Abundance Of Functional Genes Research Articles

Geographical factor dominates spatial patterns of potential nitrate reduction rates in coastal wetland sediments in Fujian Province, China

Nitrate (NO3−) reduction is a key process governing the nitrogen (N) dynamics of coastal wetland sediments. Although the effects of environmental factors on the NO3− reduction mechanism in coastal wetland sediments have been examined in various studies, the effects of spatial variation in potential NO3− reduction processes in coastal wetland sediments and the factors driving geographical variation in these processes have not been widely examined. Here, we conducted research on surface sediment samples from four different vegetation types at six coastal wetland sites across two regions. We characterized potential rates of NO3− reduction processes (including denitrification (DF), anammox (ANA), and dissimilatory nitrate reduction to ammonium (DNRA)) using a15N tracer method. Additionally, we assessed the abundances of functional genes, and microbial community structure using high-throughput sequencing, and metagenomic sequencing. In six wetland sites, the contribution ranges of DF, ANA, and DNRA to NO3− reduction were 38.43%–55.69%, 31.33%–45.65%, and 5.26%–17.11%, respectively, and potential NO3− reduction was mainly driven by N removal via gaseous N (DF+ANA). Significant spatial differences were observed in the structure of bacterial and fungal microbial communities, suggesting that geographical distance has a major effect on microbial community structure. Environmental factors and Functional gene abundances were significantly related to potential NO3− reduction processes, and physicochemical properties had a stronger effect on potential NO3− reduction processes than gene abundances. Factors showing significant differences across regions were the main drivers of variation in potential NO3− reduction processes. Overall, our study showed that sediment substrates and geographical environmental factors rather than the abundance of functional genes and vegetation types were the main indicators of potential NO3− reduction activities in coastal wetlands.

Microbial diversity and gene abundance in denitrifying bioreactors: A comparison of the woodchip surface biofilm versus the interior wood matrix.

Excessive amounts of nitrogen (N) and phosphorus (P) can lead to eutrophication in water sources. Woodchip bioreactors have shown success in removing N from agricultural runoff, but less is known regarding P removal. Woodchip bioreactors are subsurface basins filled with woodchips installed downgradient of agricultural land to collect and treat drainage runoff. Microorganisms use the woodchips as a carbon (C) source to transform N in the runoff, with unresolved biological impacts on P. This study aims to explore microbial communities present in the bioreactor and determine whether milling woodchips to probe the microbial communities within them reveals hidden microbial diversities or potential activities. Metagenomic sequencing and bioinformatic analyses were performed on six woodchip samples (i.e., three unmilled and three milled) collected from a 10-year-old woodchip bioreactor treating agricultural tile drainage. All samples had similar DNA purity, yield, quality, and microbial diversity regardless of milling. However, when sequences were aligned against various protein libraries, our results indicated greater relative abundance of denitrification and P transformation proteins on the outside of the woodchips (unmilled), while the interior of woodchips (milled) exhibited more functional gene abundance for carbohydrate breakdown. Thus, it may be important to characterize microbial communities both within woodchips, and on woodchip surfaces, to gain a more holistic understanding of coupled biogeochemical cycles on N, P, and C in woodchip bioreactors. Based on these findings, we advise that future microbial research on woodchips (and potentially other permeable organic materials) examine both the surface biofilm and the interior organic material during initial studies. Once researchers determine where specific proteins or enzymes of interest are most prevalent, subsequent studies may then focus on either one or both aspects, as needed.

The effects of graphene on low-temperature anammox process: The insights from short-term tests and long-term operation

Effluent quality deterioration caused by seasonal low temperature is a great challenge to the application of anammox technology. Here, the effects of different graphene materials on anammox process were investigated under both optimal temperature and low-temperature. The batch tests showed that at 30 °C, 300 mg/L of reduced graphene oxide‑sodium alginate gel (RGOSA) had the most significant promoting effect, reaching nitrogen removal efficiency (NRE) and nitrogen removal rate (NRR) of 95 % and 8.88 mgN/L/d, respectively. The changes of EPS secretion patterns and increasing of key enzymes activity might contribute to the enhanced anammox activity. During the long-term operation of anammox reactor, the NRE and NRR of the reactor decreased when the temperature dropped to 15 °C, showing an NRE of 50 %–57 % with the addition of 200 mg/L of reduced graphene oxide (RGO) and 40 %–45 % with the addition of 20 mg/L of RGO. Furthermore, specific anammox activity (SAA) of the RGO200 reactor at 15 °C increased by 57.1 % compared to the UASB reactor without graphene addition. Additionally, 16S rRNA and metagenomic analysis results revealed anammox bacteria Ca. Kuenenia was the dominant bacteria. Moreover, the RGO can significantly increase the relative abundance of N-converting functional genes. This study demonstrates the graphene materials can help anammox process adapting to low temperatures, providing a possible solution for the application of anammox technology.

Ex vivo metabolism kinetics of primary to secondary bile acids via a physiologically relevant human faecal microbiota model

Bile acids (BA) are synthesized in the human liver and undergo metabolism by host gut bacteria. In diseased states, gut microbial dysbiosis may lead to high primary unconjugated BA concentrations and significant perturbations to secondary BA. Hence, it is important to understand the microbial-mediated formation kinetics of secondary bile acids using physiologically relevant ex vivo human faecal microbiota models. Here, we optimized an ex vivo human faecal microbiota model to recapitulate the metabolic kinetics of primary unconjugated BA and applied it to investigate the formation kinetics of novel secondary BA metabolites and their sequential pathways. We demonstrated (1) first-order depletion of primary BA, cholic acid (CA) and chenodeoxycholic acid (CDCA), under non-saturable conditions and (2) saturable Michaelis-Menten kinetics for secondary BA metabolite formation with increasing substrate concentration. Notably, relatively lower Michaelis constants (Km) were associated with the formation of deoxycholic acid (DCA, 14.3 μM) and lithocholic acid (LCA, 140 μM) versus 3-oxo CA (>1000 μM), 7-keto DCA (443 μM) and 7-keto LCA (>1000 μM), thereby recapitulating clinically observed saturation of 7α-dehydroxylation relative to oxidation of primary BA. Congruently, metagenomics revealed higher relative abundance of functional genes related to the oxidation pathway as compared to the 7α-dehydroxylation pathway. In addition, we demonstrated gut microbial-mediated hyocholic acid (HCA) and hyodeoxycholic acid (HDCA) formation from CDCA. In conclusion, we optimized a physiologically relevant ex vivo human faecal microbiota model to investigate gut microbial-mediated metabolism of primary BA and present a novel gut microbial-catalysed two-step pathway from CDCA to HCA and, subsequently, HDCA.

Vertical Distribution Characteristics and Driving Factors of Bacterioplankton and Nitrogen Phosphorus Cycle Genes in Danjiangkou Reservoir

Danjiangkou Reservoir is a critical water source for the South-to-North Water Diversion Project, which harbors a diverse bacterioplankton community with varying depths, and the understanding of its nitrogen and phosphorus cycle and associated driving factors remains limited. In this study, we selected five ecological sites within Danjiangkou Reservoir and conducted metagenomics analysis to investigate the vertical distribution of bacterioplankton communities in the surface, middle, and bottom layers. Furthermore, we analyzed and predicted the function of nitrogen and phosphorus cycles, along with their driving factors. Our findings revealed the dominance of Proteobacteria, Actinobacteria, and Planctomycetes in the Danjiangkou Reservoir. Significant differences were observed in the structure of bacterioplankton communities across different depths, with temperature （T）, oxidation-reduction potential （ORP）, dissolved oxygen （DO）, and Chla identified as primary factors influencing the bacterioplankton composition. Analysis of nitrogen cycle functional genes identified 39 genes, including gltB, glnA, gltD, gdhA, NRT, etc., which were involved in seven main pathways, encompassing nitrogen fixation, nitrification, denitrification, and dissimilatory nitrate reduction. Phosphorus cycle function gene analysis identified 54 genes, including pstS, ppx-gppA, glpQ, ppk1, etc., primarily participating in six main pathways, including organic P mineralization, inorganic P solubilization, and regulatory. Cluster analysis indicated that different depths were significant factors influencing the composition and abundance of nitrogen and phosphorus cycle functional genes. The composition and abundance of nitrogen and phosphorus cycle functional genes in the surface and bottom layers differed and were generally higher than those in the middle layer. Deinococcus, Hydrogenophaga, Limnohabitans, Clavibacter, and others were identified as key species involved in the nitrogen and phosphorus cycle. Additionally, we found significant correlations between nitrogen and phosphorus cycle functional genes and environmental factors such as DO, pH, T, total dissolved solids （TDS）, electrical conductivity （EC）, and Chla. Furthermore, the content of these environmental factors exhibited depth-related changes in the Danjiangkou Reservoir, resulting in a distinct vertical distribution pattern of bacterioplankton nitrogen and phosphorus cycle functional genes. Overall, this study sheds light on the composition, function, and influencing factors of bacterioplankton communities across different layers of Danjiangkou Reservoir, offering valuable insights for the ecological function and diversity protection of bacterioplankton in this crucial reservoir ecosystem.

Insight into the effect of CaO2 addition on the prevalence and removal of antibiotic resistance genes during anaerobic sludge fermentation under ambient conditions

This study investigated the effect of CaO2 and its related hydrolysis products on the prevalence and removal of antibiotic resistance genes (ARGs) during anaerobic fermentation of waste activated sludge (WAS) under ambient conditions. Comprehensive analyses were conducted to elucidate the mechanisms underlying the effects of CaO2 addition, focusing on the microbial community structure, host bacteria, cell membrane permeability and the interaction between ARGs and environmental factors. Results showed the alkalinity, oxidation and calcium of CaO2 synergistically contributed to the elimination of ARGs. The top ARGs, such as sulI, sulII, tetC, tetX and ereA, were effectively reduced by 43.9–84.9 % with CaO2 addition during the ambient anaerobic fermentation. Ca(OH)2 treatment also shows good effectiveness in removing typical ARGs, followed by H2O2 treatment, while NaOH treatment increases ARGs abundance and raise the risk of their transmission. Among the influencing factors, the abundance and diversity of microbial community, organic matters, calcium and pH were the primary factors for ARGs migration. The effective reduction of Proteobacteria was an important reason for the removal of typical ARGs, particularly sulfonamide resistance genes. CaO2 also downregulated the relative abundance of autoinducer and functional genes related to outer membrane proteins (OMPs) and ARGs dissemination, thereby inhibiting ARGs transmission. This work provides a deep insight into the advantage of CaO2 in reducing ARGs, thus expanding its potential application in sludge treatment and ARGs elimination.

Deciphering taxonomic and functional patterns of microbial communities associated with the tiger tail seahorse (Hippocampus comes).

Gaining insight into the diversity, structure, and metabolic functions of microbial communities is essential for understanding their roles in host health and ecosystem dynamics. However, research on the seahorse-associated microbiome remains limited, despite these threatened fish facing increasing human pressures worldwide. Here, we explored the microbial diversity and metabolic functions of the skin and gut of the tiger tail seahorse (Hippocampus comes) and its surrounding environment using shotgun metagenomics and bioinformatics. Members of the Pseudomonadota phylum were dominant in the skin microbiome, whereas Bacteroidota was dominant in the gut. Bacillota, Actinomycetota, and Planctomycetota were also detected in the seahorse-associated microbiome. Statistical analysis revealed significant differences (P < 0.01) in species diversity between skin and gut microbiomes, with members belonging to the Moraxellaceae family being dominant on the skin and the Bacteroidaceae family in the gut. Moreover, the surrounding environment (water or sediment) did not have a direct effect on the seahorse microbiome composition. The skin microbiome exhibited a higher abundance of functional genes related to energy, lipid, and amino acid metabolism as well as terpenoids and polyketides metabolism, xenobiotics biodegradation, and metabolism compared with the gut. Despite differences among classes, the total abundance of bacteriocins was similar in both gut and skin microbiomes, which is significant in shaping microbial communities due to their antimicrobial properties. A better knowledge of seahorse microbiomes benefits conservation and sustainable aquaculture efforts, offering insights into habitat protection, disease management, and optimizing aquaculture environments, thereby promoting seahorse health and welfare while minimizing environmental impact and enhancing aquaculture sustainability.NEW & NOTEWORTHY To the best of our knowledge, this study represents the first comprehensive examination of the taxonomic and functional patterns of the skin and gut microbiome in the tiger tail seahorse. These findings have the potential to significantly enhance our understanding of the seahorse-associated microbiome, thereby contributing to the prediction and control of bacterial infections in seahorses, which are a leading cause of high mass mortality rates in seahorse aquaculture and other fish species.

PBAT microplastics exacerbates N2O emissions from tropical latosols mainly via stimulating denitrification

Biodegradable plastic mulching films are regarded as promising substitutes for their non-degradable counterparts to ameliorate serious plastic pollution in agriculture. Inevitably, biodegradable microplastics (BMs) can be formed and profoundly affect the function of soil ecosystems. However, little is known about the effects of BMs loading on soil nitrogen (N) dynamics and loss in tropical agricultural soils. Hereby, a 120-day soil incubation trial was performed to evaluate the effects of polybutylene adipate co-terephthalate (PBAT) microplastics on nitrous oxide (N2O) emissions, N transformation, and bacterial community structure in latosols. The results showed that PBAT addition raised soil ammonium nitrogen (NH4+–N) and dissolved organic carbon (DOC) contents, but lowered nitrate nitrogen (NO3––N) contents, accompanied with a smaller potential nitrification rate and a greater potential denitrification rate. The microbial biomass nitrogen and nrfA gene abundance were increased by PBAT, suggesting the processes of microbial N immobilization and dissimilatory nitrate reduction to ammonia were largely promoted. Positive correlations existed between N2O emissions and denitrification-related enzymatic activities and functional gene abundances (narG, nirK/S and Fungal nirK). PBAT amendment stimulated N2O emissions by 54.8 − 317.3 %, accompanied with increased values of those denitrification-related parameters, suggesting that stimulated denitrification was responsible for the exacerbated N2O emissions. Moreover, PBAT addition changed bacterial alpha diversity and bacterial community composition, where the relative abundances of Proteobacteria increased while those of Nitrospirae and Acidobacteria decreased. These findings are beneficial to understanding the fate of N in microplastics-polluted soil, which will provide a new insight into the impact of BMs on soil functions and environmental risks.

The Impact of Artificial Afforestation on the Soil Microbial Community and Function in Desertified Areas of NW China

Afforestation is a widely used method of controlling desertification globally as it significantly impacts the soil quality, microbial community structure, and function. Investigating the effects of various artificial vegetation restoration models on soil microbial communities is crucial in understanding the mechanisms involved in combating desertification. However, research on this topic in arid, desertified regions is limited. In this study, we collected soil samples from two types of artificial forests (single species and mixed species) and bare desert soils in desertified areas of Northwest China to explore the impact of afforestation on soil nutrients, the microbial community composition, network relationships, and carbohydrate degradation abilities using metagenomic sequencing techniques. Our findings indicate that afforestation significantly enhances the soil moisture, total carbon, available phosphorus, and total nitrogen levels. The soil under mixed-species forests exhibited significantly higher levels of total carbon, total phosphorus, available phosphorus, and total nitrogen than that under single-species forests. Following afforestation, the populations of Pseudomonadota, Acidobacteriota, and Cyanobacteria increased significantly, whereas Actinomycetota decreased markedly. In single-species forests, Pseudomonadota and Bacillota were enriched, whereas Chloroflexota, Planctomycetota, and Acidobacteriota were more prevalent in mixed-species plantations. Afforestation increases the complexity and stability of microbial community networks. Afforestation enhances microbial metabolic activity, particularly increasing the abundance of carbon degradation functional genes in forest soils compared to bare desert soils. Mixed-species plantations outperform single-species forests in enhancing carbohydrate metabolism, amino acid metabolism, and the biodegradation and metabolism of xenobiotics. The abundance of functional genes associated with the degradation of starch, cellulose, hemicellulose, chitin, and pectin in mixed-species forests was significantly greater than in single-species plantations. Our study shows that mixed-species afforestation effectively improves the soil quality, enhances the stability of soil microbial communities, and bolsters the carbon cycle in arid regions prone to desertification. The reciprocal relationship between microorganisms and plants may serve as an intrinsic mechanism by which mixed-species afforestation more effectively controls desertification.

Mitigation of ammonia and hydrogen sulfide emissions during aerobic composting of laying hen waste through NaOH-modified biochar

The impact of NaOH-modified biochar on the release of NH3 and H2S from laying hens' manure was examined for 44 days, using a small-scale simulated aerobic composting system. The findings revealed that the NaOH-modified biochar reduced NH3 and H2S emissions by 40.63% and 77.78%, respectively, compared to the control group. Moreover, the emissions of H2S were significantly lower than those of the unmodified biochar group (p < 0.05). The increased specific surface area and microporous structure of the biochar, as well as the higher content of alkaline and oxygenated functional groups, were found to facilitate the adsorption of NH3 and H2S. This enhanced adsorption capability was the primary reason for the significant reduction in NH3 emissions. Furthermore, during the high-temperature phase of composting, there was a notable alteration in the microbial community. The abundance of Limnochordaceae, Savagea, and IMCC26207 increased significantly which aided in the conversion of H2S to stable sulfate. These microorganisms also influenced the abundance of functional genes involved in sulfur metabolism, thereby inhibiting cysteine synthesis, along with the decomposition and conversion of sulfate to sulfite. This led to a significant decrease in H2S emissions. This study provides valuable data for the selection of deodorizers in the composting process of egg-laying hens. The results have significant implications for the application of NaOH-modified biochar for odor reduction in aerobic composting processes.

Mixotrophic aerobic denitrification facilitated by denitrifying bacterial-fungal communities assisted with iron in micro-polluted water: Performance, metabolic activity, functional genes abundance, and community co-occurrence

Low-dosage nitrate pollutants can contribute to eutrophication in surface water bodies, such as lakes and reservoirs. This study employed assembled denitrifying bacterial-fungal communities as bio-denitrifiers, in combination with zero-valent iron (ZVI), to treat micro-polluted water. Immobilized bacterial-fungal mixed communities (IBFMC) reactors demonstrated their ability to reduce nitrate and organic carbon by over 43.2 % and 53.7 %, respectively. Compared to IBFMC reactors, IBFMC combined with ZVI (IBFMC@ZVI) reactors exhibited enhanced removal efficiencies for nitrate and organic carbon, reaching the highest of 31.55 % and 17.66 %, respectively. The presence of ZVI in the IBFMC@ZVI reactors stimulated various aspects of microbial activity, including the metabolic processes, electron transfer system activities, abundance of functional genes and enzymes, and diversity and richness of microbial communities. The contents of adenosine triphosphate and electron transfer system activities enhanced more than 5.6 and 1.43 folds in the IBFMC@ZVI reactors compared with IBFMC reactors. Furthermore, significant improvement of crucial genes and enzyme denitrification chains was observed in the IBFMC@ZVI reactors. Iron played a central role in enhancing microbial diversity and activity, and promoting the supply, and transfer of inorganic electron donors. This study presents an innovative approach for applying denitrifying bacterial-fungal communities combined with iron enhancing efficient denitrification in micro-polluted water.

Green-house gas fluxes and soil microbial functional genes abundance in saturated and drained peatlands in South-West Iceland

The drainage of peatlands followed by land use conversion significantly impacts on the fluxes of green-house gases (GHGs, i.e. CO2, CH4, and N2O) to and from the atmosphere, driven by changes in soil properties and microbial communities.In this study, we compared saturated peatlands with drained ones used for sheep grazing or cultivated, which are common in South-West Iceland. These areas exhibit different degrees of soil saturation and nitrogen (N) content, reflecting the anthropic pressure gradient.We aimed at covering knowledge gaps about lack of estimates on N2O fluxes and drainage, by assessing the emissions of GHGs, and the impact of land conversion on these emissions. Moreover, we investigated soil microbial community functional diversity, and its connection with processes contributing to GHGs emission.GHGs emissions differed between saturated and drained peatlands, with increased soil respiration rates (CO2 emissions) and N mineralization (N2O), consistent with the trend of anthropogenic pressure. Drainage drastically reduced methane (CH4) emissions but increased CO2 emissions, resulting in a higher global warming potential (GWP). Cultivation, involving occasional tillage and fertilization, further increased N2O emissions, mediated by higher N availability and conditions favorable to nitrification. Functional genes mirrored the overall trend, showing a shift from prevalent methanogenic archaea (mcrA) in saturated peatlands to nitrifiers (amoA) in drained-cultivated areas.Environmental variables and nutrient content were critical factors affecting community composition in both environments, which overall affected the GHGs emissions and the relative contribution of the three gases.

Effects of Exocellobiohydrolase CBHA on Fermentation of Tobacco Leaves.

The quality of tobacco is directly affected by macromolecular content, fermentation is an effective method to improve biochemical properties. In this study, we utilized CBHA (cellobiohydrolase A) glycosylase, which was expressed by Pichia pastoris, as an additive for fermentation. The contents of main chemical components of tobacco leaves after fermentation were determined, and the changes of microbial community structure and abundance in tobacco leaves during fermentation were analyzed. The relationship between chemical composition and changes in microbial composition was investigated, and the function of bacteria and fungi in fermentation was predicted to identify possible metabolic pathways. After 48 h of CBHA fermentation, the contents of starch, cellulose and total nitrogen in tobacco leaf decreased by 17.60%, 28.91% and 16.05%, respectively. The microbial community structure changed significantly, with Aspergillus abundance decreasing significantly, while Filobasidum, Cladosporium, Bullera, Komagataella, etc., increased in CBHA treated group. Soluble sugar was most affected by microbial community in tobacco leaves, which was negatively correlated with starch, cellulose and total nitrogen. During the fermentation process, the relative abundance of metabolism-related functional genes increased, and the expressions of cellulase and endopeptidase also increased. The results showed that the changes of bacterial community and dominant microbial community on tobacco leaves affected the content of chemical components in tobacco leaves, and adding CBHA for fermentation had a positive effect on improving the quality of tobacco leaves.

Quorum sensing mediated response mechanism of anammox consortia to anionic surfactant: Molecular simulation and molecular evidence

The widespread use of surfactants raise challenges to biological wastewater treatment. Anaerobic ammonium oxidation (anammox) process has the potential to treat wastewater containing anionic surfactants, but the response of anammox consortia at the molecular level under long-term exposure is unclear. Using high-throughput sequencing and gene quantification, combined with molecular docking, the effect of sodium dodecyl sulfonate (SDS) on anammox consortia were investigated. Levels of reactive oxygen species (ROS) might be lower than the threshold of oxidative damage, while the increase of lactate dehydrogenase (LDH) represented the cell membrane damage. Decreased abundance of functional genes (hdh, hzsA and nirS) indicated the decrease of the anammox bacterial abundance. Trace amounts of N-acyl homoserine lactone (AHL, C6-HSL, C8-HSL and C12-HSL) contained in influent could induce endogenous quorum sensing (QS), which could regulate the correlation between functional bacteria to optimize the microbial community and strengthen the resistance of anammox consortia to SDS. In addition, the proliferation of disinfectant resistance genes might increase the environmental pathogenicity of sewage discharge. This work highlights the potential response mechanism of anammox consortium to surfactants and provides a universal microbial-friendly bioenhancement strategy based on QS.

The Application of Orychophragmus violaceus as a Green Manure Relieves Continuous Cropping Obstacles in Peanut Cultivation by Altering the Soil Microbial Community and Functional Gene Abundance

The Application of Orychophragmus violaceus as a Green Manure Relieves Continuous Cropping Obstacles in Peanut Cultivation by Altering the Soil Microbial Community and Functional Gene Abundance

Insight into mitigation mechanisms of N2O emission by biochar during agricultural waste composting

The effects and mitigation mechanisms of biochar added at different composting stages on N2O emission were investigated. Four treatments were set as follows: CK: control, BB10%: +10 % biochar at beginning of composting, BB5%&T5%: +5% biochar at beginning and + 5 % biochar after thermophilic stage of composting, BT10%: +10 % after thermophilic stage of composting. Results showed that treatment BB10%, BB5%&T5%, and BT10% reduced total N2O emissions by 55 %, 37 %, and 36 %, respectively. N2O emission was closely related to most physicochemical properties, while it was only related to amoA gene and hydroxylamine oxidoreductase. Different addition strategies of biochar changed the contributions of physicochemical properties, functional genes and enzymes to N2O emission. Organic matter and C/N contributed 23.7 % and 27.6 % of variations in functional gene abundances (P < 0.05), respectively. pH and C/N (P < 0.05) contributed 37.3 % and 17.3 % of variations in functional enzyme activities. These findings provided valuable insights into mitigating N2O emissions during composting.

Effect of biochar addition on the anaerobic digestion of food waste: microbial community structure and methanogenic pathways.

This study assessed the effects of the addition of biochar prepared at 700 °C with different dosages on the anaerobic digestion of food waste. The biochar addition at a concentration of 10.0 g/L increased the cumulative methane yield by 128%, and daily methane production was also significantly promoted. The addition of biochar derived from poplar sawdust significantly increased the relative abundance of dominant bacteria for anaerobic digestion by 85.54-2530% and promoted the degradation of refractory organic matter and the transfer of materials between the hydrolysis and acid production stages. Further analysis has demonstrated that Bathyarchaeia and hydrogenotrophic methanogens were enriched by the biochar addition. Meanwhile, the relative abundances of functional genes, including C5-branched dibasic acid metabolism, and pyruvate metabolism, were increased by 11.38-26.27%. The relative abundances of genes related to major amino acid metabolism, including histidine metabolism, lysine biosynthesis, and phenylalanine, tyrosine, and tryptophan biosynthesis, were increased by 11.96-15.71%. Furthermore, the relative abundances of genes involved in major replication and repair were increased by 14.76-22.76%, and the major folding, sorting, degradation, and translation were increased by 14.47-19.95%, respectively. The relative abundances of genes related to major membrane transport and cell motility were increased by 10.02 and 83.09%, respectively.

Inhibition of phosphorus removal performance in activated sludge by Fe(III) exposure: transitions in dominant metabolic pathways.

Simultaneous chemical phosphorus removal process using iron salts (Fe(III)) has been widely utilized in wastewater treatment to meet increasingly stringent discharge standards. However, the inhibitory effect of Fe(III) on the biological phosphorus removal system remains a topic of debate, with its precise mechanism yet to be fully understood. Batch and long-term exposure experiments were conducted in six sequencing batch reactors (SBRs) operating for 155 days. Synthetic wastewater containing various Fe/P ratios (i.e., Fe/P = 1, 1.2, 1.5, 1.8, and 2) was slowly poured into the SBRs during the experimental period to assess the effects of acute and chronic Fe(III) exposure on polyphosphate-accumulating organism (PAO) growth and phosphorus metabolism. Experimental results revealed that prolonged Fe(III) exposure induced a transition in the dominant phosphorus removal mechanism within activated sludge, resulting in a diminished availability of phosphorus for bio-metabolism. In Fe(III)-treated groups, intracellular phosphorus storage ranged from 3.11 to 7.67 mg/g VSS, representing only 26.01 to 64.13% of the control. Although the abundance of widely reported PAOs (Candidatus Accumulibacter) was 30.15% in the experimental group, phosphorus release and uptake were strongly inhibited by high dosage of Fe(III). Furthermore, the abundance of functional genes associated with key enzymes in the glycogen metabolism pathway increased while those related to the polyphosphate metabolism pathway decreased under chronic Fe(III) stress. These findings collectively suggest that the energy generated from polyhydroxyalkanoates oxidation in PAOs primarily facilitated glycogen metabolism rather than promoting phosphorus uptake. Consequently, the dominant metabolic pathway of communities shifted from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism as the major contributor to the decreased biological phosphorus removal performance.

Impact of two acquisitive plants on N cycle on different soils: The invasive Fallopia japonica does it and so does the native Dactylis glomerata!

Invasive plants may alter ecological and ecosystem processes, including the N-cycle. The Fallopia species complex is a well-studied invasive species whose N-resource acquisition traits define it as an acquisitive species. However, the study of the impacts of invasive plants on the N-cycle never considers the N-acquisition strategy as a reference for choosing another suitable plant control. The purpose of this study is to assess the impacts of an invasive species (Fallopia japonicaFJ) on the N-cycle and to compare with those caused by a native acquisitive species (Dactylis glomerataDG), all compared to unplanted soils. A four-months mesocosm experiment was conducted by growing FJ and DG on nine different soils and measuring their impacts on N-cycle microbial activities (free-living nitrogen fixation FLNF, denitrification DEA, nitrification NEA), on N-mineral forms and on functional N-cycle gene abundance (nifH, AOA, AOB, nirS, nirK) as well as the total bacterial community gene (rRNA 16S). The nine soils differ in microbial enzymatic activities, N-mineral form concentrations, physico-chemical factors, texture, and gene abundances. Plant effects on FLNF, NEA and DEA are only soil dependent and no effect of invasive status was found. In addition, the native plant DG generally affected microbial parameters over a wider range of soils than the invasive plant. Stronger impacts of the native DG on microbial gene abundances were found compared to the invasive FJ. A stronger effect of the invasive plant was found for the soil NO3− concentration, with a significant decrease under the FJ than under the DG. Under both FJ and DG, NH4+ concentrations were not significantly affected. In conclusion, the invasive status in the ecosystem of the two plants studied cannot be explained through their impacts on microbial enzymatic activities and gene abundances of the soil N-cycle and the soil N mineral pools.

Synthetic Microbial Community Promotes Bacterial Communities Leading to Soil Multifunctionality in Desertified Land.

Soil desertification is an important challenge in global soil management, and effectively and stably restoring soil function is an urgent problem. Using synthetic microbial communities (SynComs) is a burgeoning microbial strategy aimed at enhancing soil nutrients through functional synergies among diverse microorganisms; nevertheless, their effectiveness in restoring desertified soils remains unknown. In this study, we conducted a two-year field experiment using a SynCom constructed by in situ probiotic bacteria and set up control, chemical fertilizer, and combined SynCom-chemical fertilizer (combined fertilizer) treatments to investigate the linkage between microbial communities and soil multifunctionality in the soil surface layer (0-10 cm). Both the bacterial and fungal communities differed the most under the combined fertilizer treatment compared to the control. The bacterial communities differed more under treatments of the SynCom than the chemical fertilizer, while the fungal communities differed more under the chemical fertilizer treatment than the SynCom treatment. Regarding soil function, the SynCom strengthened the correlation between enzyme activities and both bacterial communities and functional properties. pH and available potassium were the main influencing factors under the chemical fertilizer and combined fertilizer treatments. The beta-diversity of the bacterial communities was significantly correlated with soil multifunctionality. Random forest analyses showed that the SynCom significantly enhanced the bacterial communities, driving soil multifunctionality, and that some potential microbial taxa drove multiple nutrient cycles simultaneously. In summary, the SynCom effectively increased the abundance of most carbon, nitrogen, and phosphorus functional genes as well as soil enzyme activities. The bacterial community composition contributed significantly to soil multifunctionality. Hence, the development of novel microbial agents holds significant potential for improving soil functionality and managing desertification.