nitrite reduction
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2022 ◽  
Author(s):  
Valiallah Hosseininasab ◽  
Ida M. DiMucci ◽  
Pokhraj Ghosh ◽  
Jeffery A. Bertke ◽  
Siddarth Chandrasekharan ◽  
...  

Reduction of nitrite anions [NO2]- takes place in a myriad of environments such as in the soil as part of the biogeochemical nitrogen cycle as well as in acidified nuclear waste. Nitrite reduction typically takes place within the coordination sphere of a redox active transition metal. Lewis acid coordination, however, can dramatically modify the reduction potential of this polyoxoanion to allow for reduction under non-aqueous conditions (-0.74 V vs. NHE). This strategy enables the isolation of a borane-capped nitrite dianion [NO2]2- along with its spectroscopic study consistent with reduction to the N(II) oxidation state. Protonation of the nitrite dianion results in facile loss of nitric oxide (NO) while reaction of the nitrite dianion with nitric oxide results in disproportionation to nitrous oxide (N2O) and nitrite, connecting three redox levels in the global nitrogen cycle.


Author(s):  
Jiaqian Wang ◽  
Jie Liang ◽  
Peng-Yu Liu ◽  
Zhe Yan ◽  
Linxia Cui ◽  
...  

Electrochemical nitrite (NO2–) reduction reaction (NO2RR) is not only a promising strategy to degrade harmful NO2– contaminant in the environment but an attractive alternative to the Haber-Bosch process for sustainable...


2021 ◽  
Author(s):  
Francesca Petriglieri ◽  
Caitlin Singleton ◽  
Zivile Kondrotaite ◽  
Morten K. D. Dueholm ◽  
Elizabeth A. McDaniel ◽  
...  

Candidatus Accumulibacter was the first microorganism identified as a polyphosphate-accumulating organism (PAO), important for phosphorus removal from wastewater. This genus is diverse, and the current phylogeny and taxonomic framework appears complicated, with the majority of publicly available genomes classified as Candidatus Accumulibacter phosphatis, despite notable phylogenetic divergence. The ppk1 marker gene allows for a finer scale differentiation into different types and clades, nevertheless taxonomic assignments remain confusing and inconsistent across studies. Therefore, a comprehensive re-evaluation is needed to establish a common understanding of this genus, both in terms of naming and basic conserved physiological traits. Here, we provide this re-assessment using a comparison of genome, ppk1, and 16S rRNA gene-based approaches from comprehensive datasets. We identified 15 novel species, along with the well-known Ca. A. phosphatis, Ca. A. deltensis and Ca. A. aalborgensis. To compare the species in situ, we designed new species-specific FISH probes and revealed their morphology and arrangement in activated sludge. Based on the MiDAS global survey, Ca. Accumulibacter species were widespread in WWTPs with phosphorus removal, indicating the process design as a major driver for their abundance. Genome mining for PAO related pathways and FISH-Raman microspectroscopy confirmed the potential for the PAO metabolism in all Ca. Accumulibacter species, with detection in situ of the typical PAO storage polymers. Genome annotation further revealed fine-scale differences in the nitrate/nitrite reduction pathways. This provides insights into the niche differentiation of these lineages, potentially explaining their coexistence in the same ecosystem while contributing to overall phosphorus and nitrogen removal.


2021 ◽  
Vol 12 ◽  
Author(s):  
Lavinia Gambelli ◽  
Rob Mesman ◽  
Wouter Versantvoort ◽  
Christoph A. Diebolder ◽  
Andreas Engel ◽  
...  

Methylomirabilis bacteria perform anaerobic methane oxidation coupled to nitrite reduction via an intra-aerobic pathway, producing carbon dioxide and dinitrogen gas. These diderm bacteria possess an unusual polygonal cell shape with sharp ridges that run along the cell body. Previously, a putative surface protein layer (S-layer) was observed as the outermost cell layer of these bacteria. We hypothesized that this S-layer is the determining factor for their polygonal cell shape. Therefore, we enriched the S-layer from M. lanthanidiphila cells and through LC-MS/MS identified a 31 kDa candidate S-layer protein, mela_00855, which had no homology to any other known protein. Antibodies were generated against a synthesized peptide derived from the mela_00855 protein sequence and used in immunogold localization to verify its identity and location. Both on thin sections of M. lanthanidiphila cells and in negative-stained enriched S-layer patches, the immunogold localization identified mela_00855 as the S-layer protein. Using electron cryo-tomography and sub-tomogram averaging of S-layer patches, we observed that the S-layer has a hexagonal symmetry. Cryo-tomography of whole cells showed that the S-layer and the outer membrane, but not the peptidoglycan layer and the cytoplasmic membrane, exhibited the polygonal shape. Moreover, the S-layer consisted of multiple rigid sheets that partially overlapped, most likely giving rise to the unique polygonal cell shape. These characteristics make the S-layer of M. lanthanidiphila a distinctive and intriguing case to study.


2021 ◽  
Vol 8 ◽  
Author(s):  
Huan Wang ◽  
Meng Wang ◽  
Shen Fan ◽  
Jie Lu ◽  
Yi Lan ◽  
...  

Culture enrichment was developed to discover the uncharted microbial species in the environmental microbiota. Yet this strategy has not been widely used to study microbes of deep-sea environments. Here, we report the cultivation and metagenomic analysis of oceanic sediment microbiota collected from 6,477 m deep in the Mariana Trench. The sediment samples were cultured anaerobically in the laboratory for 4 months, before being subjected to full-length 16S rRNA gene sequencing using the PacBio technique and metagenome sequencing using both the Illumina and Oxford Nanopore techniques. The 16S rRNA gene analyses revealed 437 operational taxonomic units specific to the cultured microbes, despite the lower diversity of the cultured microbiota in comparison with the original. Metagenome analyses revealed the prevalence of functions related to respiration, energy production, and stress response in the cultured microbes, suggesting these functions may contribute to microbial proliferation under laboratory conditions. Binning of the assembled metagenome contigs of the cultured microbiota generated four nearly complete genomes affiliated to yet unclassified species under the genera Alcanivorax, Idiomarina, Sulfitobacter, and Erythrobacter. Excepting Alcanivorax, the other three genera were almost undetectable in the original samples and largely enriched in the cultured samples. The four genomes possessed a variety of genes for carbohydrate utilization and nitrite reduction, pointing to an ability to respire diverse carbon sources using nitrite as the final electron acceptor. Taken together, the findings suggest that a combination of culture enrichment and long-read sequencing is an ideal way to mine novel microbial species in the hadal environment, particularly species that are rare in their native environmental niches, and thus expand our understanding of the hadal microbial diversity and function.


2021 ◽  
Author(s):  
Guangyi Su ◽  
Moritz Lehmann ◽  
Jana Tischer ◽  
Yuki Weber ◽  
Jean-Claude Walser ◽  
...  

Anaerobic oxidation of methane (AOM) with nitrate/nitrite as the terminal electron acceptor may play an important role in mitigating methane emissions from lacustrine environments to the atmosphere. We investigated AOM in the water column of two connected but hydrodynamically contrasting basins of a south-alpine lake in Switzerland (Lake Lugano). The North Basin is permanently stratified with year-round anoxic conditions below 120 m water depth, while the South Basin undergoes seasonal stratification with the development of bottom water anoxia during summer. We show that below the redoxcline of the North Basin a substantial fraction of methane was oxidized coupled to nitrite reduction by Candidatus Methylomirabilis. Incubation experiments with 14CH4 and concentrated biomass from showed at least 43-52%-enhanced AOM rates with added nitrate/nitrite as electron acceptor. Multiannual time series data on the population dynamics of Candidatus Methylomirabilis in the North Basin following an exceptional mixing event in 2005/2006 revealed their requirement for lasting stable low redox-conditions to establish. In the South Basin, on the other hand, we did not find molecular evidence for nitrite-dependent methane oxidizing bacteria. Our data suggest that here the dynamic mixing regime with fluctuating redox conditions is not conducive to the development of a stable population of relatively slow-growing Candidatus Methylomirabilis, despite a hydrochemical framework that seems more favorable for nitrite-dependent AOM than in the North Basin. We predict that the importance of N-dependent AOM in freshwater lakes will likely increase in future because of longer thermal stratification periods and reduced mixing caused by global warming.


Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2266
Author(s):  
Karnjana Ruen-Pham ◽  
Linda E. Graham ◽  
Anchittha Satjarak

Cladophora is an algal genus known to be ecologically important. It provides habitats for microorganisms known to provide ecological services such as biosynthesis of cobalamin (vitamin B12) and nutrient cycling. Most knowledge of microbiomes was obtained from studies of lacustrine Cladophora species. However, whether lotic freshwater Cladophora microbiomes are as complex as the lentic ones or provide similar ecological services is not known. To illuminate these issues, we used amplicons of 16S rDNA, 18S rDNA, and ITS to investigate the taxonomy and diversity of the microorganisms associated with replicate Cladophora samples from three sites along the Nan River, Thailand. Results showed that the diversity of prokaryotic and eukaryotic members of Cladophora microbiomes collected from different sampling sites was statistically different. Fifty percent of the identifiable taxa were shared across sampling sites: these included organisms belonging to different trophic levels, decomposers, and heterotrophic bacteria. These heterogeneous assemblages of bacteria, by functional inference, have the potential to perform various ecological functions, i.e., cellulose degradation, cobalamin biosynthesis, fermentative hydrogen production, ammonium oxidation, amino acid fermentation, dissimilatory reduction of nitrate to ammonium, nitrite reduction, nitrate reduction, sulfur reduction, polyphosphate accumulation, denitrifying phosphorus-accumulation, and degradation of aromatic compounds. Results suggested that river populations of Cladophora provide ecologically important habitat for microorganisms that are key to nutrient cycling in lotic ecosystems.


Author(s):  
Bicun Jiang ◽  
Liqin Han ◽  
Juntian Wang ◽  
Chang Lu ◽  
Yang Pan ◽  
...  

Abstract A Co/Ti electrode for nitrate reduction was prepared by electrode-deposition. In the single-compartment electrolysis cell, nitrate (100 mg/L) removal reached nearly 100% after 3 h electrolysis under the current density of 20 mA cm–2 by using the Co/Ti electrode as cathode, and the main reduction products were ammonium nitrogen (66.5%) and nitrogen gas (33.5%). This performance on nitrate removal was comparable to a Co3O4/Ti electrode, and the electroactivity of the Co/Ti electrode towards nitrite reduction was higher than that of a Co3O4/Ti electrode. The Co/Ti electrode exhibited an improved stability with 18.7% of mass loss and 25.5% of Co dissolution compared with the Co3O4/Ti electrode after ultrasonic interference. The presence of chlorine ion (1,000 mg/L) could promote the total nitrogen (TN) removal to approximately 100% after 3 h electrolysis because of the ammonium oxidation by the free chlorine produced from the anode. In the presence of calcium (50 mg/L) and phosphate (0.5 mg/L), the nitrate removal decreased from 85.4 ± 1.5 to 57.7 ± 3.5% after ten reuse cycles. This result suggests that Ca and P should be pre-removed before the electro-reduction of nitrate.


2021 ◽  
Author(s):  
Songliang Liu ◽  
Shuli Yin ◽  
Ziqiang Wang ◽  
You Xu ◽  
Xiaonian Li ◽  
...  

Abstract Carbon dioxide reduction reaction (CO2RR) is a promising technology for mitigating greenhouse gas emission and achieving carbon neutrality. However, coupling CO2RR with other reactions to produce high value-added chemicals remains a challenge. In this work, we report self-assembled nanofibers composed of ultra-thin AuCu alloy nanowires possessing a Boerdijk-Coxeter structure with (111)-dominant facets for the electrosynthesis of urea by coupling CO2RR with nitrite reduction reaction (NO2−RR). The rich structural defects and AuCu bimetallic alloy composition provide a large number of highly catalytically active sites. The constructed AuCu nanofibers display excellent urea synthesis performance in the electrolyte solution containing 0.01 M KNO2 with continuous drumming of CO2, achieving a high urea yield rate of up to 3889.6 µg h− 1 mg− 1cat. and a high Faraday efficiency of 24.7% at -0.9 V. This work provides a feasible method for the rational design of self-assembled bimetallic nanofibers for electrosynthesis of urea under ambient conditions.


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