Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Nitrogen transformation pathways”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

5 recordsLinked to original sources
PubMed2026

Integrated metagenomic and metaproteomic insights into current-carrying-coil magnetic field enhanced synergistic methanogenic system and antibiotic resistance gene reduction in cow manure anaerobic digestion.

Anaerobic digestion (AD) is a sustainable strategy for valorizing cow manure (CM). However, the high ammonia (NH3) concentration and low biodegradability of CM limit hydrolysis and methane production. This study investigated the application of a current-carrying-coil-based magnetic field (CCC-MF) to AD of CM. The CCC-MF digesters showed higher soluble chemical oxygen demand and attained 16.59 % higher ammonium nitrogen reduction, contributing to a 37.50 % higher average methane yield than the control. Further, CCC-MF digesters showed higher enzyme activities (alkaline protease + 30 %, acetate kinase + 22 % and hydrazine dehydrogenase + 26 %) and increased microbial metabolic indices (dehydrogenase activity + 17 % and electron transport system activity + 10 %) than the control. Metagenomics analysis revealed that abundances of the bacterial genera Mesotoga, Aminobacterium, Xiashengella, unclassified Candidatus Cloacimonadota, Advenella, Pseudomonas, and Comamonas increased, whereas the acetoclastic methanogen Methanothrix decreased by 2.58 %, accompanied by 2.07- and 1.64-fold increases in hydrogenotrophic methanogens Methanospirillum and Methanobacterium, respectively, in CCC-MF digesters. The abundance of nitrogen dissimilation and assimilation genes NirK, NorB, NarB, NapA, nmo, and GLT1 were enhanced by 1.14, 1.04, 2.30, 1.32, 1.17, and 1.29-fold in CCC-MF digesters compared to the control. Moreover, metaproteomics revealed higher up-regulated differentially expressed proteins in NH3 reduction-related amino acid metabolism pathways in CCC-MF digester compared to control. Additionally, reduced abundances of bacitracin, polymyxin, sulfonamide, and multidrug antibiotic resistance (MAR) gene types were observed in the CCC-MF digesters. The findings suggest that applying CCC-MF may be associated with higher methane production and ammonium reduction, potentially linked to a more favorable synergistic methanogenic system and nitrogen transformation pathways.

Manure↗
PubMed2026

Simultaneous removal of nitrogen, Cu2+, and bisphenol A in a hydrogel-biochar-AQDS immobilized bioreactor with added bicarbonate: Performance and metagenomic insights.

As the complexity of industrial wastewater pollution continues to increase, the simultaneous removal of nitrogen, metal contaminants, and persistent organic pollutants under low carbon conditions has become a key challenge for biological treatment systems. To address the operational instability and dependence on carbon sources observed in immobilized systems when exposed to copper (Cu2+) and bisphenol A (BPA), the Pseudoalteromonas japonicus strain LY0623 was integrated into a hydrogel-biochar-AQDS composite carrier to construct a multifunctional immobilized biofilm system. Notably, under conditions containing only NaHCO3, the R4 system achieved an NH4+-N removal rate of 89%. Under conditions where Cu2+ and BPA coexist, the R4 system achieved removal of NH4+-N (89%), NO3--N (100%), Cu2+ (85%), and BPA (88%). Sediment characterization confirmed that Cu2+ was immobilized through adsorption, complexation, and microbiologically induced carbonate precipitation (MICP). Metagenomic analysis further indicated that the Pseudomonadota phylum remained the dominant phylum, while functional pathways associated with inorganic carbon assimilation, HNAD nitrogen metabolism, endogenous carbon transformation, biomineralization, electron transfer, and aromatic compound degradation were preserved. By combining ammonia oxidation driven energy production, inorganic carbon utilization, redox mediated processes, and biomineralization, this study provides a highly promising low carbon strategy for treating industrial wastewater containing mixed pollutants.

Bisphenol A Compounds↗
PubMed2026

Unraveling anaerobic indole degradation in an acclimated sludge consortium: Candidate pathways and microbial division of labor inferred from metagenomic and metatranscriptomic analyses.

Indole is a widespread nitrogen-containing heterocyclic compound in manure, sludge, and wastewater systems, yet the enzymes and microbial populations involved in its anaerobic transformation remain poorly resolved. Here, we established a long-term acclimated anaerobic sludge consortium and combined degradation assays, metabolite profiling, metatranscriptomics, and genome-resolved metagenomics to investigate the functional basis of anaerobic indole degradation. After 120 days of acclimation, the consortium stably degraded 100 mg/L indole, whereas skatole was not effectively removed under the same strategy, indicating substrate-specific adaptation of the microbial community. Metabolite profiling detected oxindole, dioxindole, isatin, and anthranilic acid, supporting a putative transformation route involving pyrrole-ring oxidation and ring cleavage toward anthranilate-like intermediates. Metatranscriptomic analysis identified 16,660 differentially expressed genes after indole addition, with strong transcriptional responses involving oxidoreductases, hydrolases, cofactor-dependent redox metabolism, aromatic-CoA-related metabolism, and methane metabolism-associated pathways. Transcriptional responses highlighted the xanthine dehydrogenase-like molybdenum-enzyme system and isatin hydrolase as candidate contributors to upstream indole transformation, whereas those of abmG-like, bcrC, and oah genes were consistent with possible anthranilic acid activation and downstream CoA-type processing. MAG-resolved analysis further suggested that these candidate functions may be distributed among populations affiliated with Bacteroidota, Chloroflexota, Desulfobacterota, and Methanobacterium. Together, these findings establish a stable anaerobic indole-degrading consortium and provide a testable functional framework for syntrophic interactions linking upstream indole transformation, aromatic-CoA metabolism, and methanogenesis-associated carbon flow.

Anaerobic degradation↗
PubMed1979

[Pathways of enzymatic inactivation of levomycetin in El Tor vibrios with plasmid and chromosome resistance to the antibiotic].

Two possible mechanisms of enzymatic inactivation of levomycetin, i.e. acetylation of OH-groups and reduction of the n-nitrophenylic component by the cells and cell-free extracts of V. eltor 2044 with the plasmid or chromosome types of antibiotic resistance were studied in vitro. The vibrio containing the extrachromosome determinants were resistant to a number of antibiotics. The rate of levomycetin acetylation by them under conditions of intensive aeration and reduction of the antibiotic aromatic nitrogroup in the absence of oxygen was high. The cells with the chromosome resistance had a trace activity of levomycetin acetyltransferase. Still, they rather rapidly reduced levomycetin into its aminoderivative (during 2-hour incubation in the atmosphere of nitrogen 70-80% of the substrate are transformed into its summary arylamine). The antibiotic sensitive vibrio practically had no capacity for acetylation of levomycetin but could transform it into the reduced aminoderivative though to a less extent than the antibiotic resistant cells.

Acetylation↗
PubMed2026

Plant-derived and microbial biostimulants in sustainable agriculture: mechanisms, applications, and challenges.

Plant biostimulants have emerged as transformative and sustainable tools for improving crop productivity, resource-use efficiency, and resilience under rapidly intensifying environmental stresses. Unlike conventional agrochemicals, biostimulants function by activating physiological, biochemical, and molecular processes that optimize plant performance without directly supplying nutrients or exerting pesticidal effects. This review comprehensively examines the integrated roles of plant-derived and microbial biostimulants in sustainable agriculture, with particular emphasis on microbial-mediated mechanisms underlying plant stress adaptation and rhizosphere functioning. Plant-derived biostimulants, including seaweed extracts, humic substances, protein hydrolysates, amino acids, and chitosan, enhance nutrient acquisition, root architecture, hormonal regulation, and antioxidant defense systems. More importantly, microbial biostimulants, such as plant growth-promoting rhizobacteria (PGPR), endophytic microorganisms, mycorrhizal fungi, actinomycetes, yeasts, and cyanobacteria, exert multifunctional effects through biological nitrogen fixation, mineral solubilization, phytohormone biosynthesis, volatile signaling, osmolyte accumulation, pathogen suppression, and modulation of stress-responsive genes. These beneficial microorganisms reshape rhizosphere microbial communities, improve nutrient cycling, and enhance plant tolerance to drought, salinity, heat, and heavy metal toxicity. Emerging evidence from genomics, transcriptomics, metabolomics, and microbiome-based investigations has further revealed the molecular networks and signaling pathways governing biostimulant-induced resilience and plant-microbe interactions. Despite their substantial promise, inconsistent field performance, formulation instability, regulatory limitations, and inadequate mechanistic understanding continue to restrict their large-scale adoption. This review highlights recent advances in microbial and plant-derived biostimulants while identifying critical knowledge gaps and future opportunities for precision biostimulant engineering, microbiome manipulation, and climate-resilient crop management. The integration of next generation biostimulant technologies into sustainable agricultural systems may significantly reduce dependence on agrochemicals while improving crop productivity, environmental sustainability, and global food security.

Agriculture↗