Carbon Source Diversity Enhances Microbial Community Stability and Nitrogen Metabolism through Assembly Dynamics and Metabolic Interactions

The influence of wet-to-dry season shifts on the microbial community stability and nitrogen cycle in the Poyang Lake sediment

Advances in microbial nitrogen metabolism: synergizing technological innovations to drive systems biology and sustainable biotechnology.

Transforming heterotrophic to autotrophic denitrification process: Insights into microbial community, interspecific interaction and nitrogen metabolism

Impacts of aquaculture on nitrogen cycling and microbial community dynamics in coastal tidal flats.

Quorum sensing mediates spatiotemporal microbial community dynamics and nitrogen metabolism in biofloc-based Litopenaeus vannamei aquaculture systems.

Discharge from tributary pumping stations often impacts mainstream water quality, yet microbial communities and nitrogen metabolism in pumping station forebays remain poorly understood. Therefore, this study investigated the microbial community structure and nitrogen cycling mechanisms in sediments of tributary pumping station forebays within the Qinhuai River Basin using 16S rRNA and metagenomic sequencing. Results showed significant seasonal variations in the diversity and structure of sediment microbial communities, with higher diversity in spring than in winter. Genes associated with denitrification (e.g., narG, nirS, and nosZ) showed the highest abundance, suggesting that denitrification may be a key nitrogen transformation pathway. Co-occurrence network analysis revealed tighter associations between microbial taxa and nitrogen-cycling genes in spring, indicating more complex potential interactions during this season. The shift of network hubs across seasons suggested a seasonal succession of potential core functions related to nitrogen cycling. Redundancy analysis revealed that nitrate nitrogen (NO3--N), water temperature (WT), and ammonium nitrogen (NH4+-N) were the factors most strongly associated with microbial community variation, with WT showing the strongest association with functional gene distribution. Partial least squares path modeling revealed that seasonal variation had a significant positive association with denitrification gene abundance and a significant negative association with genes related to assimilatory nitrate reduction to ammonium and anaerobic ammonium oxidation. These findings improve our understanding of microbially mediated nitrogen cycling in pumping station forebays and provide a scientific basis for water quality management in river networks influenced by pumping station drainage.IMPORTANCEThis study is important because it reveals that pumping stations, which are key infrastructure in managed river systems, are not just hydraulic structures but dynamic bioreactors where microbial communities actively transform nitrogen. By demonstrating seasonal variations in microbial diversity and revealing a high denitrification potential, the research provides a mechanistic understanding of how nitrogen pollution is naturally mitigated in these engineered environments. Crucially, it pinpoints temperature as a primary regulator of these microbial functions. These insights allow water managers to proactively optimize pumping operations and design interventions that harness microbial activity, ultimately protecting downstream water quality from nutrient pollution in a changing climate.

Assessment of amino acid supplementation on rumen microbial efficiency and nitrogen metabolism using a continuous-culture system

The hybrid membrane catalytic biofilm reactor provides a new way of flue gas denitration. However, the effects of UV on denitrification performance, microbial community and microbial nitrogen metabolism are still unknown. In this study, the effects of UV on deNOx performance, nitrification and denitrification, microbial community and microbial nitrogen metabolism of a bench scale N-TiO2/PSF hybrid catalytic membrane biofilm reactor (HCMBR) were evaluated. The change from nature light to UV in the HCMBR leads to the fall of NO removal efficiency of HCMBR from 92.8% to 81.8%. UV affected the microbial community structure, but did not change microbial nitrogen metabolism, as shown by metagenomics sequencing method. Some dominant phyla, such as Gammaproteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, and Alphaproteobacteria, increased in abundance, whereas others, such as Proteobacteria and Betaproteobacteria, decreased. There were nitrification, denitrification, nitrogen fixation, and organic nitrogen metabolism in the HCMBR.

Microbial nitrogen metabolism is a complicated and key process in mediating environmental pollution and greenhouse gas emissions in rivers. However, the interactive drivers of microbial nitrogen metabolism in rivers have not been identified. Here, we analyze the microbial nitrogen metabolism patterns in 105 rivers in China driven by 26 environmental and socioeconomic factors using an interpretable causal machine learning (ICML) framework. ICML better recognizes the complex relationships between factors and microbial nitrogen metabolism than traditional linear regression models. Furthermore, tipping points and concentration windows were proposed to precisely regulate microbial nitrogen metabolism. For example, concentrations of dissolved organic carbon (DOC) below tipping points of 6.2 and 4.2 mg/L easily reduce bacterial denitrification and nitrification, respectively. The concentration windows for NO3--N (15.9-18.0 mg/L) and DOC (9.1-10.8 mg/L) enabled the highest abundance of denitrifying bacteria on a national scale. The integration of ICML models and field data clarifies the important drivers of microbial nitrogen metabolism, supporting the precise regulation of nitrogen pollution and river ecological management.

Clarifying the carbon–nitrogen coupling pattern in wetlands is crucial for understanding the driving mechanism of wetland carbon sequestration. However, the impacts of plants and environmental factors on the coupling of carbon–nitrogen in wetland sediments are still unclear. Sediment samples from plant (Typha angustifolia and Phragmites australis)-covered habitats and bare land were collected in two constructed wetlands in northern China. The contents of different forms of carbon and nitrogen in sediments and plants, and the sediment microbial community were detected. It was found that the sediment carbon to nitrogen (C/N) ratios did not differ significantly in the bare sites of different wetlands, but did in the plant-covered sites, which highlighted the different role of plants in shifting the carbon–nitrogen coupling in different constructed wetlands. The effects of plants on the sediment carbon–nitrogen coupling differed in two constructed wetlands, so the structural equation model was used and found that sediment microorganisms directly affected sediment C/N ratios, while water and sediment physicochemical properties indirectly affected sediment C/N ratios by altering sediment microbial functions. Multiple linear regression models showed that water pH, sediment moisture content, water dissolved oxygen, and water depth had a greater influence on the carbon metabolism potential of the sediment microbial community, while sediment moisture content had the greatest impact on the sediment microbial nitrogen metabolism potential. The study indicates that variations in environmental conditions could alter the influence of plants on the carbon and nitrogen cycles of wetland sediments. Water environmental factors mainly affect microbial carbon metabolism functions, while soil physicochemical factors, especially water content, affect microbial carbon and nitrogen metabolism functions.

Freeze-thaw aging and microbial colonization converts microplastics into nitrogen cycling hotspots.

Disclosing microbial nitrogen metabolism in groundwater via automated machine learning-based analysis: A fluorescence information-based approach.

The nitrogen cycle is the key to the healthy operation of river ecosystems and plays an important role in maintaining the ecological balance, purifying water quality, and promoting the circulation of material. The Xisha River was chosen as the research object to analyze the water quality condition from 2021 to 2023, and the microbial diversity of nitrogen metabolism, functional genes, and metabolic pathways in the water body were analyzed using macro-genomics technology. The results showed that total nitrogen (TN) was the main exceedance factor in the water body, and ammonia nitrogen (NH3-N), TN, and total phosphorus (TP) were the key factors affecting the water quality. The downstream station (W2) exhibited the most significant water quality changes, while the upstream station (W5) showed the highest biodiversity and abundance. The top five genera in abundance in the water body were unclassified__c__Actinomycetia, unclassified__p__Bacteroidota, Paenisporosarcina, Candidatus_Planktophila, and unclassified__c__Betaproteobacteria. The five most abundant nitrogen metabolism genes were K01915 (nitrate reductase), K00265 (nitrite reductase), K01673 (ammonium transporter), K00266 (nitrite reductase), and K02575 (nitrate reductase), each contributing to critical nitrogen cycling processes such as denitrification, nitrification, and nitrogen assimilation. The six major nitrogen metabolism pathways were denitrification (M00529), anisotropic nitrate reduction (M00528), anisotropic nitrate reduction (M00529). anisotropic nitrate reduction (M00530), complete nitrification (M00804), nitrate assimilation (M00615), methylaspartate cycling (M00740), and assimilatory nitrate reduction (M00531). TN was identified as the primary environmental factor influencing both microbial communities and nitrogen metabolism genes. Co-occurrence network analysis identified K01915 (nitrate reductase), K00459 (ammonium transporter), K01673 (ammonium transporter), and K00261 (nitrate reductase) as pivotal genes involved in nitrogen metabolism. This study reveals the microbial-driven nitrogen cycle and lays the foundation for mitigating nitrogen pollution in the Xisha River.

Taurine is a sulfur-containing nonproteinogenic amino acid. Recent studies have shown that taurine can improve rumen microbial crude protein (MCP) synthesis. This experiment aimed to investigate the action mechanisms of taurine on rumen MCP synthesis and nitrogen (N) metabolism in beef steers using sodium sulfate (Na2SO4) as a contrast. Six steers (bodyweight of 506 ± 17 kg) were assigned to three experimental groups including a basal diet (control), a basal diet supplemented with 45 g taurine/d or 50 g Na2SO4/d, and were allocated in a replicated 3 × 3 Latin square design. The amounts of sulfur from taurine and Na2SO4 were equal (11.38 g/d). The results showed that, compared with the control group, both taurine and Na2SO4 increased ruminal MCP concentration(P < 0.05) by 37.50% and 29.17%, respectively, and increased ruminal sulfide (S2−) concentration (P < 0.001). Both taurine and Na2SO4 increased neutral detergent fiber digestibility (P < 0.05). Taurine tended to increase (P = 0.087) while Na2SO4 decreased (P = 0.049) plasma urea concentration, while the taurine group exhibiting higher plasma urea concentration than the Na2SO4 group (P = 0.003). Compared with the control group, taurine did not affect urinary urea excretion (P = 0.246) whereas Na2SO4 decreased urinary urea excretion (P = 0.002) and both taurine and Na2SO4 increased urinary allantoin excretion (P < 0.05), total purine derivatives excretion (P < 0.05), and estimated rumen microbial N flow (P < 0.05). The urinary urea excretion of the taurine group was higher than the Na2SO4 group (P = 0.019). Compared with the control group, taurine did not affect N excretion, N retention (NR) or N utilization efficiency (NUE) (P > 0.10), but Na2SO4 decreased urinary N excretion (P = 0.018) and total N excretion (P = 0.024), and increased NR (P = 0.024) and NUE (P = 0.022). No differences were found in NR and NUE between the taurine and Na2SO4 groups (P > 0.10). Taurine improved ruminal MCP synthesis by enriching the pathways associated with sulfur and amino acid metabolism while Na2SO4 improved ruminal MCP synthesis by enriching pathways related to nucleotide and purine metabolism. In conclusion, both taurine and Na2SO4 improved ruminal MCP synthesis by modulating different pathways. Taurine was less effective in decreasing total N excretion than Na2SO4 but no differences in NR and NUE were found between the two treatments.

Recent studies have expanded the interests about microbial community and function following the rapid development of high-throughput sequencing techniques in the freshwater ecosystem. In this study, we aimed to attain a deep understanding of microbial community structure and potential nitrogen metabolism in Hulun Lake, a shallow hypereutrophic steppe lake in the Mongolian Plateau in China. The result demonstrated that cyanobacteria were the most dominant phylum. Network analysis showed both intra- and inter-phylum co-occurrence were pervasive, and there were modular structures in the microbial assemblages. The cluster dominated by proteobacteria was mainly negatively connected to the cluster dominated by both proteobacteria and actinobacteria. Cyanobacteria were tightly clustered together and positively connected to these two clusters. The major nitrogen metabolism pathways were glutamine synthetase-glutamate synthase and assimilatory nitrate reduction, indicating the nitrogen was mainly retained in the lake by microbial uptake. Cyanobacteria contributed 43.25% gene reads involved in the overall nitrogen metabolism but mainly contributed to assimilatory nitrate reduction and nitrogen fixation, aggravating the lake eutrophication. This study adds to our knowledge of microbial assemblages and nitrogen metabolism in the shallow hypereutrophic lake and provided an insight understanding for the purposes of lake ecosystem's protection and efficient management in the Mongolian Plateau.