Abundance Of Functional Genes Research Articles

Nitrogen Addition Increased the Greenhouse Gas Emissions of Permafrost Peatland Due to the Abundance of Soil Microbial Functional Genes Increasing in the Great Khingan Mountains, Northeast China

Permafrost peatlands are sensitive to changes in nitrogen levels because they are largely nitrogen-limited ecosystems. However, the microbial mechanisms by which the addition of nitrogen increases the emission of greenhouse gasses from permafrost peatlands remain unclear. This study was conducted to decipher the relationship between greenhouse gas emissions and soil microorganisms under nitrogen addition. Here, we performed a 154-day experimental investigation in order to assess the release of greenhouse gasses such as CO2, CH4, and N2O from the soils. Additionally, we examined the correlation between the rates of these gas emissions and the presence of crucial microbial functional genes in the soil. The results showed that the addition of low (0.01 g kg−1), medium (0.02 g kg−1), and high (0.04 g kg−1) levels of nitrogen increased the cumulative CO2 emissions by 2.35%–90.42%, respectively. The cumulative emissions of CH4 increased by 17.29%, 25.55% and 21.77%, respectively. The cumulative emissions of N2O increased 2.97, 7.49 and 7.72-fold. The addition of nitrogen increased the abundance of functional genes in the bacteria, fungi, methanogens, denitrifying bacteria, and nitrogen-fixing bacteria in soil by modifying abiotic soil variables and providing sufficient substrates for microorganisms. The results indicated that the addition of nitrogen can significantly promote the emission of greenhouse gasses by increasing the abundance of functional microbial genes in the soil of permafrost peatlands. These findings highlight the importance of considering nitrogen deposition and the nitrogen released from thawing permafrost when predicting the future greenhouse gasses emitted from permafrost peatlands.

Straw additive enhances manure compost quality by promoting diverse aerobic bacteria and unitary thermophilic fungi

Shortening the initial activation time and extending the duration of the thermophilic phase are key to improving compost product quality in cold-climate regions. This study set up three treatments that cattle manure (CM), manure with rice straw (MR), and manure with maize straw (MM) in the field with ambient temperature ranging from –6 to 7 ℃. Compared with traditional manure composting, composting with straw performed more effectively, and the effect of the addition of maize straw surpassed that of the addition of rice straw. Straw additives markedly increased the compost pile temperature and extended the thermophilic phase duration. In addition, straw addition improved compost product maturity, as indicated by the humic-like substance content, absorbance ratio, and germination index. To further illustrate this result, the microbial community structure during the composting process was studied. During the thermophilic phase, straw additives, especially maize straw, improved the formation of a diverse aerobic bacterial community and a unitary thermophilic fungal community, and promoted a stronger relationship between the bacterial and fungal communities, as revealed by co-inertia analysis. The abundance of functional genes indicated that straw addition increased the activities of organic carbon degradation and transformation. This study demonstrated the necessity of enhancing the interaction between thermophilic–aerobic bacteria and thermophilic fungi to improve compost product quality.

Enhancement of volatile fatty acids to extremely high content in fermentation of food waste: Optimization of conditions, microbial functional genes, and mechanisms

The engineering application of volatile fatty acids (VFA) production from food waste (FW) can significantly enhance resource utilization. Enhancing VFA production is crucial for advancing this engineering application. This study presented a economically-feasible method to achieve high VFA production from FW: Conducting fermentation at pH 9 and 37 ℃ with addition of 20 % anaerobic sludge significantly increased the conversion of FW to VFAs (80.56 g COD/L, accounting for 87.37 % of the soluble chemical oxygen demand), while also increasing the content of NH4+-N (2658.15 mg/L). Macrotranscriptomic sequencing showed that Anaerosalibacter, Amphibacillus, Wansuia, Clostridiisalibacter, unclassified Tissierellia, Massilibacterium, unclassified Bacteroidales, and Tissierellia were the key active microorganisms for VFA production. The expression abundance of functional enzymes and genes related to VFA production pathways increased during the fermentation. This study significantly advanced the practical application of VFA production from FW, offering both theoretical insights and bacterial resources.

Virus-prokaryote interactions assist pollutant removal in constructed wetlands

As a vital part of microbial communities, viruses in constructed wetlands (CWs) remain poorly explored, yet they could significantly affect pollutant removal. Here, two pilot-scale CWs were built to investigate the viral community under different hydraulic loading rates (HLRs) using in-depth metagenomic analysis. Gene-sharing networks suggested that the CWs were pools of unexplored viruses. A higher abundance of prokaryotic functional genes related to sulfur cycling and denitrification was observed in the higher HLR condition, which was associated with greater removal of total nitrogen and nitrate nitrogen compared to the lower HLR condition. Viruses also affect nitrogen pollutant removal by potentially infecting functional prokaryotes, such as denitrification bacteria and ammonia-oxidizing bacteria, and by providing auxiliary metabolic genes involved in sulfur and nitrogen cycling. These findings reveal the significance of viruses in pollutant removal in CWs and enhance the understanding of the relationship between engineering design parameters and performance from microbial perspectives.

Identify the key factors driving the lignocellulose degradation of litter along a forest succession chronosequence from the perspective of functional genes

The purpose of this paper was to discover the key factors driving the lignocellulose degradation in litter along a forest succession chronosequence from the perspective of functional genes. We investigated four natural successive stages of forests (white birch forest, broad-leaved mixed forest, coniferous-broad-leaved mixed forest, and mixed broadleaved-Korean pine forest). We determined the lignocellulose degradation of litter and the absolute abundance of related functional genes by using high-throughput-qPCR. There was strong degradation of cellulose content, hemicellulose, and lignin contents in the litter decomposition layer in the early and late stages of forest succession, respectively. Furthermore, forest succession changed microbial communities' succession and fungal Shannon diversity, and then enhanced the absolute abundance of lignocellulose-degrading genes and nitrogen-cycling genes. By network analysis, bacterial and fungal module 1 were key modules for producing lignocellulose-degrading genes and nitrogen cycling genes, while fungal module 2 was a key module for lignin-degrading genes. Fungi were strongly correlated with functional genes based on Procrustes analysis. Additionally, cellulose-degrading genes were the key factor driving the cellulose degradation in the early period of forest succession, while fungal diversity and composition were key drivers in promoting the degradation of lignin in the late period of forest succession. Our study provided insight into the mechanisms underlying the soil microbe-driven functional changes in nutrient cycling and an understanding of the decomposition kinetics of litter at a more microscopic level in the process of forest succession.

Internal mechanism of microbial nitrogen removal under prolonged low-temperature stress: A focus on microbial communities, metabolic pathways, and microbial function

Low temperature restricts the stable treatment of wastewater in alpine and high-altitude regions. However, the internal mechanism of microbial functional succession at low temperatures remains unknown. To illustrate the internal mechanism by which low temperatures affect wastewater treatment, high-throughput 16S and metagenomic sequencing were employed. Results revealed that microorganisms effectively removed pollutants under prolonged low-temperature stress (3–8 °C). The removal efficiencies forchemical oxygen demand, NH4+-N, and total nitrogen were 80.80 %–95.18 %, 87.91 %–99.82 %, and 32.67 %–69.88 %, respectively. The relative abundance of Nitrospira and Nitrosomonas increased by 102.50 % and 276.92 %, respectively. Additionally, the relative abundance of heterotrophic nitrobacteria, including Terrimonas, Rhodobacter, and Ferribacterium, increased significantly, with values increasing by 34.63 %, 22.04 %, and 129.64 %, respectively. These bacteria became dominant. Metagenomic analysis revealed that low temperatures can inhibit membrane transfer. However, the functional genes for electron production and electron carriers were upregulated, thus promoting the ability of microorganisms to metabolize nitrogen. Moreover, the abundance of functional genes involved in extracellular electron transfer (pili, c-type cytochromes, and flagella) increased, which improved the nitrogen removal capacity. This study provides novel perspectives on the internal mechanism of microbial nitrogen removal under prolonged low-temperature stress.

Metagenomic Analysis Reveals the Effects of Different Land Use Types on Functional Soil Phosphorus Cycling: A Case Study of the Yellow River Alluvial Plain

Phosphorus (P) is a crucial limiting nutrient in soil ecosystems, significantly influencing soil fertility and plant productivity. Soil microorganisms adapt to phosphorus deficiency and enhance soil phosphorus effectiveness through various mechanisms, which are notably influenced by land use practices. This study examined the impact of different land use types (long-term continuous maize farmland, abandoned evolving grassland, artificial tamarisk forests, artificial ash forests, and wetlands) on soil phosphorus-cycling functional genes within the Tanyang Forest Farm in a typical region of the Yellow River alluvial plain using macro genome sequencing technology. The gene cluster related to inorganic phosphorus solubilization and organic phosphorus mineralization exhibited the highest relative abundance across different land use types (2.24 × 10−3), followed by the gene cluster associated with phosphorus transport and uptake (1.42 × 10−3), with the lowest relative abundance observed for the P-starvation response regulation gene cluster (5.52 × 10−4). Significant differences were found in the physical and chemical properties of the soils and the relative abundance of phosphorus-cycling functional genes among various land use types. The lowest relative abundance of soil phosphorus-cycling functional genes was observed in forestland, with both forestland types showing significantly lower gene abundance compared to wetland, farmland, and grassland. Correlation analysis and redundancy analysis (RDA) revealed a significant relationship between soil physicochemical properties and soil phosphorus-cycling functional genes, with ammonium nitrogen, organic carbon, total nitrogen, and pH being the main environmental factors influencing the abundance of these genes, explaining 70% of the variation in their relative abundance. Our study reveals land use’s impact on soil phosphorus-cycling genes, offering genetic insights into microbial responses to land use changes.

Comparative analyses on nitrogen removal microbes and functional genes within anaerobic-anoxic-oxic and deoxidation ditch sewage-treating processes in Wuhan and Xi'an cities, China.

Anaerobic-anoxic-oxic (A2/O) and deoxidation ditch (DOD) processes are being increasingly preferred owing to their effectiveness in treating various wastes in wastewater treatment plants (WWTPs). Considering seasonal variations is crucial in optimizing treatment processes, ensuring compliance with regulations, and maintaining the overall efficiency and effectiveness of WWTPs. This study aimed to determine the influence of seasonality on nitrogen removing microbes and functional genes within A2/O and DOD processes in the humid Wuhan and semi-arid Xi'an cities, China. The physicochemical parameters of water quality were determined, and molecular and bioinformatic analyses of the bacterial community and nitrogen metabolism functional genes in the two different treatment processes of two WWTPs were performed over four seasons. Our analyses revealed a significant difference in all physicochemical parameters across all experimental groups (p < 0.05). At the genus level, the abundance of Dokdonella, one unidentified genus of Nitrospiraceae, Terrimonas, and one unidentified genus of Chloroflexi was the highest in all groups. Generally, warmer seasons exhibited higher biodiversity indices. The A2/O system exhibited higher values in terms of most nitrogen metabolism functional genes than those of the DOD sewage treatment system. In both WWTPs, the abundance of most genes in spring and summer were higher than that of autumn and winter seasons. Taken together, changes in temperature, caused by seasonal changes, may contribute to changes in abundance of nitrogen metabolic functional genes.

Bioremediation of nitrate in agricultural drainage ditches: Impacts of low-grade weirs on microbiomes and nitrogen cycle gene abundance

Artificial drainage is essential for the success of modern agriculture, but it can also accelerate the movement of nutrients, especially nitrate, from soil to surrounding and downstream water bodies. Removal of nitrate from agricultural drainage by using controlled drainage systems, such as ditches installed with low-grade weirs, has been shown to help reduce nutrient loading into watersheds. However, the effect of low-grade weirs varies greatly, likely due to the differences in climate, system designs (e.g., hydraulic characteristics), and the resulting variation in microbial structures and functions in the ditch. In this study, we analyzed the temporal and spatial dynamics of microbiomes in a paired ditch system with weir-installed and uninstalled (control) channels over two years by using the 16S rRNA gene amplicon sequencing and the high-throughput quantitative PCR targeting various N cycle-associated genes [the Nitrogen Cycle Evaluation (NiCE) chip]. The installation of the low-grade weir had a significant impact on the microbiome structure and the distribution of denitrifiers. Microbiome structures also differed significantly between the ditch inlets and the outlets. Denitrification functional genes were more abundant in the inlets than in the other locations and in the channel installed with a low-grade weir. Additionally, oxygenic denitrifiers that utilize nitric oxide dismutase (nod) to produce N2 and O2 gases from nitric oxide were detected in the ditch channels, suggesting the occurrence of nitrate removal process that bypasses the production of nitrous oxide (N2O). The ditch microbiomes sampled during high-flow seasons (i.e., spring and fall) exhibited greater similarity to each other than microbiomes sampled during low-flow seasons (i.e., summer). Taken together, this study indicates that the low-grade weirs have the potential to foster a more favorable environment for denitrifiers, resulting in an increase in the abundance of denitrification functional genes. These findings could offer valuable insights into system management and optimization strategies.

Seasonal stability of the rumen microbiome contributes to the adaptation patterns to extreme environmental conditions in grazing yak and cattle

BackgroundThe rumen microbiome plays an essential role in maintaining ruminants’ growth and performance even under extreme environmental conditions, however, which factors influence rumen microbiome stability when ruminants are reared in such habitats throughout the year is unclear. Hence, the rumen microbiome of yak (less domesticated) and cattle (domesticated) reared on the Qinghai-Tibetan Plateau through the year were assessed to evaluate temporal changes in their composition, function, and stability.ResultsRumen fermentation characteristics and pH significantly shifted across seasons in both cattle and yak, but the patterns differed between the two ruminant species. Ruminal enzyme activity varied with season, and production of xylanase and cellulase was greater in yak compared to cattle in both fall and winter. The rumen bacterial community varied with season in both yak and cattle, with higher alpha diversity and similarity (beta diversity) in yak than cattle. The diversity indices of eukaryotic community did not change with season in both ruminant species, but higher similarity was observed in yak. In addition, the similarity of rumen microbiome functional community was higher in yak than cattle across seasons. Moreover, yak rumen microbiome encoded more genes (GH2 and GH3) related to cellulose and hemicellulose degradation compared to cattle, and a new enzyme family (GH160) gene involved in oligosaccharides was uniquely detected in yak rumen. The season affected microbiome attenuation and buffering values (stability), with higher buffering value in yak rumen microbiome than cattle. Positive correlations between antimicrobial resistance gene (dfrF) and CAZyme family (GH113) and microbiome stability were identified in yak, but such relationship was negatively correlated in cattle.ConclusionsThe findings of the potential of cellulose degradation, the relationship between rumen microbial stability and the abundance of functional genes varied differently across seasons and between yak and cattle provide insight into the mechanisms that may underpin their divergent adaptation patterns to the harsh climate of the Qinghai-Tibetan Plateau. These results lay a solid foundation for developing strategies to maintain and improve rumen microbiome stability and dig out the potential candidates for manufacturing lignocellulolytic enzymes in the yak rumen to enhance ruminants’ performance under extreme environmental conditions.

Effects of Different Fertilization Measures on Bacterial Community Structure in Seed Production Corn Fields

Different fertilization measures affect the soil’s physical and chemical properties and bacterial community structure, which in turn affects the growth environment and yield of maize seed production. Therefore, rational fertilization measures are important in maintaining and improving soil fertility and promoting maize crop growth. Research on fertilization practices in maize fields for seed production can help to increase agricultural productivity while protecting and enhancing soil health and achieving sustainable agricultural development. To clarify the effects of different fertilization measures on soil bacterial communities in seed corn fields, 16S rRNA high-throughput sequencing technology and PICRUSt method were used to explore the soil under different fertilization measures (CK as control, effects of single application of liquid organic fertilizer (M), single application of bacterial agents (BF), and combined application of liquid organic fertilizer and bacterial agents (M + BF)) on soil bacterial community structure characteristics and ecological functions. Proteobacteria (20.14–25.30%), Actinobacteriota (18.21–20.47%), Actinobacteriota (13.55–22.00%), and Chloroflexi (14.24–17.59%) were the dominant phyla. Bacillus, RB41, Arthrobacter, and Sphingomonas were the dominant genera. M + BF treatment significantly increased the relative abundance of Planctomycetota. The relative abundance of Bacillus and PaeniBacillus in M treatment decreased considerably, while the relative abundance of Turicibacter increased significantly. The relative abundance of Sphingomonas was reduced considerably in M and M + BF treatments. The relative abundance of Subgroup 10 decreased significantly after BF and M + BF treatments. BF treatment significantly increased the relative abundance of Skermanella. Redundancy analysis showed that alkali-hydrolyzed nitrogen (p = 0.044) was the main environmental factor affecting soil bacterial communities under different fertilizer treatments. PICRUSt function prediction results showed that metabolism was the main functional component of bacteria, accounting for 78.45–78.94%. The abundance of functional genes for terpenoid and polyketone metabolism, the endocrine system, the excretory system, and the immune system of the soil bacterial community was significantly increased under M treatment, while the abundance of functional genes for the digestive system was decreased considerably. Different fertilizer cultivation measures changed soil bacterial community composition and ecological function in maize fields. These results can provide a theoretical reference for the study of bacterial community succession characteristics in maize fields and the determination of appropriate fertilizer cultivation measures.

Warm growing season activates microbial nutrient cycling to promote fertilizer nitrogen uptake by maize

The influence of nitrogen (N) inputs on soil microbial communities and N uptake by plants is well-documented. Seasonal variations further impact these microbial communities and their nutrient-cycling functions, particularly within multiple cropping systems. Nevertheless, the combined effects of N fertilization and growing seasons on soil microbial communities and plant N uptake remain ambiguous, thereby constraining our comprehension of the optimal growing season for maximizing crop production. In this study, we employed 15N isotope labeling, high-throughput sequencing, and quantitative polymerase chain reaction (qPCR) techniques to investigate the effects of two distinct growing seasons on microbial communities and maize 15N uptake ratios (15NUR). Our results showed that the warm growing season (26.6 °C) increased microbial diversity, reduced network complexity but enhanced stability, decreased microbial associations, and increased modularization compared to the cool growing season (23.1 °C). Additionally, the warm growing season favored oligotrophic species and increased the abundance of microbial guilds and functional genes related to N, phosphorus, and sulfur cycling. Furthermore, alterations in the characteristics of soil microbial keystone taxa were closely linked to variations in maize 15NUR. Overall, our findings demonstrate significant seasonal variations in soil microbial diversity and functioning, with maize exhibiting higher 15NUR during the warm growing season of the double cropping system.

Increasing tree phylogenetic diversity stimulates microbial functional potential in a subtropical forest

Abstract Soil microbial functions are closely related to ecosystem productivity, carbon sequestration and their responses to global change. Tree phylogenetic diversity has been found to impact microbial community composition, diversity, and functions, but how it modulates the linkage between microbial community facets and functions remains unclear. Here, 45 plots covering a natural gradient of tree phylogenetic diversity (TPD) were selected in a subtropical forest of southwest China to explore how increasing TPD impacts soil microbial community facets and microbial functional potential. The microbial functional potential was evaluated based on the abundances of carbon, nitrogen, and phosphorus cycling-related functional genes. Soil fungal alpha diversity increased significantly, but bacterial alpha diversity did not change as TPD increased. Both soil microbial network complexity and stability improved significantly with increasing TPD. Ultimately, increasing TPD promoted soil microbial functional potential by stimulating soil carbon and nitrogen availability, microbial keystone diversity, and network stability collectively. These findings emphasize the critical roles of keystone taxa and network stability as microbial factors in stimulating soil microbial function in response to increasing TPD. Therefore, it is strongly recommended to increase TPD in order to stimulate soil microbial functions and other ecosystem functions when implementing afforestation or ecological restoration projects.

How biochar curbs the negative impacts of plastic mulching on soil enzymes and microorganisms while elevating crop yields in ridge-furrow systems

Ridge-furrow tillage is an important tillage and yield enhancement method used in dry farming areas; however, the spatial characteristics of the soil microenvironment under ridge-furrow tillage and the response of crop yields to mulching and biochar addition are not known. In this study, we conducted a three-year field experiment in which mulch and biochar, alone or combined, were introduced into ridge-furrow tillage system to explore their interactive effects on soil enzyme activities, bacterial communities, functional genes, and crop yields. The findings reveal significant spatial differences in soil physicochemical composition, enzyme activity, microbial communities, and functional genes under ridge-furrow tillage, which are further exacerbated by the addition of mulching and biochar. Under the premise of ridge-furrow tillage, both mulching and biochar addition reduce the α diversity of bacterial communities. Mulching simplifies the bacterial network, while biochar addition has the opposite effect. Mulching and biochar addition increase the relative abundance of carbon, nitrogen, and phosphorus functional genes and accelerate nutrient cycling, especially on the ridges. Mulching significantly improves crop yield but is detrimental to alkaline phosphatase activity and the abundance of the gene function. The addition of biochar mitigates the harm of mulching and further increases alfalfa yield. These findings not only provide scientific support for optimizing ridge-furrow tillage but also deepen our comprehensive understanding of the soil biochemical environment after the addition of mulching and biochar, further revealing their positive effects on yield formation.

Cow Dung Liquid Mulch Improves Maize Yields: Beneficial Microorganisms Are Enriched and Environmental Risks Are Reduced and Nutrient Cycling Is Promoted

Cow dung liquid mulch (CDLM), which uses cow dung as a raw material, has a good degradability and is a potential alternative to traditional plastic agricultural mulch, but there is a lack of research on the effects of CDLM on rhizosphere soil physicochemical properties, rhizosphere soil microbial functions, and crop yields. In this study, the link between maize yield, environmental factors, and functional genes as well as the responses of microbial community functions to CDLM and polyethylene mulch (PE) were studied using metagenomic sequencing. Functional annotation was also performed on clusters of orthologous groups of proteins, the Kyoto Encyclopedia of Genes and Genomes, and carbohydrate-active enzyme sequencing data. The results showed that CDLM significantly increased maize yield by 30.9% compared to CK while maintaining lower soil microplastic levels. CDLM promotes the enrichment of beneficial microorganisms such as Mycolicibacterium and Pseudomonas. The relative abundance of functional genes related to microbial metabolism, soil element cycling pathways, and organic matter degradation was significantly higher in CDLM than in CK. Microbial functional genes were positively correlated with maize yield and environmental factors such as soil nutrients. These results suggested that CDLM can improve maize yield by enriching beneficial microorganisms, reducing rhizosphere soil environmental risks, and enhancing rhizosphere soil microbial function. Rhizosphere soil nutrients and microbial functional genes together mediated the positive response of maize yield to CDLM. This study can provide a scientific basis and data support for the safe use of mulch in the future.

The combined nitrogen and phosphorus fertilizer application reduced soil multifunctionality in Qinghai-Tibet plateau grasslands, China

The impact of nitrogen (N) and phosphorus (P) fertilizer inputs on soil nutrient cycling and ecological function processes has garnered significant attention. Soil multifunctionality primarily refers to the soil's ability to perform multiple functions simultaneously, particularly the functions related to the genes involved in carbon (C), nitrogen (N), and phosphorus (P) cycles, which are critical for ecosystem sustainability. Despite this, the effects of N and P fertilizers on the expression of genes involved in soil carbon (C), nitrogen (N), and phosphorus (P) cycles, and their consequent influence on soil multifunctionality, remain unclear. To investigate this, we conducted a long-term nine-year experiment. The experimental site was fenced to prevent grazing and included four treatments: Control (no fertilizer), N (10 g N m−2 y−1, urea), P (5 g P m−2 y−1, Ca(H2PO4)2), and NP (10 g N and 5 g P m−2 y−1, urea and Ca(H2PO4)2). We examined the effects of these treatments on soil microbial functional gene abundance and multifunctionality. Our findings revealed that N addition altered the composition of soil microbial functional genes but did not affect functional diversity. Both N and P inputs, as well as their combination, negatively impacted soil carbon fixation and the genes encoding enzymes for the degradation of starch, hemicellulose, cellulose, and chitin. N input also disrupted soil nitrogen and phosphorus cycling by inhibiting the expression of soil denitrification genes (nirS and nosZ), phytate hydrolase gene (cphy), and a phosphatase gene (phoD). Additionally, P input significantly inhibited functional genes involved in soil nitrification, denitrification, ammonification, nitrogen fixation, and ammonia oxidation processes. It also adversely affected phytate synthesis and degradation. The combined N and P inputs had a substantial negative impact on soil nitrification (hao), denitrification (narG, nirK, nirS, and norZ), ammonification (gdh), nitrogen fixation, annamox, and nitrogen reduction, and inhibited the expression of soil phosphorus cycle genes. Long-term phosphorus application was found to have a more detrimental effect on soil multifunctionality compared to nitrogen application. Furthermore, our study showed that vegetation diversity and abundance are crucial drivers of soil carbon, nitrogen, and phosphorus cycling functional genes and multifunctionality. We concluded that N and P inputs alter soil multifunctionality by influencing vegetation diversity; therefore, maintaining vegetation diversity is essential for sustaining soil multifunctionality.

Unveiling the Hidden Responses: Metagenomic Insights into Dwarf Bamboo (Fargesia denudata) Rhizosphere under Drought and Nitrogen Challenges.

Dwarf bamboo (Fargesia denudata) is a crucial food source for the giant pandas. With its shallow root system and rapid growth, dwarf bamboo is highly sensitive to drought stress and nitrogen deposition, both major concerns of global climate change affecting plant growth and rhizosphere environments. However, few reports address the response mechanisms of the dwarf bamboo rhizosphere environment to these two factors. Therefore, this study investigated the effects of drought stress and nitrogen deposition on the physicochemical properties and microbial community composition of the arrow bamboo rhizosphere soil, using metagenomic sequencing to analyze functional genes involved in carbon and nitrogen cycles. Both drought stress and nitrogen deposition significantly altered the soil nutrient content, but their combination had no significant impact on these indicators. Nitrogen deposition increased the relative abundance of the microbial functional gene nrfA, while decreasing the abundances of nirK, nosZ, norB, and nifH. Drought stress inhibited the functional genes of key microbial enzymes involved in starch and sucrose metabolism, but promoted those involved in galactose metabolism, inositol phosphate metabolism, and hemicellulose degradation. NO3--N showed the highest correlation with N-cycling functional genes (p < 0.01). Total C and total N had the greatest impact on the relative abundance of key enzyme functional genes involved in carbon degradation. This research provides theoretical and technical references for the sustainable management and conservation of dwarf bamboo forests in giant panda habitats under global climate change.

Impact of water depth and flow velocity on organic matter removal and nitrogen cycling in floating constructed wetlands

The configuration of water depth (WD) and flow velocity (FV) in floating constructed wetlands (FCWs) reflects the complex interactions between hydraulic conditions and wastewater treatment performance. Properly configuring hydraulic conditions can optimize performance. This study explored the removal and degradation of organic matter and nitrogen (N) in FCWs with three different WDs (50 cm (SD), 70 cm (MD), and 95 cm (DD)) under four FV conditions (0, 0.3, 1.0, and 1.5 m/d). It also analyzed the regulatory effects of hydraulic conditions on microbial community structure to provide new insights for configuring hydraulic conditions in FCWs. The results indicate that variations in WD and FV do not significantly affect COD removal (p > 0.05), with removal efficiency (RE) consistently reaching 90 % across all conditions. However, hydraulic conditions do influence the degradation rate (k) of COD, with increased FV enhancing the k in MD and DD. In contrast, WD significantly impacts the removal of NH4+−N (p < 0.05), with RE in SD exceeding 80 % across all four FVs. The primary reason is that increased WD reduced the abundance of nitrifying bacteria (Nitrosomonas and Nitrospira) and functional genes (hao and pmoABC-amoABC). Meanwhile, increased WD and FV significantly enriched the denitrifying bacteria genera (such as Massilia, Bacillus, Ensifer, and Rhodobacter) and certain functional genes (nap and nir), favoring the denitrification process and enhancing the dissimilatory nitrate reduction to ammonium (DNRA) process. Furthermore, microbial community diversity, richness, and the number of operational taxonomic units (OTUs) were highest in SD, but decreased with increased WD. This is mainly related to changes in oxygen (O2) transmission and nutrient concentration. These findings help us understand the mechanisms by which hydraulic regulation affects the removal of organic matter and N in FCWs. They also propose potential solutions from a hydraulics perspective to enhance N removal.

Long‐term application of mineral fertilizer weakens the stability of microbial N‐transforming functions via the decrease of soil microbial diversity

AbstractIntroductionEnsuring functional stability is crucial for the sustainable development and soil health of agroecosystems amidst escalating climate changes. Although mineral fertilization is known to enhance the strength of soil N‐transforming functions, its effects on functional stability remain unclear.Materials &amp; MethodsThis study evaluated three stability components (resistance, resilience, and recovery), along with the dimensionality of soil microbial N‐transforming functions during drought‐rewetting process. We investigated enzymatic activity and functional gene abundances after 10 years of fertilization under three strategies, mineral fertilization (NPK), mineral fertilization plus organic amendments (OMN), and no fertilization (CK).ResultsThe resistance was 0.60, 0.66 and 0.56; the resilience was 0.46, 0.28 and 0.46; and the recovery was 0.83, 0.73 and 0.82, respectively in the CK, NPK and OMN treatments. Soils with long‐term mineral fertilization exhibited the highest resistance but the lowest resilience and recovery during drought‐rewetting. Furthermore, mineral fertilization demonstrated the lowest dimensionality of stability, with smallest ellipsoid volume and most negative correlations. Soil microbial alpha diversity was identified as a key predictor of functional stability, positively correlating with stability across fertilization strategies.ConclusionMineral fertilization, which decreased alpha diversity, posed challenges for sustainable development of agroecosystems under drought conditions. Mineral fertilization plus organic amendments provided strong N‐transforming functions and moderate stability, making it as an optimal fertilization strategy. These results offer valuable insights for optimizing agroecosystem management and advancing soil sustainability.

High-performance Multi-stage Baffled A2O Treatment Process for Domestic Sewage on Plateaus

At high altitudes, the low air pressure, low atmospheric oxygen content, and cryogenic environment during the cold season greatly limit the treatment efficiency of wastewater treatment plants (WWTPs). A novel pilot-plant configuration of the multi-stage baffled A2O wastewater treatment process was proposed and tested in Xizang. Different operational conditions involving at different influent loads and at low temperatures (10.0–11.0°C) were tested. When the influent flowrate increased to 4 m3∙d−1, the hydraulic retention time (HRT), internal and external reflux ratio, dissolved oxygen (DO), and aeration demands (gas to water ratio) all decreased to 34.2 h, 3.5/7, a stable 2.0–2.5 mg∙L−1, and 17.5, respectively. The effluent chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH+4−N), and total phosphorus (TP) all met the requirements of Class 1 Grade A of the China National Municipal Wastewater Discharge Standards (GB 18918-2002). The contribution of denitrifying phosphorus removal (DPR) to the removal of both nitrogen and phosphorus was over 50%. The alpha diversity and abundance of the top genera in the microbial community structure were both higher than the plateau WWTP. The reaction activity of the DPR process was significantly enhanced via the increased abundance of key functional genes within the metabolism pathway of ammonia-oxidizing bacteria (AOB) and nitrogen-oxidizing bacteria (NOB). The special multi-stage baffled structure featured a strategy of high sludge storage that improved the system tolerance for low temperatures and ensured favorable and stable performance for nitrogen and phosphorus removal at low temperatures. A short, periodic, and cyclically intermittent operation mode, with each cycle lasting only 20 minutes, effectively inhibited filamentous bacteria sludge bulking, resulting in a sludge volume index (SVI) that decreased to within 120 mL∙g−1 during the first 15 days of system start-up. A long sludge retention time (SRT) with no sludge discharging over 169 days and reduced aeration demands contributed to lower operation costs. The investigation revealed that the system had a high capacity for storing sludge phosphorus, possessing a TP content within a range of 23.45–28.99 mg∙g−1. This study provides a feasible solution for efficiently and economically treating wastewater in high-altitude areas.