up to less than 0.5 mg/L at the end of the cycle. Ammonia was also oxidised during the aerobic period, but without accumulation of nitrite or nitrate in the system, indicating the occurrence of simultaneous nitrification and denitrification. However, off-gas analysis found that the final denitrification product was mainly nitrous oxide (N2O) not N2. Further experimental results demonstrated that nitrogen removal was via nitrite, not nitrate. These experiments also showed that denitrifying glycogen-accumulating organisms rather than denitrifying polyphosphate-accumulating organisms were responsible for the denitrification activity.
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Nakano, Michiko M., Tamara Hoffmann, Yi Zhu y Dieter Jahn. "Nitrogen and Oxygen Regulation of Bacillus subtilis nasDEF Encoding NADH-Dependent Nitrite Reductase by TnrA and ResDE". Journal of Bacteriology 180, n.º 20 (15 de octubre de 1998): 5344–50. http://dx.doi.org/10.1128/jb.180.20.5344-5350.1998.
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ABSTRACT The nitrate and nitrite reductases of Bacillus subtilishave two different physiological functions. Under conditions of nitrogen limitation, these enzymes catalyze the reduction of nitrate via nitrite to ammonia for the anabolic incorporation of nitrogen into biomolecules. They also function catabolically in anaerobic respiration, which involves the use of nitrate and nitrite as terminal electron acceptors. Two distinct nitrate reductases, encoded bynarGHI and nasBC, function in anabolic and catabolic nitrogen metabolism, respectively. However, as reported herein, a single NADH-dependent, soluble nitrite reductase encoded by the nasDE genes is required for both catabolic and anabolic processes. The nasDE genes, together with nasBC(encoding assimilatory nitrate reductase) and nasF(required for nitrite reductase siroheme cofactor formation), constitute the nas operon. Data presented show that transcription of nasDEF is driven not only by the previously characterized nas operon promoter but also from an internal promoter residing between the nasC andnasD genes. Transcription from both promoters is activated by nitrogen limitation during aerobic growth by the nitrogen regulator, TnrA. However, under conditions of oxygen limitation,nasDEF expression and nitrite reductase activity were significantly induced. Anaerobic induction of nasDEFrequired the ResDE two-component regulatory system and the presence of nitrite, indicating partial coregulation of NasDEF with the respiratory nitrate reductase NarGHI during nitrate respiration.
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Shi, Shun y Wendong Tao. "Numerical modeling of nitrogen removal processes in biofilters with simultaneous nitritation and anammox". Water Science and Technology 67, n.º 3 (1 de febrero de 2013): 549–56. http://dx.doi.org/10.2166/wst.2012.594.
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This study developed a simple numerical model for nitrogen removal in biofilters, which was designed to enhance simultaneous nitritation and anaerobic ammonium oxidation (anammox). It is the first attempt to simulate anammox together with two-step nitrification in natural treatment systems, which may have different kinetic parameters and temperature effects from conventional bioreactors. Prediction accuracy was improved by adjusting kinetic coefficients over the startup period of the biofilters. The maximum rates of nitritation and nitrite oxidation increased linearly over time during the startup period. Simulations confirmed successful enhancement of simultaneous nitritation and anammox (SNA) in the biofilters, with anammox contributing 35% of ammonium removal. Effluent ammonium concentration was affected by influent ammonium concentration and the maximum nitritation rate, and was insensitive to the maximum nitrite oxidation rate and anammox substrate factor. Ammonium removal via SNA was likely limited by biomass of aerobic ammonia oxidizing bacteria in the biofilters. The developed model is a promising tool for studying the dynamics of nitrogen removal processes including SNA in natural treatment systems.
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Gibbs, B. M., L. R. Shephard, K. A. Third y R. Cord-Ruwisch. "The presence of ammonium facilitates nitrite reduction under PHB driven simultaneous nitrification and denitrification". Water Science and Technology 50, n.º 10 (1 de noviembre de 2004): 181–88. http://dx.doi.org/10.2166/wst.2004.0639.
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For economic and efficient nitrogen removal from wastewater treatment plants via simultaneous nitrification and denitrification the nitrification process should stop at the level of nitrite such that nitrite rather than nitrate becomes the substrate for denitrification. This study aims to contribute to the understanding of the conditions that are necessary to improve nitrite reduction over nitrite oxidation. Laboratory sequencing batch reactors (SBRs) were operated with synthetic wastewater containing acetate as COD and ammonium as the nitrogen source. Computer controlled operation of the reactors allowed reproducible simultaneous nitrification and denitrification (SND). The oxygen supply was kept precisely at a low level of 0.5 mgL−1 and bacterial PHB was the only electron donor available for denitrification. During SND little nitrite or nitrate accumulated (< 20% total N), indicating that the reducing processes were almost as fast as the production of nitrite and nitrate from nitrification. Nitrite spiking tests were performed to investigate the fate of nitrite under different oxidation (0.1–1.5 mgL−1 of dissolved oxygen) and reduction conditions. High levels of reducing power were provided by allowing the cells to build up to 2.5 mM of PHB. Nitrite added was preferentially oxidised to nitrate rather than reduced even when dissolved oxygen was low and reducing power (PHB) was excessively high. However, the presence of ammonium enabled significant reduction of nitrite under low oxygen conditions. This is consistent with previous observations in SBR where aerobic nitrite and nitrate reduction occurred only as long as ammonium was present. As soon as ammonium was depleted, the rate of denitrification decreased significantly. The significance of the observed strongly stimulating effect of ammonium on nitrite reduction under SND conditions is discussed and potential consequences for SBR operation are suggested.
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Al-Omari, Ahmed, Bernhard Wett, Ingmar Nopens, Haydee De Clippeleir, Mofei Han, Pusker Regmi, Charles Bott y Sudhir Murthy. "Model-based evaluation of mechanisms and benefits of mainstream shortcut nitrogen removal processes". Water Science and Technology 71, n.º 6 (22 de enero de 2015): 840–47. http://dx.doi.org/10.2166/wst.2015.022.
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The main challenge in implementing shortcut nitrogen removal processes for mainstream wastewater treatment is the out-selection of nitrite oxidizing bacteria (NOB) to limit nitrate production. A model-based approach was utilized to simulate the impact of individual features of process control strategies to achieve NO−2-N shunt via NOB out-selection. Simulations were conducted using a two-step nitrogen removal model from the literature. Nitrogen shortcut removal processes from two case studies were modeled to illustrate the contribution of NOB out-selection mechanisms. The paper highlights a comparison between two control schemes; one was based on online measured ammonia and the other was based on a target ratio of 1 for ammonia vs. NOx (nitrate + nitrite) (AVN). Results indicated that the AVN controller possesses unique features to nitrify only that amount of nitrogen that can be denitrified, which promotes better management of incoming organics and bicarbonate for a more efficient NOB out-selection. Finally, the model was used in a scenario analysis, simulating hypothetical optimized performance of the pilot process. An estimated potential saving of 60% in carbon addition for nitrogen removal by implementing full-scale mainstream deammonification was predicted.
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Rols, J. L., M. Mauret, H. Rahmani, K. M. Nguyen, B. Capdeville, J. C. Cornier y A. Deguin. "Population Dynamics and Nitrite Build-Up in Activated Sludge and Biofilm Processes for Nitrogen Removal". Water Science and Technology 29, n.º 7 (1 de abril de 1994): 43–51. http://dx.doi.org/10.2166/wst.1994.0301.
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This article has the objective of showing the cause effect relationship between the dynamics of growth of autotrophic populations involved in nitrification and the uncontrolled accumulation of nitrite ions. This accumulation results in a disequilibrium in number or viability between the genera Nitrosomonas and Nicrobacter. This disequilibrium can be imposed, for example, by an inhibition of the activity of the genus Nitrobacter linked to the presence of free ammonia in the environment. The threshold of inhibition and the resultant degree of accumulation of nitrite depend both on the history of the sludge utilised as inoculum (mixed autotrophic population or enriched in one of two sources) and on the hydraulic regime of the reactor (completely mixed reactor for the activated sludges and piston reactor for the fixed cultures). These results enable us to better understand the behaviour of a nitrification reactor and to propose solutions either to avoid the accumulation of nitrites or to intensify this accumulation with the goal of proposing a new process of nitritation-denitritation via the nitrites route (nitrates shunt).
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Huang, S. y P. R. Jaffé. "Characterization of incubation experiments and development of an enrichment culture capable of ammonium oxidation under iron-reducing conditions". Biogeosciences 12, n.º 3 (10 de febrero de 2015): 769–79. http://dx.doi.org/10.5194/bg-12-769-2015.
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Abstract. Incubation experiments were conducted using soil samples from a forested riparian wetland where we have previously observed anaerobic ammonium oxidation coupled to iron reduction. Production of both nitrite and ferrous iron was measured repeatedly during incubations when the soil slurry was supplied with either ferrihydrite or goethite and ammonium chloride. Significant changes in the microbial community were observed after 180 days of incubation as well as in a continuous flow membrane reactor, using 16S rRNA gene PCR-denaturing gradient gel electrophoresis, 454 pyrosequencing, and real-time quantitative PCR analysis. We be Acidimicrobiaceae bacterium A6), belonging to the Acidimicrobiaceae family, whose closest cultivated relative is Ferrimicrobium acidiphilum (with 92% identity) and Acidimicrobium ferrooxidans (with 90% identity), might play a key role in this anaerobic biological process that uses ferric iron as an electron acceptor while oxidizing ammonium to nitrite. After ammonium was oxidized to nitrite, nitrogen loss proceeded via denitrification and/or anammox.
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Huang, S. y P. R. Jaffé. "Characterization of incubation experiments and development of an enrichment culture capable of ammonium oxidation under iron reducing conditions". Biogeosciences Discussions 11, n.º 8 (14 de agosto de 2014): 12295–321. http://dx.doi.org/10.5194/bgd-11-12295-2014.
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Abstract. Incubation experiments were conducted using soil samples from a forested riparian wetland where we have previously observed anaerobic ammonium oxidation coupled to iron reduction. Production of both nitrite and ferrous iron were measured repeatedly during incubations when the soil slurry was supplied with either ferrihydrite or goethite and ammonium chloride. Significant changes in the microbial community were observed after 180 days of incubation as well as in a continuous flow membrane reactor, using 16S rRNA gene PCR-denaturing gradient gel electrophoresis, 454-pyrosequencing, and real-time quantitative PCR analysis. We believe that one of the dominant microbial species in our system (an uncultured Acidimicrobiaceae bacterium A6), belonging to the Acidimicrobiaceae family, whose closest cultivated relative is Ferrimicrobium acidiphilum (with 92% identity) and Acidimicrobium ferrooxidans (with 90% identity), might play a key role in this anaerobic biological process that uses ferric iron as an electron acceptor while oxidizing ammonium to nitrite. After ammonium was oxidized to nitrite, nitrogen loss proceeded via denitrification and/or anammox.
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Ji, Qixing, Claudia Frey, Xin Sun, Melanie Jackson, Yea-Shine Lee, Amal Jayakumar, Jeffrey C. Cornwell y Bess B. Ward. "Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay". Biogeosciences 15, n.º 20 (18 de octubre de 2018): 6127–38. http://dx.doi.org/10.5194/bg-15-6127-2018.
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Abstract. Nitrous oxide (N2O) is a greenhouse gas and an ozone depletion agent. Estuaries that are subject to seasonal anoxia are generally regarded as N2O sources. However, insufficient understanding of the environmental controls on N2O production results in large uncertainty about the estuarine contribution to the global N2O budget. Incubation experiments with nitrogen stable isotope tracer were used to investigate the geochemical factors controlling N2O production from denitrification in the Chesapeake Bay, the largest estuary in North America. The highest potential rates of water column N2O production via denitrification (7.5±1.2 nmol-N L−1 h−1) were detected during summer anoxia, during which oxidized nitrogen species (nitrate and nitrite) were absent from the water column. At the top of the anoxic layer, N2O production from denitrification was stimulated by addition of nitrate and nitrite. The relative contribution of nitrate and nitrite to N2O production was positively correlated with the ratio of nitrate to nitrite concentrations. Increased oxygen availability, up to 7 µmol L−1 oxygen, inhibited both N2O production and the reduction of nitrate to nitrite. In spring, high oxygen and low abundance of denitrifying microbes resulted in undetectable N2O production from denitrification. Thus, decreasing the nitrogen input into the Chesapeake Bay has two potential impacts on the N2O production: a lower availability of nitrogen substrates may mitigate short-term N2O emissions during summer anoxia; and, in the long-run (timescale of years), eutrophication will be alleviated and subsequent reoxygenation of the bay will further inhibit N2O production.
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Humbert, Guillaume, Mathieu Sébilo, Justine Fiat, Longqi Lang, Ahlem Filali, Véronique Vaury, Mathieu Spérandio y Anniet M. Laverman. "Isotopic evidence for alteration of nitrous oxide emissions and producing pathways' contribution under nitrifying conditions". Biogeosciences 17, n.º 4 (24 de febrero de 2020): 979–93. http://dx.doi.org/10.5194/bg-17-979-2020.
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Abstract. Nitrous oxide (N2O) emissions from a nitrifying biofilm reactor were investigated with N2O isotopocules. The nitrogen isotopomer site preference of N2O (15N-SP) indicated the contribution of producing and consuming pathways in response to changes in oxygenation level (from 0 % to 21 % O2 in the gas mix), temperature (from 13.5 to 22.3 ∘C) and ammonium concentrations (from 6.2 to 62.1 mg N L−1). Nitrite reduction, either nitrifier denitrification or heterotrophic denitrification, was the main N2O-producing pathway under the tested conditions. Difference between oxidative and reductive rates of nitrite consumption was discussed in relation to NO2- concentrations and N2O emissions. Hence, nitrite oxidation rates seem to decrease as compared to ammonium oxidation rates at temperatures above 20 ∘C and under oxygen-depleted atmosphere, increasing N2O production by the nitrite reduction pathway. Below 20 ∘C, a difference in temperature sensitivity between hydroxylamine and ammonium oxidation rates is most likely responsible for an increase in N2O production via the hydroxylamine oxidation pathway (nitrification). A negative correlation between the reaction kinetics and the apparent isotope fractionation was additionally shown from the variations of δ15N and δ18O values of N2O produced from ammonium. The approach and results obtained here, for a nitrifying biofilm reactor under variable environmental conditions, should allow for application and extrapolation of N2O emissions from other systems such as lakes, soils and sediments.
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Wiercik, Paweł, Magdalena Domańska y Tomasz Konieczny. "Nitrogen recovery from reject water by production of nitrite concentrate via nitritation, membrane processes and ion exchange". DESALINATION AND WATER TREATMENT 197 (2020): 90–100. http://dx.doi.org/10.5004/dwt.2020.25986.
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Park, Ji-Won, Barbora Piknova, Khanh Nghiem, Jay N. Lozier y Alan N. Schechter. "Thrombelastographic Demonstration of Nitrite Inhibition of Platelet Function". Blood 120, n.º 21 (16 de noviembre de 2012): 5148. http://dx.doi.org/10.1182/blood.v120.21.5148.5148.
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Abstract Abstract 5148 We have recently shown that nitrite ions in blood will inhibit platelet aggregation and activation as measured by aggregometry and flow cytometric analysis of P-selectin under partially deoxygenated conditions. We now show that these phenomena can be measured by thrombelastographic analysis, an alternative method which supplies additional parameters of clotting, using whole blood from healthy donors. Nitric oxide (NO) can be generated by endogenous nitric oxide synthase (NOS) as well as by a serial reduction pathway in which nitrate and nitrite are converted to NO via several enzymatic and nonenzymatic mechanisms. We have previously shown that nitrite anions at 0. 1μM inhibit platelet activation and aggregation in the presence of red blood cells through their reduction to NO and this effect was enhanced by deoxygenation. In the present study, we examined the influence of nitrite on the clotting properties of blood to investigate how nitrite may affect overall clotting processes by modulating platelet function. We measured major clotting parameters such as reaction time (R, minute of initial fibrin formation), angle (velocity of clot growth), and maximum amplitude (MA, clot strength) using thrombelastograph hemostasis analyzer (TEG5000®) in whole blood diluted with plasma to yield 20% Hct. Both the NO donor (DEANONOate) and nitrite showed inhibitory effects on clotting parameters resulting in delayed R, decreased angle, and reduced MA in a dose dependent manner. However, the sources of NO did not change any TEG parameters in plasma. These results suggest that this new clinical method may be used to follow NO inhibition of platelet-induced blood clotting and that the physiological effect of factors which determine NO bioavailability, such as endogenous levels of blood and tissue nitrite, could be used as biomarkers for predicting hemostatic potential. Disclosures: Schechter: NIH: Employment, co-inventor of NIH patent on use of nitrite in disease, co-inventor of NIH patent on use of nitrite in disease Patents & Royalties.
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Helmer, C., C. Tromm, A. Hippen, K. H. Rosenwinkel, C. F. Seyfried y S. Kunst. "Single stage biological nitrogen removal by nitritation and anaerobic ammonium oxidation in biofilm systems". Water Science and Technology 43, n.º 1 (1 de enero de 2001): 311–20. http://dx.doi.org/10.2166/wst.2001.0062.
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In full scale wastewater treatment plants with at times considerable deficits in the nitrogen balances, it could hitherto not be sufficiently explained which reactions are the cause of the nitrogen losses and which micro-organisms participate in the process. The single stage conversion of ammonium into gaseous end-products – which is henceforth referred to as deammonification – occurs particularly frequently in biofilm systems. In the meantime, one has succeeded to establish the deammonification processes in a continuous flow moving-bed pilot plant. In batch tests with the biofilm covered carriers, it was possible for the first time to examine the nitrogen conversion at the intact biofilm. Depending on the dissolved oxygen (DO) concentration, two autotrophic nitrogen converting reactions in the biofilm could be proven: one nitritation process under aerobic conditions and one anaerobic ammonium oxidation. With the anaerobic ammonium oxidation, ammonium as electron donor was converted with nitrite aselectron acceptor. The end-product of this reaction was N2. Ammonium and nitrite did react in a stoichiometrical ratio of 1:1.37, a ratio which has in the very same dimension been described for the ANAMMOX-process (1:1.31±0.06). Via the oxygen concentration in the surrounding medium, it was possible to control the ratio of nitritation and anaerobic ammonium oxidation in the nitrogen conversion of the biofilm. Both processes were evenly balanced at a DO concentration of 0.7 mg/l, so that it was possible to achieve a direct, almost complete elimination of ammonium without addition of nitrite. One part of the provided ammonium did participate in the nitritation, the other in the anaerobic ammonium oxidation. Through the aerobic ammonium oxidation into nitrite within the outer oxygen supplied layers of the biofilm, the reaction partner was produced for the anaerobic ammonium oxidation within the inner layers of the biofilm.
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Dähnke, Kirstin, Tina Sanders, Yoana Voynova y Scott D. Wankel. "Nitrogen isotopes reveal a particulate-matter-driven biogeochemical reactor in a temperate estuary". Biogeosciences 19, n.º 24 (21 de diciembre de 2022): 5879–91. http://dx.doi.org/10.5194/bg-19-5879-2022.
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Abstract. Estuaries and rivers are important biogeochemical reactors that act to modify the loads and composition of nutrients in the coastal zone. In a case study during July 2013, we sampled an 80 km transect along the Elbe Estuary under low-oxygen conditions. To better elucidate specific mechanisms of estuarine nitrogen processing, we tracked the evolution of the stable isotopic composition of nitrate, nitrite, particulate matter, and ammonium through the water column. This approach allowed assessment of the in situ isotope effects of ammonium and nitrite oxidation and of remineralization at the reach scale. The isotope effects of nitrite oxidation and ammonium oxidation were consistent with pure-culture assessments. We found that the nitrogen budget of the Elbe Estuary is governed by settling, resuspension, and remineralization of particulate matter, and we further used our stable isotope data to evaluate sources and sinks of nitrogen in the Elbe Estuary via an isotope mass-balance approach. We find that the reactivity of particulate matter, through its remineralization in the estuary, is the main control on the isotope dynamics of inorganic nitrogen species. Moreover, while underscoring this role of particulate matter delivery and reactivity, the isotope mass balance also indicated additional sinks of reactive nitrogen, such as possible denitrification of water column nitrate in the intensively dredged and deep Hamburg Harbor region.
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Hou, Lei, Xiabing Xie, Xianhui Wan, Shuh-Ji Kao, Nianzhi Jiao y Yao Zhang. "Niche differentiation of ammonia and nitrite oxidizers along a salinity gradient from the Pearl River estuary to the South China Sea". Biogeosciences 15, n.º 16 (29 de agosto de 2018): 5169–87. http://dx.doi.org/10.5194/bg-15-5169-2018.
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Abstract. The niche differentiation of ammonia and nitrite oxidizers is controversial because they display disparate patterns in estuarine, coastal, and oceanic regimes. We analyzed diversity and abundance of ammonia-oxidizing archaea (AOA) and β-proteobacteria (AOB), nitrite-oxidizing bacteria (NOB), and nitrification rates to identify their niche differentiation along a salinity gradient from the Pearl River estuary to the South China Sea. AOA were generally more abundant than β-AOB; however, AOB more clearly attached to particles compared with AOA in the upper reaches of the Pearl River estuary. The NOB Nitrospira had higher abundances in the upper and middle reaches of the Pearl River estuary, while Nitrospina was dominant in the lower estuary. In addition, AOB and Nitrospira could be more active than AOA and Nitrospina since significantly positive correlations were observed between their gene abundance and the nitrification rate in the Pearl River estuary. There is a significant positive correlation between ammonia and nitrite oxidizer abundances in the hypoxic waters of the estuary, suggesting a possible coupling through metabolic interactions between them. Phylogenetic analysis further revealed that the AOA and NOB Nitrospina subgroups can be separated into different niches based on their adaptations to substrate levels. Water mass mixing is apparently crucial in regulating the distribution of nitrifiers from the estuary to open ocean. However, when eliminating water mass effect, the substrate availability and the nitrifiers' adaptations to substrate availability via their ecological strategies essentially determine their niche differentiation.
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Petit, Gaëlle, Gina Villamonte, Marie de Lamballerie y Vanessa Jury. "Comparing Innovative Versus Conventional Ham Processes via Environmental Life Cycle Assessment Supplemented with the Assessment of Nitrite Impacts on Human Health". Applied Sciences 11, n.º 1 (5 de enero de 2021): 451. http://dx.doi.org/10.3390/app11010451.
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Global sustainability indicators, particularly in human health, are necessary to describe agrifood products footprint. Nitrosamines are toxic molecules that are often encountered in cured and processed meats. As they are frequently consumed, meat-based products need to be assessed to evaluate their potential impact on human health. This article provides a methodological framework based on life cycle assessment for comparing meat product processing scenarios. The respective contributions of each step of the product life cycle are extended with a new human health indicator, nitrosamine toxicity, which has not been previously included in life cycle assessment (LCA) studies and tools (software and databases). This inclusion allows for the comparison of conventional versus innovative processes. Nitrosamines toxicity was estimated to be 2.20x10−6 disability-adjusted life years (DALY) for 1 kg of consumed conventional cooked ham while 4.54x10−7 DALY for 1 kg of consumed innovative cooked ham. The potential carcinogenic and noncarcinogenic effects of nitrosamines from meat products on human health are taken into account. Human health indicators are an important step forward in the comprehensive application of LCA methodology to improve the global sustainability of food systems.
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Marino, Marco, Hugo Cruz Ramos, Tamara Hoffmann, Philippe Glaser y Dieter Jahn. "Modulation of Anaerobic Energy Metabolism of Bacillus subtilis by arfM(ywiD)". Journal of Bacteriology 183, n.º 23 (1 de diciembre de 2001): 6815–21. http://dx.doi.org/10.1128/jb.183.23.6815-6821.2001.
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ABSTRACT Bacillus subtilis grows under anaerobic conditions utilizing nitrate ammonification and various fermentative processes. The two-component regulatory system ResDE and the redox regulator Fnr are the currently known parts of the regulatory system for anaerobic adaptation. Mutation of the open reading frame ywiDlocated upstream of the respiratory nitrate reductase operonnarGHJI resulted in elimination of the contribution of nitrite dissimilation to anaerobic nitrate respiratory growth. Significantly reduced nitrite reductase (NasDE) activity was detected, while respiratory nitrate reductase activity was unchanged. Anaerobic induction of nasDE expression was found to be significantly dependent on intact ywiD, while anaerobicnarGHJI expression was ywiD independent. Anaerobic transcription of hmp, encoding a flavohemoglobin-like protein, and of the fermentative operonslctEP and alsSD, responsible for lactate and acetoin formation, was partially dependent on ywiD. Expression of pta, encoding phosphotransacetylase involved in fermentative acetate formation, was not influenced byywiD. Transcription of the ywiD gene was anaerobically induced by the redox regulator Fnr via the conserved Fnr-box (TGTGA-6N-TCACT) centered 40.5 bp upstream of the transcriptional start site. Anaerobic induction of ywiDby resDE was found to be indirect viaresDE-dependent activation of fnr. TheywiD gene is subject to autorepression and nitrite repression. These results suggest a ResDE → Fnr → YwiD regulatory cascade for the modulation of genes involved in the anaerobic metabolism of B. subtilis. Therefore,ywiD was renamed arfM for anaerobic respiration and fermentation modulator.
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MURPHY, Colin y Philip NEWSHOLME. "Importance of glutamine metabolism in murine macrophages and human monocytes to L-arginine biosynthesis and rates of nitrite or urea production". Clinical Science 95, n.º 4 (1 de octubre de 1998): 397–407. http://dx.doi.org/10.1042/cs0950397.
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1.The intermediates of biochemical cycles are commonly utilized for biosynthetic processes; thus at least one intermediate must be replenished de novo to provide constant flux through the cycle. The utilization of l-arginine for NO synthesis in macrophages may thus reduce the concentration of intermediates of the urea cycle. It is possible that a glutamine-utilizing pathway exists in mononuclear phagocytes that may connect with the urea cycle. 2.In this paper we report that mouse peritoneal resident and Bacillus Calmette–Guerin (BCG)-activated macrophages and human monocytes are capable of utilizing glutamine at high rates, contain sufficient activity of the enzymes required to convert glutamine to citrulline (and subsequently citrulline to arginine) to account for observed rates of nitrite synthesis in the absence of extracellular l-arginine, and will release nitrite when exposed to intermediates of the proposed glutamine → arginine pathway. 3.The rate of nitrite production (in the absence of extracellular arginine) was reduced by culturing macrophages or monocytes in the presence of the glutaminase inhibitor 6-diazo 5-oxo norleucine. 4.The rate and extent of arginase secretion, glutamine utilization, nitrite production (basal and lipopolysaccharide-stimulated) and phosphate-dependent glutaminase activity from BCG-activated macrophages was increased compared with resident cells. 5.We suggest that the elevated arginase secretion rates in activated macrophages would effectively increase the intracellular concentration of arginine available for conversion to NO via inducible nitric oxide synthase, the expression of which is known to increase on activation of macrophages or monocytes. Additionally, the rate of l-arginine biosynthesis from glutamine may be increased on immunostimulation of the macrophage.
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Miller, Robert B., Kenton Lawson, Anwar Sadek, Chelsea N. Monty y John M. Senko. "Uniform and Pitting Corrosion of Carbon Steel byShewanella oneidensisMR-1 under Nitrate-Reducing Conditions". Applied and Environmental Microbiology 84, n.º 12 (13 de abril de 2018): e00790-18. http://dx.doi.org/10.1128/aem.00790-18.
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ABSTRACTDespite observations of steel corrosion in nitrate-reducing environments, processes of nitrate-dependent microbially influenced corrosion (MIC) remain poorly understood and difficult to identify. We evaluated carbon steel corrosion byShewanella oneidensisMR-1 under nitrate-reducing conditions using a split-chamber/zero-resistance ammetry (ZRA) technique. This approach entails the deployment of two metal (carbon steel 1018 in this case) electrodes into separate chambers of an electrochemical split-chamber unit, where the microbiology or chemistry of the chambers can be manipulated. This approach mimics the conditions of heterogeneous metal coverage that can lead to uniform and pitting corrosion. The current between working electrode 1 (WE1) and WE2 can be used to determine rates, mechanisms, and, we now show, extents of corrosion. WhenS. oneidensiswas incubated in the WE1 chamber with lactate under nitrate-reducing conditions, nitrite transiently accumulated, and electron transfer from WE2 to WE1 occurred as long as nitrite was present. Nitrite in the WE1 chamber (withoutS. oneidensis) induced electron transfer in the same direction, indicating that nitrite cathodically protected WE1 and accelerated the corrosion of WE2. WhenS. oneidensiswas incubated in the WE1 chamber without an electron donor, nitrate reduction proceeded, and electron transfer from WE2 to WE1 also occurred, indicating that the microorganism could use the carbon steel electrode as an electron donor for nitrate reduction. Our results indicate that under nitrate-reducing conditions, uniform and pitting carbon steel corrosion can occur due to nitrite accumulation and the use of steel-Fe(0) as an electron donor, but conditions of sustained nitrite accumulation can lead to more-aggressive corrosive conditions.IMPORTANCEMicrobially influenced corrosion (MIC) causes damage to metals and metal alloys that is estimated to cost over $100 million/year in the United States for prevention, mitigation, and repair. While MIC occurs in a variety of settings and by a variety of organisms, the mechanisms by which microorganisms cause this damage remain unclear. Steel pipe and equipment may be exposed to nitrate, especially in oil and gas production, where this compound is used for corrosion and “souring” control. In this paper, we show uniform and pitting MIC under nitrate-reducing conditions and that a major mechanism by which it occurs is via the heterogeneous cathodic protection of metal surfaces by nitrite as well as by the microbial oxidation of steel-Fe(0).
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Yagi, Jane M., Joseph M. Suflita, Lisa M. Gieg, Christopher M. DeRito, Che-Ok Jeon y Eugene L. Madsen. "Subsurface Cycling of Nitrogen and Anaerobic Aromatic Hydrocarbon Biodegradation Revealed by Nucleic Acid and Metabolic Biomarkers". Applied and Environmental Microbiology 76, n.º 10 (26 de marzo de 2010): 3124–34. http://dx.doi.org/10.1128/aem.00172-10.
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ABSTRACT Microbial processes are crucial for ecosystem maintenance, yet documentation of these processes in complex open field sites is challenging. Here we used a multidisciplinary strategy (site geochemistry, laboratory biodegradation assays, and field extraction of molecular biomarkers) to deduce an ongoing linkage between aromatic hydrocarbon biodegradation and nitrogen cycling in a contaminated subsurface site. Three site wells were monitored over a 10-month period, which revealed fluctuating concentrations of nitrate, ammonia, sulfate, sulfide, methane, and other constituents. Biodegradation assays performed under multiple redox conditions indicated that naphthalene metabolism was favored under aerobic conditions. To explore in situ field processes, we measured metabolites of anaerobic naphthalene metabolism and expressed mRNA transcripts selected to document aerobic and anaerobic microbial transformations of ammonia, nitrate, and methylated aromatic contaminants. Gas chromatography-mass spectrometry detection of two carboxylated naphthalene metabolites and transcribed benzylsuccinate synthase, cytochrome c nitrite reductase, and ammonia monooxygenase genes indicated that anaerobic metabolism of aromatic compounds and both dissimilatory nitrate reduction to ammonia (DNRA) and nitrification occurred in situ. These data link formation (via DNRA) and destruction (via nitrification) of ammonia to in situ cycling of nitrogen in this subsurface habitat, where metabolism of aromatic pollutants has led to accumulation of reduced metabolic end products (e.g., ammonia and methane).
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Lam, P., M. M. Jensen, A. Kock, K. A. Lettmann, Y. Plancherel, G. Lavik, H. W. Bange y M. M. M. Kuypers. "Origin and fate of the secondary nitrite maximum in the Arabian Sea". Biogeosciences Discussions 8, n.º 2 (7 de marzo de 2011): 2357–402. http://dx.doi.org/10.5194/bgd-8-2357-2011.
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Abstract. The Arabian Sea harbours one of the three major oxygen minimum zones (OMZs) in the world's oceans, and it alone is estimated to account for ~10–20% of global oceanic nitrogen (N) loss. While actual rate measurements have been few, the consistently high accumulation of nitrite (NO2−) coinciding with suboxic conditions in the central-northeastern part of the Arabian Sea has led to the general belief that this is the region where active N-loss takes place. Most subsequent field studies on N-loss have thus been drawn almost exclusively to the central-NE. However, a recent study measured only low to undetectable N-loss activities in this region, compared to orders of magnitude higher rates measured towards the Omani shelf where little NO2− accumulated (Jensen et al., 2011). In this paper, we further explore this discrepancy by comparing the NO2− producing and consuming processes, and examining the relationship between the overall NO2− balance and active N-loss in the Arabian Sea. Based on a combination of 15N-incubation experiments, functional gene expression analyses, nutrient profiling and flux modeling, our results showed that NO2− accumulated in the Central-NE Arabian Sea due to a net production via primarily active nitrate (NO3−) reduction and to a certain extent ammonia oxidation. Meanwhile, NO2− consumption via anammox, denitrification and dissimilatory nitrate/nitrite reduction to ammonium (NH4+) were hardly detectable in this region, though some loss to NO2− oxidation was predicted from modeled NO3− changes. No significant correlation was found between NO2− and N-loss rates (p>0.05). This discrepancy between NO2− accumulation and lack of active N-loss in the Central-NE Arabian Sea is best explained by the deficiency of organic matter that is directly needed for further NO2− reduction to N2O, N2 and NH4+, and indirectly for the remineralized NH4+ required by anammox. Altogether, our data do not support the long-held view that NO2− accumulation is a direct activity indicator of N-loss in the Arabian Sea or other OMZs. Instead, NO2− accumulation more likely corresponds to long-term integrated N-loss that has passed the prime of high and/or consistent in situ activities.
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Lam, P., M. M. Jensen, A. Kock, K. A. Lettmann, Y. Plancherel, G. Lavik, H. W. Bange y M. M. M. Kuypers. "Origin and fate of the secondary nitrite maximum in the Arabian Sea". Biogeosciences 8, n.º 6 (20 de junio de 2011): 1565–77. http://dx.doi.org/10.5194/bg-8-1565-2011.
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Abstract. The Arabian Sea harbours one of the three major oxygen minimum zones (OMZs) in the world's oceans, and it alone is estimated to account for ~10–20 % of global oceanic nitrogen (N) loss. While actual rate measurements have been few, the consistently high accumulation of nitrite (NO2−) coinciding with suboxic conditions in the central-northeastern part of the Arabian Sea has led to the general belief that this is the region where active N-loss takes place. Most subsequent field studies on N-loss have thus been drawn almost exclusively to the central-NE. However, a recent study measured only low to undetectable N-loss activities in this region, compared to orders of magnitude higher rates measured towards the Omani Shelf where little NO2− accumulated (Jensen et al., 2011). In this paper, we further explore this discrepancy by comparing the NO2−-producing and consuming processes, and examining the relationship between the overall NO2− balance and active N-loss in the Arabian Sea. Based on a combination of 15N-incubation experiments, functional gene expression analyses, nutrient profiling and flux modeling, our results showed that NO2− accumulated in the central-NE Arabian Sea due to a net production via primarily active nitrate (NO3−) reduction and to a certain extent ammonia oxidation. Meanwhile, NO2− consumption via anammox, denitrification and dissimilatory nitrate/nitrite reduction to ammonium (NH4+) were hardly detectable in this region, though some loss to NO2− oxidation was predicted from modeled NO3− changes. No significant correlation was found between NO2− and N-loss rates (p>0.05). This discrepancy between NO2− accumulation and lack of active N-loss in the central-NE Arabian Sea is best explained by the deficiency of labile organic matter that is directly needed for further NO2− reduction to N2O, N2 and NH4+, and indirectly for the remineralized NH4+ required by anammox. Altogether, our data do not support the long-held view that NO2− accumulation is a direct activity indicator of N-loss in the Arabian Sea or other OMZs. Instead, NO2− accumulation more likely corresponds to long-term integrated N-loss that has passed the prime of high and/or consistent in situ activities.
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Smith, Cindy J., David B. Nedwell, Liang F. Dong y A. Mark Osborn. "Diversity and Abundance of Nitrate Reductase Genes (narG and napA), Nitrite Reductase Genes (nirS and nrfA), and Their Transcripts in Estuarine Sediments". Applied and Environmental Microbiology 73, n.º 11 (30 de marzo de 2007): 3612–22. http://dx.doi.org/10.1128/aem.02894-06.
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ABSTRACT Estuarine systems are the major conduits for the transfer of nitrate from agricultural and other terrestrial-anthropogenic sources into marine ecosystems. Within estuarine sediments some microbially driven processes (denitrification and anammox) result in the net removal of nitrogen from the environment, while others (dissimilatory nitrate reduction to ammonium) do not. In this study, molecular approaches have been used to investigate the diversity, abundance, and activity of the nitrate-reducing communities in sediments from the hypernutrified Colne estuary, United Kingdom, via analysis of nitrate and nitrite reductase genes and transcripts. Sequence analysis of cloned PCR-amplified narG, napA, and nrfA gene sequences showed the indigenous nitrate-reducing communities to be both phylogenetically diverse and also divergent from previously characterized nitrate reduction sequences in soils and offshore marine sediments and from cultured nitrate reducers. In both the narG and nrfA libraries, the majority of clones (48% and 50%, respectively) were related to corresponding sequences from delta-proteobacteria. A suite of quantitative PCR primers and TaqMan probes was then developed to quantify phylotype-specific nitrate (narG and napA) and nitrite reductase (nirS and nrfA) gene and transcript numbers in sediments from three sites along the estuarine nitrate gradient. In general, both nitrate and nitrite reductase gene copy numbers were found to decline significantly (P < 0.05) from the estuary head towards the estuary mouth. The development and application, for the first time, of quantitative reverse transcription-PCR assays to quantify mRNA sequences in sediments revealed that transcript numbers for three of the five phylotypes quantified were greatest at the estuary head.
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Versantvoort, Wouter, Arjan Pol, Mike S. M. Jetten, Laura van Niftrik, Joachim Reimann, Boran Kartal y Huub J. M. Op den Camp. "Multiheme hydroxylamine oxidoreductases produce NO during ammonia oxidation in methanotrophs". Proceedings of the National Academy of Sciences 117, n.º 39 (10 de septiembre de 2020): 24459–63. http://dx.doi.org/10.1073/pnas.2011299117.
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Aerobic and nitrite-dependent methanotrophs make a living from oxidizing methane via methanol to carbon dioxide. In addition, these microorganisms cometabolize ammonia due to its structural similarities to methane. The first step in both of these processes is catalyzed by methane monooxygenase, which converts methane or ammonia into methanol or hydroxylamine, respectively. Methanotrophs use methanol for energy conservation, whereas toxic hydroxylamine is a potent inhibitor that needs to be rapidly removed. It is suggested that many methanotrophs encode a hydroxylamine oxidoreductase (mHAO) in their genome to remove hydroxylamine, although biochemical evidence for this is lacking. HAOs also play a crucial role in the metabolism of aerobic and anaerobic ammonia oxidizers by converting hydroxylamine to nitric oxide (NO). Here, we purified an HAO from the thermophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV and characterized its kinetic properties. This mHAO possesses the characteristic P460 chromophore and is active up to at least 80 °C. It catalyzes the rapid oxidation of hydroxylamine to NO. In methanotrophs, mHAO efficiently removes hydroxylamine, which severely inhibits calcium-dependent, and as we show here, lanthanide-dependent methanol dehydrogenases, which are more prevalent in the environment. Our results indicate that mHAO allows methanotrophs to thrive under high ammonia concentrations in natural and engineered ecosystems, such as those observed in rice paddy fields, landfills, or volcanic mud pots, by preventing the accumulation of inhibitory hydroxylamine. Under oxic conditions, methanotrophs mainly oxidize ammonia to nitrite, whereas in hypoxic and anoxic environments reduction of both ammonia-derived nitrite and NO could lead to nitrous oxide (N2O) production.
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Khaligh, Nader Ghaffari, Mohd Rafie Johan y Juan Joon Ching. "Saccharin: a cheap and mild acidic agent for the synthesis of azo dyes via telescoped dediazotization". Green Processing and Synthesis 8, n.º 1 (28 de enero de 2019): 24–29. http://dx.doi.org/10.1515/gps-2017-0133.
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Abstract Green synthesis methods are considered as a safer alternative to the conventional synthetic processes due to their eco-friendly nature, cost-effectiveness, and easy handling. In the present study, an eco-friendly and sustainable method for the synthesis of stable arenediazonium has been developed using saccharin as a cheap and mild acidic agent and tert-butyl nitrite as a diazotization reagent for the first time. These stable intermediates were used in the azo coupling reaction with 4-hydroxybenzaldehyde via telescoped dediazotization. The current method has advantages such as reduced waste by avoiding solvent for the purification of intermediate in diazotization step, cost-effectiveness, simple experimental procedure, good yield of azo dyes, metal-free waste, and environmentally benign conditions. An interesting aspect of this study is the recovery of saccharin from the reaction, which could be reused.
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Xu, Min Nina, Yanhua Wu, Li Wei Zheng, Zhenzhen Zheng, Huade Zhao, Edward A. Laws y Shuh-Ji Kao. "Quantification of multiple simultaneously occurring nitrogen flows in the euphotic ocean". Biogeosciences 14, n.º 4 (3 de marzo de 2017): 1021–38. http://dx.doi.org/10.5194/bg-14-1021-2017.
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Abstract. The general features of the N cycle in the sunlit region of the ocean are well known, but methodological difficulties have previously confounded simultaneous quantification of transformation rates among the many different forms of N, e.g., ammonium (NH4+), nitrite (NO2−), nitrate (NO3−), and particulate/dissolved organic nitrogen (PN/DON). However, recent advances in analytical methodology have made it possible to employ a convenient isotope labeling technique to quantify in situ fluxes among oft-measured nitrogen species within the euphotic zone. Addition of a single 15N-labeled NH4+ tracer and monitoring of the changes in the concentrations and isotopic compositions of the total dissolved nitrogen (TDN), PN, NH4+, NO2−, and NO3− pools allowed us to quantify the 15N and 14N fluxes simultaneously. Constraints expressing the balance of 15N and 14N fluxes between the different N pools were expressed in the form of simultaneous equations, the unique solution of which via matrix inversion yielded the relevant N fluxes, including rates of NH4+, NO2−, and NO3− uptake; ammonia oxidation; nitrite oxidation; DON release; and NH4+ uptake by bacteria. The matrix inversion methodology that we used was designed specifically to analyze the results of incubations under simulated in situ conditions in the euphotic zone. By taking into consideration simultaneous fluxes among multiple N pools, we minimized potential artifacts caused by non-targeted processes in traditional source–product methods. The proposed isotope matrix method facilitates post hoc analysis of data from on-deck incubation experiments and can be used to probe effects of environmental factors (e.g., pH, temperature, and light) on multiple processes under controlled conditions.
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Zakem, Emily J., Barbara Bayer, Wei Qin, Alyson E. Santoro, Yao Zhang y Naomi M. Levine. "Controls on the relative abundances and rates of nitrifying microorganisms in the ocean". Biogeosciences 19, n.º 23 (2 de diciembre de 2022): 5401–18. http://dx.doi.org/10.5194/bg-19-5401-2022.
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Abstract. Nitrification controls the oxidation state of bioavailable nitrogen. Distinct clades of chemoautotrophic microorganisms – predominantly ammonia-oxidizing archaea (AOA) and nitrite-oxidizing bacteria (NOB) – regulate the two steps of nitrification in the ocean, but explanations for their observed relative abundances and nitrification rates remain incomplete and their contributions to the global marine carbon cycle via carbon fixation remain unresolved. Using a mechanistic microbial ecosystem model with nitrifying functional types, we derive simple expressions for the controls on AOA and NOB in the deep, oxygenated open ocean. The relative biomass yields, loss rates, and cell quotas of AOA and NOB control their relative abundances, though we do not need to invoke a difference in loss rates to explain the observed relative abundances. The supply of ammonium, not the traits of AOA or NOB, controls the relatively equal ammonia and nitrite oxidation rates at steady state. The relative yields of AOA and NOB alone set their relative bulk carbon fixation rates in the water column. The quantitative relationships are consistent with multiple in situ datasets. In a complex global ecosystem model, nitrification emerges dynamically across diverse ocean environments, and ammonia and nitrite oxidation and their associated carbon fixation rates are decoupled due to physical transport and complex ecological interactions in some environments. Nevertheless, the simple expressions capture global patterns to first order. The model provides a mechanistic upper estimate on global chemoautotrophic carbon fixation of 0.2–0.5 Pg C yr−1, which is on the low end of the wide range of previous estimates. Modeled carbon fixation by AOA (0.2–0.3 Pg C yr−1) exceeds that of NOB (about 0.1 Pg C yr−1) because of the higher biomass yield of AOA. The simple expressions derived here can be used to quantify the biogeochemical impacts of additional metabolic pathways (i.e., mixotrophy) of nitrifying clades and to identify alternative metabolisms fueling carbon fixation in the deep ocean.
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Bonacci, Gustavo, Francisco J. Schopfer, Carlos I. Batthyany, Tanja K. Rudolph, Volker Rudolph, Nicholas K. H. Khoo, Eric E. Kelley y Bruce A. Freeman. "Electrophilic Fatty Acids Regulate Matrix Metalloproteinase Activity and Expression". Journal of Biological Chemistry 286, n.º 18 (15 de marzo de 2011): 16074–81. http://dx.doi.org/10.1074/jbc.m111.225029.
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Nitro-fatty acids (NO2-FA) are electrophilic signaling mediators formed by reactions of nitric oxide and nitrite. NO2-FA exert anti-inflammatory signaling actions through post-translational protein modifications. We report that nitro-oleic acid (OA-NO2) stimulates proMMP-7 and proMMP-9 proteolytic activity via adduction of the conserved cysteine switch domain thiolate. Biotin-labeled OA-NO2 showed this adduction occurs preferentially with latent forms of MMP, confirming a role for thiol alkylation by OA-NO2 in MMP activation. In addition to regulating pro-MMP activation, MMP expression was modulated by OA-NO2 via activation of peroxisome proliferator-activated receptor-γ. MMP-9 transcription was decreased in phorbol 12-myristate 13-acetate-stimulated THP-1 macrophages to an extent similar to that induced by the peroxisome proliferator-activated receptor-γ agonist Rosiglitazone. This was affirmed using a murine model of atherosclerosis, ApoE−/− mice, where in vivo OA-NO2 administration suppressed MMP expression in atherosclerotic lesions. These findings reveal that electrophilic fatty acid derivatives can serve as effectors during inflammation, first by activating pro-MMP proteolytic activity via alkylation of the cysteine switch domain, and then by transcriptionally inhibiting MMP expression, thereby limiting the further progression of inflammatory processes.
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Borrero-de Acuña, José Manuel, Manfred Rohde, Josef Wissing, Lothar Jänsch, Max Schobert, Gabriella Molinari, Kenneth N. Timmis, Martina Jahn y Dieter Jahn. "Protein Network of the Pseudomonas aeruginosa Denitrification Apparatus". Journal of Bacteriology 198, n.º 9 (22 de febrero de 2016): 1401–13. http://dx.doi.org/10.1128/jb.00055-16.
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ABSTRACTOxidative phosphorylation using multiple-component, membrane-associated protein complexes is the most effective way for a cell to generate energy. Here, we systematically investigated the multiple protein-protein interactions of the denitrification apparatus of the pathogenic bacteriumPseudomonas aeruginosa. During denitrification, nitrate (Nar), nitrite (Nir), nitric oxide (Nor), and nitrous oxide (Nos) reductases catalyze the reaction cascade of NO3−→ NO2−→ NO → N2O → N2. Genetic experiments suggested that the nitric oxide reductase NorBC and the regulatory protein NosR are the nucleus of the denitrification protein network. We utilized membrane interactomics in combination with electron microscopy colocalization studies to elucidate the corresponding protein-protein interactions. The integral membrane proteins NorC, NorB, and NosR form the core assembly platform that binds the nitrate reductase NarGHI and the periplasmic nitrite reductase NirS via its maturation factor NirF. The periplasmic nitrous oxide reductase NosZ is linked via NosR. The nitrate transporter NarK2, the nitrate regulatory system NarXL, various nitrite reductase maturation proteins, NirEJMNQ, and the Nos assembly lipoproteins NosFL were also found to be attached. A number of proteins associated with energy generation, including electron-donating dehydrogenases, the complete ATP synthase, almost all enzymes of the tricarboxylic acid (TCA) cycle, and the Sec system of protein transport, among many other proteins, were found to interact with the denitrification proteins. This deduced nitrate respirasome is presumably only one part of an extensive cytoplasmic membrane-anchored protein network connecting cytoplasmic, inner membrane, and periplasmic proteins to mediate key activities occurring at the barrier/interface between the cytoplasm and the external environment.IMPORTANCEThe processes of cellular energy generation are catalyzed by large multiprotein enzyme complexes. The molecular basis for the interaction of these complexes is poorly understood. We employed membrane interactomics and electron microscopy to determine the protein-protein interactions involved. The well-investigated enzyme complexes of denitrification of the pathogenic bacteriumPseudomonas aeruginosaserved as a model. Denitrification is one essential step of the universal N cycle and provides the bacterium with an effective alternative to oxygen respiration. This process allows the bacterium to form biofilms, which create low-oxygen habitats and which are a key in the infection mechanism. Our results provide new insights into the molecular basis of respiration, as well as opening a new window into the infection strategies of this pathogen.
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Shen, Li-dong, Shuai Liu, Qian Huang, Xu Lian, Zhan-fei He, Sha Geng, Ren-cun Jin et al. "Evidence for the Cooccurrence of Nitrite-Dependent Anaerobic Ammonium and Methane Oxidation Processes in a Flooded Paddy Field". Applied and Environmental Microbiology 80, n.º 24 (26 de septiembre de 2014): 7611–19. http://dx.doi.org/10.1128/aem.02379-14.
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ABSTRACTAnaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) are two of the most recent discoveries in the microbial nitrogen cycle. In the present study, we provide direct evidence for the cooccurrence of the anammox and n-damo processes in a flooded paddy field in southeastern China. Stable isotope experiments showed that the potential anammox rates ranged from 5.6 to 22.7 nmol N2g−1(dry weight) day−1and the potential n-damo rates varied from 0.2 to 2.1 nmol CO2g−1(dry weight) day−1in different layers of soil cores. Quantitative PCR showed that the abundance of anammox bacteria ranged from 1.0 × 105to 2.0 × 106copies g−1(dry weight) in different layers of soil cores and the abundance of n-damo bacteria varied from 3.8 × 105to 6.1 × 106copies g−1(dry weight). Phylogenetic analyses of the recovered 16S rRNA gene sequences showed that anammox bacteria affiliated with “CandidatusBrocadia” and “CandidatusKuenenia” and n-damo bacteria related to “CandidatusMethylomirabilis oxyfera” were present in the soil cores. It is estimated that a total loss of 50.7 g N m−2per year could be linked to the anammox process, which is at intermediate levels for the nitrogen flux ranges of aerobic ammonium oxidation and denitrification reported in wetland soils. In addition, it is estimated that a total of 0.14 g CH4m−2per year could be oxidized via the n-damo process, while this rate is at the lower end of the aerobic methane oxidation rates reported in wetland soils.
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Teillout, Anne-Lucie, Pedro de Oliveira, Jérôme Marrot, Robertha Howell, Neus Vilà, Alain Walcarius y Israël Mbomekallé. "Synthesis, Crystal Structure, Electrochemistry and Electro-Catalytic Properties of the Manganese-Containing Polyoxotungstate, [(Mn(H2O)3)2(H2W12O42)]6−". Inorganics 7, n.º 2 (2 de febrero de 2019): 15. http://dx.doi.org/10.3390/inorganics7020015.
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We present the synthesis and structural characterization of the manganese-containing polyoxotungstate, [(Mn(H2O)3)2(H2W12O42)]6− (1), obtained by reaction of MnCl2 with six equivalents of Na2WO4 in the presence of Zn(CH3COO)2 in acetate medium (pH 4.7). This has been assessed by various techniques (FTIR, TGA, UV-Visible, XPS, elemental analysis, single crystal X-ray and electrochemistry). Single-crystal X-ray analyses showed that, in the solid state, 1 forms a 2-D network in which [H2W12O42]10− fragments are linked in pairs via Mn2+ ions, leading to linear chains of the form [(Mn(H2O)3)2(H2W12O42)]n6n−. The connection between chains occurs also via Mn2+ ions which bind [H2W12O42]10− fragments belonging to two adjacent chains, forming an infinite 2-D network. A complete electrochemical study was done in aqueous solution where 1 is stable in the pH range 1 to 6. This complex undergoes multiple electron-transfer processes that lead to the electro-generation of manganese high oxidation state species that catalyse water electro-oxidation. 1 is also effective in the electro-catalytic reduction of nitrite and dioxygen.
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Lyons, W. Berry, A. Paul Mayewski, Lonnie G. Thompson y Boyd Allen. "The Glaciochemistry of Snow-Pits from Quelccaya Ice Cap, Peru, 1982". Annals of Glaciology 7 (1985): 84–88. http://dx.doi.org/10.3189/s0260305500005954.
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We present glaciochemical data from a pilot study of two snow-pits from Quelccaya ice cap, Peruvian Andes. These are the first samples to be analyzed from Quelccaya for nitrate and sulfate by ion chromatography (IC), for nitrate-plus-nitrite, reactive silicate and reactive iron by colorimetry, and for sodium by atomic absorption spectrophotometry. The 3 m pits used in this study represent a one year record of mass accumulation and the 29 samples collected provide the first glaciochemical data from this area which can be compared with glaciochemical studies from other locations.Reactive iron, reactive silicate and sodium, and the profiles of >0.63μm microparticles from Thompson and others (1984) are coincident, suggesting that transport and deposition into this area of each species are controlled by similar processes. The common source is probably local, resulting from crustal weathering. In general, the reactive silicate values are lower than those observed in other alpine glacier ice. The highest sulfate and nitrate values were observed in the upper few centimeters of the snow-pit. Most of the sulfate concentrations were less than 3 μM and are similar to values obtained for fresh surface snows from Bolivia (Stallard and Edmond 1981). Since biological gaseous emissions are thought to be the major source of sulfur and nitrogen to the atmosphere over the Amazon basin, the sulfate and nitrate fluctuations may be due to seasonal biological input and/or seasonal shifts in wind direction bringing material to Quelccaya.With only one exception, the colorimetric nitrate-plus-nitrite data were higher than the IC nitrate data. Unfortunately, the IC analyses were conducted 81 d after the colorimetric analyses. The difference between the two data sets could be attributable to the following: (1) the colorimetric technique may yield erroneously high results as suggested for polar ice by Herron (1982), (2) the IC technique yields erroneously low results due, in part, to the possible exclusion of nitrite concentrations, and/or (3) nitrite was lost via biological removal during the 81 d period before the IC analyses. If the IC data are correct, the mean nitrate value is 0.4μΜ (n = 29). This value is similar to those reported from pre-industrial aged polar ice (Herron 1982). If the colorimetric mean value (1.1 μM) is correct, it is similar to colorimetrically determined values from other high-elevation alpine ice (Lyons and Mayewski 1983).
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Lyons, W. Berry, A. Paul Mayewski, Lonnie G. Thompson y Boyd Allen. "The Glaciochemistry of Snow-Pits from Quelccaya Ice Cap, Peru, 1982". Annals of Glaciology 7 (1985): 84–88. http://dx.doi.org/10.1017/s0260305500005954.
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We present glaciochemical data from a pilot study of two snow-pits from Quelccaya ice cap, Peruvian Andes. These are the first samples to be analyzed from Quelccaya for nitrate and sulfate by ion chromatography (IC), for nitrate-plus-nitrite, reactive silicate and reactive iron by colorimetry, and for sodium by atomic absorption spectrophotometry. The 3 m pits used in this study represent a one year record of mass accumulation and the 29 samples collected provide the first glaciochemical data from this area which can be compared with glaciochemical studies from other locations. Reactive iron, reactive silicate and sodium, and the profiles of >0.63μm microparticles from Thompson and others (1984) are coincident, suggesting that transport and deposition into this area of each species are controlled by similar processes. The common source is probably local, resulting from crustal weathering. In general, the reactive silicate values are lower than those observed in other alpine glacier ice. The highest sulfate and nitrate values were observed in the upper few centimeters of the snow-pit. Most of the sulfate concentrations were less than 3 μM and are similar to values obtained for fresh surface snows from Bolivia (Stallard and Edmond 1981). Since biological gaseous emissions are thought to be the major source of sulfur and nitrogen to the atmosphere over the Amazon basin, the sulfate and nitrate fluctuations may be due to seasonal biological input and/or seasonal shifts in wind direction bringing material to Quelccaya. With only one exception, the colorimetric nitrate-plus-nitrite data were higher than the IC nitrate data. Unfortunately, the IC analyses were conducted 81 d after the colorimetric analyses. The difference between the two data sets could be attributable to the following: (1) the colorimetric technique may yield erroneously high results as suggested for polar ice by Herron (1982), (2) the IC technique yields erroneously low results due, in part, to the possible exclusion of nitrite concentrations, and/or (3) nitrite was lost via biological removal during the 81 d period before the IC analyses. If the IC data are correct, the mean nitrate value is 0.4μΜ (n = 29). This value is similar to those reported from pre-industrial aged polar ice (Herron 1982). If the colorimetric mean value (1.1 μM) is correct, it is similar to colorimetrically determined values from other high-elevation alpine ice (Lyons and Mayewski 1983).
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Chen, Jinghua, Lulu Liu, Weiwei Wang y Haichun Gao. "Nitric Oxide, Nitric Oxide Formers and Their Physiological Impacts in Bacteria". International Journal of Molecular Sciences 23, n.º 18 (15 de septiembre de 2022): 10778. http://dx.doi.org/10.3390/ijms231810778.
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Nitric oxide (NO) is an active and critical nitrogen oxide in the microbe-driven nitrogen biogeochemical cycle, and is of great interest to medicine and the biological sciences. As a gas molecule prior to oxygen, NO respiration represents an early form of energy generation via various reactions in prokaryotes. Major enzymes for endogenous NO formation known to date include two types of nitrite reductases in denitrification, hydroxylamine oxidoreductase in ammonia oxidation, and NO synthases (NOSs). While the former two play critical roles in shaping electron transport pathways in bacteria, NOSs are intracellular enzymes catalyzing metabolism of certain amino acids and have been extensively studied in mammals. NO interacts with numerous cellular targets, most of which are redox-active proteins. Doing so, NO plays harmful and beneficial roles by affecting diverse biological processes within bacterial physiology. Here, we discuss recent advances in the field, including NO-forming enzymes, the molecular mechanisms by which these enzymes function, physiological roles of bacterial NOSs, and regulation of NO homeostasis in bacteria.
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Sivalingam, Vasan, Carlos Dinamarca, Eshetu Janka, Sergey Kukankov, Shuai Wang y Rune Bakke. "Effect of Intermittent Aeration in a Hybrid Vertical Anaerobic Biofilm Reactor (HyVAB) for Reject Water Treatment". Water 12, n.º 4 (17 de abril de 2020): 1151. http://dx.doi.org/10.3390/w12041151.
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Water from anaerobic sludge dewatering (reject water that is recycled to the inlet main process treatment) from the Knarrdalstrand municipal wastewater treatment plant in Porsgrunn, Norway, contains 2.4 g/L of total chemical oxygen demand (TCOD) and 550 mg/L NH4-N (annual average). The high concentration of ammonium causes disturbances in the mainstream physical and chemical processes, while only a small fraction of the organics is biodegradable. A pilot-scale hybrid vertical anaerobic biofilm (HyVAB) reactor combining anaerobic and aerobic treatment was tested for reject water treatment to reduce process disturbances. The pilot HyVAB was prepared for the study with continuous aeration of the aerobic part of the reactor for 200 days, while two intermittent aeration schemes were applied during the three-month test period. Ammonium removal efficiency increased from 8% during the continuous aeration period to 50% at the end of the test when a short (7 min) aeration cycle was applied. COD removal was close to 20%, which was mainly obtained in the anaerobic stage and not significantly influenced by the aerations schemes. Simultaneous partial nitrification and denitrification were established in the biofilm that alternated between aerobic and anoxic conditions. The observed high ammonium removal is explained by two alternative shortcut processes via nitrite. The lack of biodegradable organics in the aerated stage suggests that most of the nitrogen removal was via the anammox pathway (autotrophic denitrification). The HyVAB, combining an anaerobic sludge bed and an intermittently aerated biofilm, appears to be an efficient process to treat high ammonium containing reject water.
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Vujadinovic, Dragan, Bojan Golic, Vladimir Tomovic, Vesna Gojkovic, Milan Vukic y Radoslav Grujic. "Antimicrobial activity of essential oils and fruits supplement in reduced nitrite salts condition". Zbornik Matice srpske za prirodne nauke, n.º 133 (2017): 251–60. http://dx.doi.org/10.2298/zmspn1733251v.
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Because of the growing negative perception of consumers related to the use of meat products produced by conventional curing methods, organic and natural products are increasingly accepted by consumers. Such products contain a large number of natural products derived from plants, spices, as well as their derivatives in form of essential oils, extracts, concentrates, and so on. These derivatives contain large number of active substances which are known to inhibit the metabolic processes of bacteria, yeasts and molds. Therefore, the goal of this paper was to investigate the synergistic antimicrobial activity of the models with a reduced presence of nitrite salt in aqueous solution, emulsions of essential oils in varying concentrations in vivo via antibiogram tests on pathogenic microorganisms. The effect of the six model groups was analyzed. Two groups were fruit powder solutions in concentrations of 0.2% to 1.2% (Acerola powder and fruit powder mix), while the other four groups were models of aqueous emulsion of essential oil in concentrations ranging from 0.05% to 1.2% (tea tree, clove, oregano, and cinnamon essential oils). In all models reduced amount of the sodium salt of 1.80%, 0.0075% nitrite salt and the liquid derivative as a natural source of the nitrate salt of 3% were used. Antibiogram tests were performed on five pathogenic bacteria (C. perfringens, E. coli, S. enterica, L. monocytogenes, and S. aureus). All antibiogram tests were performed according to Kirby-Bauer disk diffusion protocol. Results of antibiograms showed that without the presence of additional antimicrobial agents, in model systems with reduced content of salts, inhibition zones were not detected. Additionally, models with essential oils of tea tree oil and oregano had the widest inhibition zone diameters, ranging from 17.76?0.48mm for E. coli up to 42.50?0.13mm for S. aureus.
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da Silva, Layzon A. Lemos, Louis P. Sandjo, Laura S. Assunção, Anne N. Prigol, Carolina D. de Siqueira, Tânia B. Creczynski-Pasa, Marcus T. Scotti, Luciana Scotti, Fabíola B. Filippin-Monteiro y Maique W. Biavatti. "Semisynthetic Sesquiterpene Lactones Generated by the Sensibility of Glaucolide B to Lewis and Brønsted–Lowry Acids and Bases: Cytotoxicity and Anti-Inflammatory Activities". Molecules 28, n.º 3 (27 de enero de 2023): 1243. http://dx.doi.org/10.3390/molecules28031243.
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Sesquiterpene lactone (SL) subtypes including hirsutinolide and cadinanolide have a controversial genesis. Metabolites of these classes are either described as natural products or as artifacts produced via the influence of solvents, chromatographic mobile phases, and adsorbents used in phytochemical studies. Based on this divergence, and to better understand the sensibility of these metabolites, different pH conditions were used to prepare semisynthetic SLs and evaluate the anti-inflammatory and antiproliferative activities. Therefore, glaucolide B (1) was treated with various Brønsted–Lowry and Lewis acids and bases—the same approach was applied to some of its derivatives—allowing us to obtain 14 semisynthetic SL derivatives, 10 of which are hereby reported for the first time. Hirsutinolide derivatives 7a (CC50 = 5.0 µM; SI = 2.5) and 7b (CC50 = 11.2 µM; SI = 2.5) and the germacranolide derivative 8a (CC50 = 3.1 µM; SI = 3.0) revealed significant cytotoxic activity and selectivity against human melanoma SK-MEL-28 cells when compared with that against non-tumoral HUVEC cells. Additionally, compounds 7a and 7c.1 showed strongly reduced interleukin-6 (IL-6) and nitrite (NOx) release in pre-treated M1 macrophages J774A.1 when stimulated with lipopolysaccharide. Despite the fact that hirsutinolide and cadinanolide SLs may be produced via plant metabolism, this study shows that acidic and alkaline extraction and solid-phase purification processes can promote their formation.
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Cameron, Dale R., Alison M. P. Borrajo, Gregory R. J. Thatcher y Brian M. Bennett. "Organic nitrates, thionitrates, peroxynitrites, and nitric oxide: a molecular orbital study of the (X = O, S) rearrangement, a reaction of potential biological significance". Canadian Journal of Chemistry 73, n.º 10 (1 de octubre de 1995): 1627–38. http://dx.doi.org/10.1139/v95-202.
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The rearrangement of organic thionitrate to sulfenyl nitrite potentially mediates the release of nitric oxide from organic nitrates, such as nitroglycerin, in the presence of thiol. The biological activity of these nitrovasodilators is proposed to result from release of nitric oxide in vivo. The thionitrate rearrangement bears analogy to the rearrangement of peroxynitrous acid to nitric acid, which has been proposed to mediate the biological toxicity of nitric oxide and superoxide. In this paper, the two concerted rearrangement processes and competing homolytic reactions are explored using molecular orbital calculations at levels up to MP4SDQ/6-31G*//MP2/6-31G*. Examination of structure and energy for all conformers and isomers of RSONO2 (R = H, Me), models for organic thionitrates and their isomers, demonstrates that structures corresponding to thionitrates and sulfenyl nitrates are of similar energy. Free energies of reaction for homolysis of these compounds are low (ΔG0 < 19 kcal/mol), whereas the barrier for concerted rearrangement is large (ΔG≠(aq.) = 56 kcal/mol). The larger barrier for concerted rearrangement of peroxynitrous acid to nitric acid (ΔG≠(aq.) = 60 kcal/mol) again compares unfavourably with homolysis (ΔG0 < 11 kcal/mol for homolysis to NO2 or •NO). The transition state structures, confirmed by normal mode and intrinsic reaction coordinate analysis, indicate that considerable structural reorganization is required for concerted rearrangement of the ground state species. These results suggest that concerted rearrangement is not likely to be a viable step in either biological process. However, rearrangement via homolysis and radical recombination may provide an energetically accessible pathway for peroxynitrous acid rearrangement to nitric acid and rearrangement of thionitrate to sulfenyl nitrite. In this case, NO2 will be a primary product of both reactions. Keywords: thionitrate, nitric oxide, peroxynitrite, nitrovasodilator, nitrate.
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Clemitshaw, Kevin C. "Coupling between the Tropospheric Photochemistry of Nitrous Acid (HONO) and Nitric Acid (HNO3)". Environmental Chemistry 3, n.º 1 (2006): 31. http://dx.doi.org/10.1071/en05073.
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Environmental Context.Nitrous acid (HONO) is formed in the troposphere in urban, rural and remote environments via several uncertain heterogeneous and photochemical processes that involve nitric acid (HNO3). A recently recognised process is initiated by the deposition and migration of HNO3 within snow-pack surfaces to form nitrate anions (NO3−). Photo-reduction of NO3− followed by acidification of the nitrite (NO2−) photo-product leads to emissions of gas-phase HONO. Seasonal observations at Halley, Antarctica are consistent with the formation of HONO via this process, which is potentially of global significance because much of the Earth’s land (and sea) surface is covered with snow and is sunlit for much of the year. Both HONO and HNO3 significantly influence the production of ozone (O3), which acts as a greenhouse gas in the troposphere, via their respective roles as a source of hydroxyl radicals (OH•) and as a sink for OH• and nitrogen dioxide (NO2). Abstract.The tropospheric photochemistry of nitrous acid (HONO) and its coupling with that of nitric acid (HNO3) in urban, rural and remote atmospheres are highlighted in terms of established and uncertain homogeneous and heterogeneous sources and sinks, together with known and potential effects and impacts. Observations made at Halley, Antarctica, via optical detection of an azo dye derivative of HONO are consistent with snow-pack photochemical production of HONO, which has potential significance for the production of hydroxyl radicals (OH•) and ozone (O3) on regional and global scales. Recent developments in measurement methods for HONO and HNO3 are also highlighted. It is now timely to conduct a formal intercomparison of the methods in order to evaluate and enhance their capabilities, and to validate the growing body of HONO and HNO3 data obtained in urban, rural and remote locations.
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Borrero-de Acuña, José Manuel, Gabriella Molinari, Manfred Rohde, Thorben Dammeyer, Josef Wissing, Lothar Jänsch, Sagrario Arias et al. "A Periplasmic Complex of the Nitrite Reductase NirS, the Chaperone DnaK, and the Flagellum Protein FliC Is Essential for Flagellum Assembly and Motility in Pseudomonas aeruginosa". Journal of Bacteriology 197, n.º 19 (13 de julio de 2015): 3066–75. http://dx.doi.org/10.1128/jb.00415-15.
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ABSTRACTPseudomonas aeruginosais a ubiquitously occurring environmental bacterium and opportunistic pathogen responsible for various acute and chronic infections. Obviously, anaerobic energy generation via denitrification contributes to its ecological success. To investigate the structural basis for the interconnection of the denitrification machinery to other essential cellular processes, we have sought to identify the protein interaction partners of the denitrification enzyme nitrite reductase NirS in the periplasm. We employed NirS as an affinity-purifiable bait to identify interacting proteinsinvivo. Results obtained revealed that both the flagellar structural protein FliC and the protein chaperone DnaK form a complex with NirS in the periplasm. The interacting domains of NirS and FliC were tentatively identified. The NirS-interacting stretch of amino acids lies within its cytochromecdomain. Motility assays and ultrastructure analyses revealed that anirSmutant was defective in the formation of flagella and correspondingly in swimming motility. In contrast, thefliCmutant revealed an intact denitrification pathway. However, deletion of thenirFgene, coding for a hemed1biosynthetic enzyme, which leads to catalytically inactive NirS, did not abolish swimming ability. This pointed to a structural function for the NirS protein. FliC and NirS were found colocalized with DnaK at the cell surface ofP. aeruginosa. A function of the detected periplasmic NirS-DnaK-FliC complex in flagellum formation and motility was concluded and discussed.IMPORTANCEPhysiological functions in Gram-negative bacteria are connected with the cellular compartment of the periplasm and its membranes. Central enzymatic steps of anaerobic energy generation and the motility mediated by flagellar activity use these cellular structures in addition to multiple other processes. Almost nothing is known about the protein network functionally connecting these processes in the periplasm. Here, we demonstrate the existence of a ternary complex consisting of the denitrifying enzyme NirS, the chaperone DnaK, and the flagellar protein FliC in the periplasm of the pathogenic bacteriumP. aeruginosa. The dependence of flagellum formation and motility on the presence of an intact NirS was shown, structurally connecting both cellular processes, which are important for biofilm formation and pathogenicity of the bacterium.