RESUMEN
In this study we employ computational methods to investigate the influence of aeration strategies on simultaneous nitrification-denitrification processes. Specifically, we explore the impact of periodic and intermittent aeration on denitrification rates, which typically lag behind nitrification rates under identical environmental conditions. A two-dimensional deterministic multi-scale model is employed to elucidate the fundamental processes governing the behavior of membrane aerated biofilm reactors (MABRs). We aim to identify key factors that promote denitrification under varying aeration strategies. Our findings indicate that the concentration of oxygen during the off phase and the duration of the off interval play crucial roles in controlling denitrification. Complete discontinuation of oxygen is not advisable, as it inhibits the formation of anaerobic heterotrophic bacteria, thereby impeding denitrification. Extending the length of the off interval, however, enhances denitrification. Furthermore, we demonstrate that the initial inoculation of the substratum (membrane in this study) influences substrate degradation under periodic aeration, with implications for both nitrification and denitrification. Comparison between continuous and periodic/intermittent aeration scenarios reveals that the latter can extend the operational cycle of MABRs. This extension is attributed to relatively low biofilm growth rates associated with non-continuous aeration strategies. Consequently, our study provides a comprehensive understanding of the intricate interplay between aeration strategies and simultaneous nitrification-denitrification in MABRs. The insights presented herein can contribute significantly to the optimization of MABR performance in wastewater treatment applications.
Asunto(s)
Biopelículas , Reactores Biológicos , Simulación por Computador , Desnitrificación , Conceptos Matemáticos , Membranas Artificiales , Modelos Biológicos , Nitrificación , Oxígeno , Desnitrificación/fisiología , Reactores Biológicos/microbiología , Biopelículas/crecimiento & desarrollo , Oxígeno/metabolismo , Eliminación de Residuos Líquidos/métodos , Aguas Residuales/microbiologíaRESUMEN
Denitrifying anaerobic methane oxidizing (DAMO) archaea plays a significant role in simultaneously nitrogen removal and methane mitigation, yet its limited metabolic activity hinders engineering applications. This study employed biochar to explore its potential for enhancing the metabolic activity and nitrate reduction capacity of DAMO microorganisms. Sawdust biochar (7 g/L) was found to increase the nitrate reduction rate by 2.85 times, although it did not affect the nitrite reduction rate individually. Scanning electron microscopy (SEM) and fluorescence excitation-emission matrix (EEM) analyses revealed that biochar promoted microbial aggregation, and stimulated the secretion of extracellular polymeric substances (EPS). Moreover, biochar bolstered the redox capacity and conductivity of the biofilm, notably enhancing the activity of the electron transfer system by 1.65 times. Key genes involved in intracellular electron transport (Hdr, MHC, Rnf) and membrane transport proteins (BBP, ABC, NDH) of archaea were significantly up-regulated. These findings suggest that biochar regulates electrons generated by reverse methanogenesis to the membrane for nitrate reduction.
Asunto(s)
Archaea , Carbón Orgánico , Desnitrificación , Metano , Nitratos , Oxidación-Reducción , Metano/metabolismo , Archaea/metabolismo , Carbón Orgánico/metabolismo , Nitratos/metabolismo , Transporte de Electrón , Anaerobiosis , Desnitrificación/fisiología , Biopelículas , Matriz Extracelular de Sustancias Poliméricas/metabolismoRESUMEN
This study effectively coupled anammox and mixotrophic denitrification at a high nitrogen load rate of 6.84 g N/L/d with 40 mg/L Fe(II). Fe(II) enhanced the activity of nitrate reductase, nitrite reductase, and hydrazine dehydrogenase enzymes, facilitating accelerated ATP synthesis. Through electrochemical experiments, interspecies electron transfer processes in coupled system were explored. Fe(II) promoted flavin mononucleotide secretion, enhancing electron-donating and electron-accepting capacity by 2.8 and 1.3 times, respectively. Fe(II) triggered the enrichment of autotrophic denitrifying bacteria (Azospira and Hydrogenophaga), transitioning from single organic nutrient to mixotrophic denitrification. Meanwhile, Fe(II) increased Candidatus_Kuenenia abundance from 35.2 % to 49.0 %, establishing the competitive advantage of anammox bacteria over completed denitrifying bacteria (Comamonas). The synergistic interactions between anammox and various denitrification pathways achieved a nitrogen removal rate of 5.88 g N/L/d, with anammox contribution rate of 88.3 %. This study provides insights into broadening the application of partial denitrification /anammox and electron transfer in multi-bacterial coupling systems.
Asunto(s)
Desnitrificación , Oxidación-Reducción , Desnitrificación/fisiología , Transporte de Electrón , Bacterias/metabolismo , Nitrógeno/metabolismo , Interacciones Microbianas , Reactores Biológicos/microbiología , Anaerobiosis , Compuestos Ferrosos/metabolismoRESUMEN
In this study, the possibility of an auto-aggregating bacterium Pseudomonas strain XL-2 with heterotrophic nitrification-aerobic denitrification capacity for improving granulation and nitrogen removal was evaluated. The results showed that the supplementation of strain XL-2 promoted granulation, making R1 (experimental group with strain XL-2) dominated by granules at 14 d, which was 12 days earlier than R2 (control group without strain XL-2). This was attributed to the promotion of extracellular polymeric substances (EPS) secretion, particularly proteins by adding strain XL-2, thereby improving the hydrophobicity of sludge and altering the proteins secondary structures to facilitate aggregation. Meanwhile, adding strain XL-2 improved simultaneous nitrification and denitrification efficiency of R1. Microbial community analysis indicated that strain XL-2 successfully proliferated in aerobic granule sludge and might induce the enrichment of genera such as Flavobacterium and Paracoccus that were favorable for EPS secretion and denitrification, jointly promoting granulation and enhancing nitrogen removal efficiency.
Asunto(s)
Desnitrificación , Nitrificación , Nitrógeno , Pseudomonas stutzeri , Aguas del Alcantarillado , Desnitrificación/fisiología , Nitrificación/fisiología , Pseudomonas stutzeri/metabolismo , Aerobiosis , Aguas del Alcantarillado/microbiología , Procesos Heterotróficos/fisiología , Matriz Extracelular de Sustancias Poliméricas/metabolismo , Reactores BiológicosRESUMEN
Methane-dependent denitrification links the global nitrogen and methane cycles. Since its initial discovery in 2006, this process has been understood to involve a division of labor between an archaeal group and a bacterial group, which sequentially perform nitrate and nitrite reduction, respectively. Yao et al. have now revised this paradigm by identifying a Methylomirabilis bacterium capable of performing methane-dependent complete denitrification on its own.
Asunto(s)
Archaea , Bacterias , Desnitrificación , Metano , Nitratos , Nitritos , Metano/metabolismo , Desnitrificación/fisiología , Nitratos/metabolismo , Nitritos/metabolismo , Bacterias/metabolismo , Archaea/metabolismo , Oxidación-Reducción , Nitrógeno/metabolismoRESUMEN
In order to solve nitrogen pollution in environmental water, two heterotrophic nitrifying and aerobic denitrifying strains isolated from acid paddy soil were identified as Achromobacter sp. strain HNDS-1 and Enterobacter sp. strain HNDS-6 respectively. Strain HNDS-1 and strain HNDS-6 exhibited amazing ability to nitrogen removal. When (NH4)2SO4, KNO3, NaNO2 were used as nitrogen resource respectively, the NH4+-N, NO3--N, NO2--N removal efficiencies of strain HNDS-1 were 93.31%, 89.47%, and 100% respectively, while those of strain HNDS-6 were 82.39%, 96.92%, and 100%. And both of them could remove mixed nitrogen effectively in low C/N (C/Nâ¯=â¯5). Strain HNDS-1 could remove 76.86% NH4+-N and 75.13% NO3--N. And strain HNDS-6 can remove 65.07% NH4+-N and 78.21% NO3--N. A putative ammonia monooxygenase, nitrite reductase, nitrate reductase, assimilatory nitrate reductase, nitrate/nitrite transport protein and nitric oxide reductase of strain HNDS-1, while hydroxylamine reductase, nitrite reductase, nitrate reductase, assimilatory nitrate reductase, nitrate/nitrite transport protein, and nitric oxide reductase of strain HNDS-6 were identified by genomic analysis. DNA-SIP analysis showed that genes Nxr, narG, nirK, norB, nosZ were involved in nitrogen removal pathway, which indicates that the denitrification pathway of strain HNDS-1 and strain HNDS-6 was NO3-âNO2-âNOâN2OâN2 during NH4+-N removal process. And the nitrification pathway of strain HNDS-1 and strain HNDS-6 was NO2-âNO3-, but the nitrification pathway of NH4+â NO2- needs further studies.
Asunto(s)
Achromobacter , Desnitrificación , Enterobacter , Nitrificación , Achromobacter/genética , Achromobacter/metabolismo , Aerobiosis/genética , Aerobiosis/fisiología , Desnitrificación/genética , Desnitrificación/fisiología , Enterobacter/genética , Enterobacter/metabolismo , Nitratos/metabolismo , Nitrificación/genética , Nitrificación/fisiología , Nitrito Reductasas/metabolismo , Nitritos/metabolismo , Nitrógeno/metabolismo , Dióxido de Nitrógeno/metabolismoRESUMEN
Denitrification, a typical biological process mediated by complex environmental factors, i.e., carbon sources and dissolved oxygen (DO), has attracted great attention due to its contribution to the control of eutrophication and the biochemical cycling of nitrogen. However, the effects of carbon source on electron distribution and enzyme expression for enhanced denitrification under competition of electron acceptors (DO and nitrate) remain unclear. Here, we profile the carbon metabolic pathway of polyhydroxybutyrate (PHB) and glucose (Glu) at high and low DO levels (50% and 10% saturated DO, respectively). It was found that PHB enhanced the growth of Pseudomonas stutzeri (model denitrifying bacterium) and improved the specific nitrogen removal rate (SNRR) at all DO levels. The functional proteins had a better affinity for the cofactor nicotinamide-adenine dinucleotide (NADH) than for nicotinamide adenine dinucleotide phosphate (NADPH); thus, more electrons were involved in nitrogen reduction and intracellular PHB production in the PHB groups than in the Glu groups. Furthermore, the expression difference of enzymes in glucose and PHB metabolism was demonstrated by metaproteomic and target protein analysis, implying that PHB-driven intracellular carbon accumulation could optimize the intracellular electron allocation and correspondingly promote nitrogen metabolism. Our work integrated the mechanisms of intracellular carbon metabolism with preferences for electron transfer pathways in denitrification, providing a new perspective on how the selective parameters regulated microbial functions involved in denitrification.
Asunto(s)
Desnitrificación , Pseudomonas stutzeri , Desnitrificación/fisiología , Pseudomonas stutzeri/metabolismo , Carbono/metabolismo , Nitratos/metabolismo , NAD/metabolismo , NADP/metabolismo , Oxígeno/metabolismo , Nitrógeno/metabolismo , Glucosa/metabolismoRESUMEN
The occurrence of nitrate is the most significant type of pollution affecting groundwater globally, being a major contributor to the poor condition of water bodies. This pollution is related to livestock-agricultural and urban activities, and the nitrate presence in drinking water has a clear impact on human health. For example, it causes the blue child syndrome. Moreover, the high nitrate content in aquifers and surface waters significantly affects aquatic ecosystems since it is responsible for the eutrophication of surface water bodies. A treatability test was performed in the laboratory to study the decrease of nitrate in the capture zone of water supply wells. For this purpose, two boreholes were drilled from which groundwater and sediments were collected to conduct the test. The goal was to demonstrate that nitrate in groundwater can be decreased much more efficiently using combined abiotic and biotic methods with micro-zero valent iron and biostimulation with lactic acid, respectively, than when both strategies are used separately. The broader implications of this goal derive from the fact that the separate use of these reagents decreases the efficiency of nitrate removal. Thus, while nitrate is removed using micro-valent iron, high concentrations of harmful ammonium are also generated. Furthermore, biostimulation alone leads to overgrowth of other microorganisms that do not result in denitrification, therefore complete denitrification requires more time to occur. In contrast, the combined strategy couples abiotic denitrification of nitrate with biostimulation of microorganisms capable of biotically transforming the abiotically generated harmful ammonium. The treatability test shows that the remediation strategy combining in situ chemical reduction using micro-zero valent iron and biostimulation with lactic acid could be a viable strategy for the creation of a reactive zone around supply wells located in regions where groundwater and porewater in low permeability layers are affected by diffuse nitrate contamination.
Asunto(s)
Compuestos de Amonio , Agua Subterránea , Contaminantes Químicos del Agua , Desnitrificación/fisiología , Ecosistema , Agua Subterránea/química , Hierro/química , Ácido Láctico , Nitratos/análisis , Óxidos de Nitrógeno , Agua , Contaminantes Químicos del Agua/análisisRESUMEN
The direct effect of CO2 on denitrification has attracted great attention currently. Our previous studies have confirmed that CO2 inhibited heterotrophic denitrification and caused high nitrite accumulation and nitrous oxide emission. Cysteine is a widely reported bio-accelerator; however, its effect on denitrification under CO2 exposure remains unknown. In this paper, the effect of cysteine on heterotrophic denitrification and its mechanisms under CO2 exposure were explored with the model denitrifier, Paracoccus denitrificans. We observed that total nitrogen removal increased from 17.9% to 90.4% as cysteine concentration increased from 0 to 50 µM, probably due to restoration of cell growth and viability. Further study showed that cysteine reduced the inhibition of CO2 on denitrification due to multiple positive influences: (1) regulating glutathione metabolism to eliminate intracellular reactive nitrogen species (RNS), while reducing extracellular polymeric substances (EPS) levels and altering its composition, ultimately restoring cell membrane integrity (2) facilitating the transport and metabolism of carbon sources to increase NADH production, and (3) increasing intracellular iron and up-regulating the expression of key iron transporters genes (AfuA, AfuB, ExbB and TonB) to restore the transport and consumption of electron. This study suggests that cysteine can be added to recover heterotrophic denitrification performance after inhibition by elevated CO2.
Asunto(s)
Carbono , Desnitrificación , Carbono/metabolismo , Dióxido de Carbono/farmacología , Cisteína/metabolismo , Desnitrificación/fisiología , Procesos Heterotróficos , Hierro/farmacología , Nitratos/metabolismo , Nitrógeno/metabolismo , Oxidación-ReducciónRESUMEN
Generally, high bioelectroactivity of anodophilic biofilm favors high power generation of microbial fuel cell (MFC); however, it is not clear whether it can promote denitrification of MFC synchronously. In this study, we studied the impact of anodophilic biofilm bioelectroactivity on the denitrification behavior of air-cathode MFC (AC-MFC) in steady state and found that high bioelectroactivity of anodophilic biofilm not only favored high power generation of the AC-MFC, but also promoted the growth of denitrifers at the anodes and strengthened denitrification. Anodophilic biofilms of AC-MFC with various bioelectroactivity were acclimated at conditions of open circuit (OC), Rext of 1000 Ω and 20 Ω (denoted as AC-MFC-OC, AC-MFC-1000Ω, and AC-MFC-20Ω, respectively) and performed for over 100 days. Electrochemical tests and microbial analysis results showed that the anode of the AC-MFC-20Ω delivered higher current response of both oxidation and denitrification and had higher abundance of electroactive bacteria than the AC-MFC-OC, AC-MFC-1000Ω, demonstrating a higher bioelectroactivity of the anodophilic biofilms. Moreover, these electroactive bacteria favored the accumulation of denitrifers, like Thauera and Alicycliphilus, probably by consuming trace oxygen through catalyzing oxygen reduction. The AC-MFC-20Ω not only delivered a 61.7% higher power than the AC-MFC-1000Ω, but also achieved a stable and high denitrification rate constant (kDN ) of 1.9 h-1 , which was 50% and 40% higher than that of the AC-MFC-OC and AC-MFC-1000Ω, respectively. It could be concluded that the high bioelectroactivity of the anodophilic biofilms not only favored high power generation of the AC-MFC, but also promoted the enrichment of denitrifers at the anodes and strengthened denitrification. This study provided an effective method for enhancing power generation and denitrification performance of the AC-MFC synchronously.
Asunto(s)
Fuentes de Energía Bioeléctrica/microbiología , Biopelículas , Desnitrificación/fisiología , Aire , Electrodos/microbiologíaRESUMEN
Nitrous oxide (N2 O) was previously deemed as a potent greenhouse gas but is actually an untapped energy source, which can accumulate during the microbial denitrification of nitric oxide (NO). Compared with the organic electron donor required in heterotrophic denitrification, elemental sulfur (S0 ) is a promising electron donor alternative due to its cheap cost and low biomass yield in sulfur-driven autotrophic denitrification. However, no effort has been made to test N2 O recovery from sulfur-driven denitrification of NO so far. Therefore, in this study, batch and continuous experiments were carried out to investigate the NO removal performance and N2 O recovery potential via sulfur-driven NO-based denitrification under various Fe(II)EDTA-NO concentrations. Efficient energy recovery was achieved, as up to 35.5%-40.9% of NO was converted to N2 O under various NO concentrations. N2 O recovery from Fe(II)EDTA-NO could be enhanced by the low bioavailability of sulfur and the acid environment caused by sulfur oxidation. The NO reductase (NOR) and N2 O reductase (N2 OR) were inhibited distinctively at relatively low NO levels, leading to efficient N2 O accumulation, but were suppressed irreversibly at NO level beyond 15 mM in continuous experiments. Such results indicated that the regulation of NO at a relatively low level would benefit the system stability and NO removal capacity during long-term system operation. The continuous operation of the sulfur-driven Fe(II)EDTA-NO-based denitrification reduced the overall microbial diversity but enriched several key microbial community. Thauera, Thermomonas, and Arenimonas that are able to carry out sulfur-driven autotrophic denitrification became the dominant organisms with their relative abundance increased from 25.8% to 68.3%, collectively.
Asunto(s)
Desnitrificación/fisiología , Microbiota , Óxido Nítrico , Óxido Nitroso , Azufre/metabolismo , Procesos Autotróficos/fisiología , Microbiota/genética , Microbiota/fisiología , Óxido Nítrico/química , Óxido Nítrico/metabolismo , Óxido Nitroso/análisis , Óxido Nitroso/metabolismoRESUMEN
Benthic N2 production by microbial denitrification and anammox is the largest sink for fixed nitrogen in the oceans. Most N2 production occurs on the continental shelves, where a high flux of reactive organic matter fuels the depletion of nitrate close to the sediment surface. By contrast, N2 production rates in abyssal sediments are low due to low inputs of reactive organics, and nitrogen transformations are dominated by aerobic nitrification and the release of nitrate to the bottom water. Here, we demonstrate that this trend is reversed in the deepest parts of the oceans, the hadal trenches, where focusing of reactive organic matter enhances benthic microbial activity. Thus, at â¼8-km depth in the Atacama Trench, underlying productive surface waters, nitrate is depleted within a few centimeters of the sediment surface, N2 production rates reach those reported from some continental margin sites, and fixed nitrogen loss is mainly conveyed by anammox bacteria. These bacteria are closely related to those known from shallow oxygen minimum zone waters, and comparison of activities measured in the laboratory and in situ suggest they are piezotolerant. Even the Kermadec Trench, underlying oligotrophic surface waters, exhibits substantial fixed N removal. Our results underline the role of hadal sediments as hot spots of deep-sea biological activity, revealing a fully functional benthic nitrogen cycle at high hydrostatic pressure and pointing to hadal sediments as a previously unexplored niche for anaerobic microbial ecology and diagenesis.
Asunto(s)
Sedimentos Geológicos/microbiología , Fijación del Nitrógeno/fisiología , Bacterias Fijadoras de Nitrógeno/metabolismo , Nitrógeno/metabolismo , Oxidación Anaeróbica del Amoníaco/fisiología , Desnitrificación/fisiología , Microbiota/fisiología , Nitratos/metabolismo , Nitrificación/fisiología , Ciclo del Nitrógeno/fisiología , Océanos y MaresRESUMEN
The naturally occurring biomineralization or microbially induced calcium carbonate (MICP) precipitation is gaining huge attention due to its widespread application in various fields of engineering. Microbial denitrification is one of the feasible metabolic pathways, in which the denitrifying microbes lead to precipitation of carbonate biomineral by their basic enzymatic and metabolic activities. This review article explains all the metabolic pathways and their mechanism involved in the MICP process in detail along with the benefits of using denitrification over other pathways during MICP implementation. The potential application of denitrification in building materials pertaining to soil reinforcement, bioconcrete, restoration of heritage structures and mitigating the soil pollution has been reviewed by addressing the finding and limitation of MICP treatment. This manuscript further sheds light on the challenges faced during upscaling, real field implementation and the need for future research in this path. The review concludes that although MICP via denitrification is an promising technique to employ it in building materials, a vast interdisciplinary research is still needed for the successful commercialization of this technique.
Asunto(s)
Bacterias , Biomineralización , Carbonato de Calcio , Materiales de Construcción/microbiología , Desnitrificación/fisiología , Bacterias/química , Bacterias/metabolismo , Carbonato de Calcio/química , Carbonato de Calcio/metabolismo , Redes y Vías Metabólicas , SueloRESUMEN
The imperfect denitrifier, Candidatus (Ca.) Desulfobacillus denitrificans, which lacks nitric oxide (NO) reductase, frequently appears in anammox bioreactors depending on the operating conditions. We used genomic and metatranscriptomic analyses to evaluate the metabolic potential of Ca. D. denitrificans and deduce its functional relationships to anammox bacteria (i.e., Ca. Brocadia pituitae). Although Ca. D. denitrificans is hypothesized to supply NO to Ca. B. pituitae as a byproduct of imperfect denitrification, this microbe also possesses hydroxylamine oxidoreductase, which catalyzes the oxidation of hydroxylamine to NO and potentially the reverse reaction. Ca. D. denitrificans can use a range of electron donors for denitrification, including aromatic compounds, glucose, sulfur compounds, and hydrogen, but metatranscriptomic analysis suggested that the major electron donors are aromatic compounds, which inhibit anammox activity. The interrelationship between Ca. D. denitirificans and Ca. B. pituitae via the metabolism of aromatic compounds may govern the population balance of both species. Ca. D. denitrificans also has the potential to fix CO2 via an irregular Calvin cycle and couple denitrification to the oxidation of hydrogen and sulfur compounds under chemolithoautotrophic conditions. This metabolic versatility, which suggests a mixotrophic lifestyle, would facilitate the growth of Ca. D. denitrificans in the anammox bioreactor.
Asunto(s)
Compuestos de Amonio/metabolismo , Oxidación Anaeróbica del Amoníaco/fisiología , Betaproteobacteria/metabolismo , Reactores Biológicos/microbiología , Desnitrificación/fisiología , Anaerobiosis , Dióxido de Carbono/metabolismo , Perfilación de la Expresión Génica , Glucosa/metabolismo , Compuestos Inorgánicos/metabolismo , Ácido Nítrico/metabolismo , Oxidación-Reducción , Planctomicetos/metabolismo , Compuestos de Azufre/metabolismo , Transcriptoma/genéticaRESUMEN
Certain facultative anaerobes such as the opportunistic human pathogen Pseudomonas aeruginosa can respire on nitrate, a process generally known as denitrification. This enables denitrifying bacteria to survive in anoxic environments and contributes, for example, to the formation of biofilm, hence increasing difficulties in eradicating P. aeruginosa infections. A central step in denitrification is the reduction of nitrite to nitric oxide by nitrite reductase NirS, an enzyme that requires the unique cofactor heme d1 . While heme d1 biosynthesis is mostly understood, the role of the essential periplasmatic protein NirF in this pathway remains unclear. Here, we have determined crystal structures of NirF and its complex with dihydroheme d1 , the last intermediate of heme d1 biosynthesis. We found that NirF forms a bottom-to-bottom ß-propeller homodimer and confirmed this by multi-angle light and small-angle X-ray scattering. The N termini are adjacent to each other and project away from the core structure, which hints at simultaneous membrane anchoring via both N termini. Further, the complex with dihydroheme d1 allowed us to probe the importance of specific residues in the vicinity of the ligand binding site, revealing residues not required for binding or stability of NirF but essential for denitrification in experiments with complemented mutants of a ΔnirF strain of P. aeruginosa. Together, these data suggest that NirF possesses a yet unknown enzymatic activity and is not simply a binding protein of heme d1 derivatives. DATABASE: Structural data are available in PDB database under the accession numbers 6TV2 and 6TV9.
Asunto(s)
Proteínas Bacterianas/química , Hemo/análogos & derivados , Periplasma/genética , Pseudomonas aeruginosa/genética , Secuencia de Aminoácidos , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Sitios de Unión , Clonación Molecular , Cristalografía por Rayos X , Desnitrificación/fisiología , Escherichia coli/genética , Escherichia coli/metabolismo , Eliminación de Gen , Expresión Génica , Vectores Genéticos/química , Vectores Genéticos/metabolismo , Hemo/biosíntesis , Hemo/química , Modelos Moleculares , Periplasma/química , Periplasma/enzimología , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , Multimerización de Proteína , Pseudomonas aeruginosa/química , Pseudomonas aeruginosa/enzimología , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Especificidad por Sustrato , TermodinámicaRESUMEN
Denitrification causes nitrogen losses from terrestrial ecosystems. The magnitude of nitrogen loss depends on the prevalence of denitrifiers, which show ecological differences if they harbour nirS or nirK genes encoding nitrite reductases with the same biological function. Thus, it is relevant to understand the mechanisms of co-existence of denitrifiers, including their response to environmental filters and competition due to niche similarities. We propose a framework to analyse the co-existence of denitrifiers across multiple assemblages by using nir gene-based co-occurrence networks. We applied it in Mediterranean soils before and during 1 year after an experimental fire. Burning did not modify nir community structure, but significantly impacted co-occurrence patterns. Bacteria with the same nir co-occurred in space, and those with different nir excluded each other, reflecting niche requirements: nirS abundance responded to nitrate and salinity, whereas nirK to iron content. Prior to fire, mutual exclusion between bacteria with the same nir suggested competition due to niche similarities. Burning provoked an immediate rise in mineral nitrogen and erased the signals of competition, which emerged again within days as nir abundances peaked. nir co-occurrence patterns can help infer the assembly mechanisms of denitrifying communities, which control nitrogen losses in the face of ecological disturbance.
Asunto(s)
Bacterias/metabolismo , Desnitrificación/fisiología , Incendios , Nitrito Reductasas/genética , Nitrito Reductasas/metabolismo , Bacterias/genética , Desnitrificación/genética , Ecosistema , Nitratos/metabolismo , Nitrógeno/metabolismo , Salinidad , Suelo/química , Microbiología del SueloRESUMEN
Nitrogen and phosphorous are important inorganic water pollutants that pose a major threat to the environment and health of both humans and animals. The physical and chemical ways to remove these pollutants from water and soil are expensive and harsh, so biological removal becomes the method of choice to alleviate the problem without any side effects. The identification of microorganisms capable of simultaneous heterotrophic nitrification and aerobic denitrification has greatly simplified the sequestration of nitrogen from ammonium (NH4+) into dinitrogen (N2). Further, the discovery of phosphorous accumulating organisms offers greater economic benefits because these organisms can favourably and simultaneously remove both nitrogen and phosphorous from wastewaters hence reducing the nutrient burden. The stability of the system and removal efficiency of inorganic pollutants can be enhanced by the use of immobilized organisms. However, limited work has been done so far in this direction and there is a need to further the efforts towards refining process efficiency by testing low-cost substrates and diverse microbial populations for the total eradication of these contaminants from wastewaters.
Asunto(s)
Desnitrificación/fisiología , Nitrificación/fisiología , Fosfatos/metabolismo , Purificación del Agua/métodos , Biodegradación Ambiental , Contaminantes Ambientales , Procesos Heterotróficos , Inmovilización , Nitrógeno/análisis , Fósforo , Aguas ResidualesRESUMEN
Factors influencing production of greenhouse gases nitrous oxide (N2O) and nitrogen (N2) in arable soils include high nitrate, moisture and plants; we investigate how differences in the soil microbiome due to antecedent soil treatment additionally influence denitrification. Microbial communities, denitrification gene abundance and gas production in soils from tilled arable plots with contrasting fertilizer inputs (no N, mineral N, FYM) and regenerated woodland in the long-term Broadbalk field experiment were investigated. Soil was transferred to pots, kept bare or planted with wheat and after 6 weeks, transferred to sealed chambers with or without K15NO3 fertilizer for 4 days; N2O and N2 were measured daily. Concentrations of N2O were higher when fertilizer was added, lower in the presence of plants, whilst N2 increased over time and with plants. Prior soil treatment but not exposure to N-fertiliser or plants during the experiment influenced denitrification gene (nirK, nirS, nosZI, nosZII) relative abundance. Under our experimental conditions, denitrification generated mostly N2; N2O was around 2% of total gaseous N2 + N2O. Prior long-term soil management influenced the soil microbiome and abundance of denitrification genes. The production of N2O was driven by nitrate availability and N2 generation increased in the presence of plants.
Asunto(s)
Desnitrificación/fisiología , Microbiología del Suelo , Suelo/química , Fertilizantes/análisis , Microbiota , Nitrógeno/análisis , Óxido Nitroso/análisis , PlantasRESUMEN
A salt-tolerant denitrifying bacterium strain F2 was isolated from seawall muddy water in Dalian City, Liaoning Province, China. Strain F2 was identified by morphological observations, physiological and biochemical characteristics and 16 S rDNA identification. The salt tolerance of strain F2 was verified and the factors affecting the removal ability of strain F2 to nitrous nitrogen (NO2-N) and nitrate nitrogen (NO3-N) in saline conditions were investigated. Strain F2 was identified as Alishewanella sp., named Alishewanella sp. F2. Strain F2 can tolerate NaCl concentrations up to 70 g/L, and its most efficient denitrification capacity was observed at NaCl concentrations of 0-30 g/L. In the medium with NaCl concentrations of 0-30 g/L, strain F2 exhibited high removal efficiencies of NO2-N and NO3-N, with the removal percentages for both NO2-N and NO3-N of approximately 99%. In saline conditions with 30 g/L NaCl, the optimum culture pH, NaNO2 initial concentrations and inoculation sizes of strain F2 were 8-10, 0.4-0.8 g/L and 5-7%, respectively. Strain F2 was highly effective in removing NO2-N and NO3-N in saline conditions, and it has a good application potential in saline wastewater treatment.
Asunto(s)
Alteromonadaceae/aislamiento & purificación , Desnitrificación/fisiología , Tolerancia a la Sal/genética , Aguas Residuales/microbiología , Alteromonadaceae/genéticaRESUMEN
Various sole and mixed electron donors were tested to promote the denitrification rate and nitrate removal efficiency in biofilter systems with high phosphate and ammonia removal efficiency (92.6% and 95.3% respectively). Compared to sole electron donors, complex organic carbon (bits of wood and straw) substantially improved the denitrification rate and nitrate removal efficiency (from 6.3%-18.5% to35.4%) by shifting the denitrifying microbial community composition, even though the relative abundance of functional genes mediating denitrification decreased. The mixed electron donor combining complex organic carbon with sulfur, iron and CH4 further promoted nitrate removal efficiency by 37.2%. The significantly higher abundance and diversity of bacteria mediating organic carbon decomposition in the treatments with complex organic carbon indicated the continuous production of organic carbon with small molecular weights, which provided sustainable and effective electron donor for denitrification. However, sole sulfur or iron did not effectively promote the denitrification rate and nitrogen removal efficiency, even though the related microbial community had been formed.