Microbial community structures and functions of wastewater treatment systems in plateau and cold regions

Effect of iron-carbon microelectrolysis and magnetite on biological nitrogen removal: Analysis of microbial communities, functional genes, and mechanisms

Iron-carbon microelectrolysis (IC-ME) is a highly effective approach for achieving efficient denitrogenation in low carbon-to-nitrogen (C/N) ratio wastewater; however, its mechanism and electron transfer pathways remain unclear. This study developed iron-carbon fillers with added magnetite (Fe3O4) to investigate the influence of Fe3O4 and IC-ME on biological denitrification under varying C/N ratios. In batch experiments, the experimental group achieved an average total nitrogen removal improvement of 20.45% and 31.80%, respectively, compared to the control group at a simulated wastewater C/N ratio of 3. When compared to the sequencing batch reactor (SBR) without fillers, the SBR with iron-carbon fillers demonstrated a 22.50% increase in average total nitrogen removal. Additionally, activities of Cyt-c, complex I, and complex III significantly increased when the influent water C/N ratio was reduced to 3. The structural composition of the microbial community exhibited an abundance of denitrifying microorganisms, including Pseudomonadota, Betaproteobacteria, and Gammaproteobacteria, alongside iron-autotrophic denitrifying microorganisms such as Acidovorax and Pseudoxanthomonas. Moreover, the genes narG, nirS, and nosZ showed increased abundance, with most genes becoming progressively more abundant as the C/N ratio decreased. This study aims to provide valuable insights for energy conservation and carbon reduction in wastewater treatment plants facing limited carbon sources.

Impact of typhoon on nutrient contaminants, antibiotic resistance genes and microbial communities in mariculture tailwater treatment system

Intensive marine aquaculture generates complex pollutants, including nutrients and, threatening marine ecosystems. Biological treatments are effective but vulnerable to disruptions, especially during typhoons, which alter water quality and microbial communities. This study examined a mariculture tailwater (MTW) treatment system in Hainan over a year, focusing on seasonal performance in nutrient and ARGs removal, microbial community dynamics, impacts of environmental changes on functional microorganisms, and interactions of hosts of antibiotic resistance genes. The system effectively removed NH4+-N (63.74-94.73%) during non-typhoon seasons, but typhoons disrupted its nutrient pollutant reduction performance. The proportion of microorganisms involved in nitrogen and phosphorus removal decreased by changes of salinity in typhoon events. Antibiotic resistance genes relative abundances were enriched due to typhoon disaster. The majority antibiotic resistance genes in the system were associated with beta-lactam resistance (4.37 × 104-8.73 × 104). Rare bacterial taxa showed the strongest tolerance in all taxa to typhoon conditions. Archaeal community compositions were sensitive to these disturbances. Disperal limitation and heterogeneous selection were key drivers in bacterial and archaeal community assemblies. Microorganisms and antibiotic resistance genes often co-occurred in non-typhoon seasons. Vibrio was identified as a key potential host of antibiotic resistance genes in both seasons. This study highlights the disruptive effect of typhoons on the stability of MTW treatment systems.

Feasibility of coagulation-biological treatment of toxic herbal wastewater: Process performance, alkaloid removal and microbial characterization

Coagulation, anaerobic Expanded Granular Sludge Bed (EGSB) and Sequencing Batch Reactor (SBR), which are widely used in wastewater treatment, have important position in conventional wastewater treatment. However, these conventional processes have rarely been applied in special wastewater treatment such as toxic herbal wastewater. Can these conventional treatment processes be applied to the treatment of special wastewaters? In this study, coagulation-EGSB-SBR was used to treat a toxic herbal wastewater, and the change of microbial communities and the toxicity reduction in the process were analyzed. Under the optimal parameters, the removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and suspended substance (SS) by the combined process were 81.26 ± 1.60 %, 96.24 ± 0.76 %, and 97.13 ± 1.26 %. The removal of aconitine, hypaconitine, mesaconitine, and benzoylmesaconine were 80.94 ± 26.96 %, 100.00 ± 0.00 %, and 89.12 ± 0.89 %. During the domestication of sludge, the microorganisms inside the SBR gradually changed from Flavobacterium to Propioniciclava and Niabella, which degraded some refractory organics. In the EGSB, the dominant bacteria changed from Propioniciclava to Bacteroides. The results of this study demonstrated that the combined process effectively removed organic pollutants and alkaloids from the wastewater.

Achieving endogenous partial denitrification by cultivating denitrifying glycogen-accumulating organisms

Although anaerobic ammonia oxidation (anammox) is considered a promising process due to its high efficiency and low energy in nitrogen removal, nitrite inadequacy was one of the bottlenecks for the application of anammox. However, endogenous partial denitrification (EPD) has been emerging as a stable pathway to provide nitrite for anammox. Furthermore, denitrifying glycogen-accumulating organisms (DGAOs) are believed to be associated with EPD. In this study, firstly, GAOs were gradually enriched in a sequencing batch reactor (SBR) with the dual strategy of influent phosphorus limitation and withdrawal after the anaerobic stage. DGAOs were successfully induced by adding sodium nitrate solution at the end of the anaerobic stage, resulting in NO3--N concentration increasing from 15 to 30 mg/L. During a typical SBR cycle, DGAOs contributed up to 96% of the conversion of intracellular carbon sources and up to around 95% of nitrate reduction during the anoxic stage. The maximum nitrate-to-nitrite transformation ratio (NTR) of the system reached 80%. Microbial community analysis demonstrated that the Ca. Compatibactors were the dominant functional bacteria for EPD, with a relative abundance of 31.12%. However, the relative abundance of phosphorous-accumulating organisms (PAOs) was only 1.02%. This study reveals the important role of DGAOs in the EPD process, which can provide a stable nitrite for anammox.

Potential postmortem microbial biomarkers of infant and younger children death investigation

Microbial communities associated with the human body are highly dynamic and reflect the host environment and lifestyle over time. Studies show death is no exception, with data demonstrating similar antemortem and postmortem microbiomes up to 48 h following death. These predictable microbial biomarkers can inform death investigation by helping to estimate the postmortem interval and build models to identify cause and manner of death. However, no attempts have been made to model potential microbial biomarkers in pediatric (≤2 years) deaths. This study provided a cross-sectional survey of the microbiota of 53 pediatric cases (black, white, both sexes) seen in Wayne County, Michigan. Autopsy cases represented accidents, homicides, or natural causes. Postmortem microbiome were collected by swabbing the eyes, ears, nose, mouth, umbilicus, brain, rectum, trabecular space, and cardiac blood. 16S rRNA sequence analyses indicated that sex, race, age, body site, and manner of death (MOD) had significant effects on microbiome composition, with significant interactions among MOD, race, and age. Amplicon sequence variants identified intra- and interhost dispersion of the postmortem microbiome depending on death circumstance. Among manners of death, non-accidental deaths were significantly distinct from all other deaths, and among body sites the rectum was distinct in its microbial composition. There is a real need for robust postmortem microbiome before it can be standardized as a practical tool for use in forensic investigation or public health. These results inform postmortem microbial variability during pediatric death investigation that contributes to a larger effort to understand the postmortem microbiome.

Integrating Microalgal Chlorella Biomass and Biorefinery Residues into Sustainable Agriculture and Food Production: Insights from Lettuce Cultivation

Microalgal biomass offers a promising biofertilizer option due to its nutrient-rich composition, adaptability, and environmental benefits. This study evaluated the potential of microalgal-based biofertilizers-microalgal Chlorella biomass, de-oiled microalgal biomass (DMB), and de-oiled and de-aqueous extract microalgal biomass (DAEMB)-in enhancing lettuce growth, soil nutrient dynamics, and microbial community composition. Lettuce seedlings were cultivated with these biofertilizers, and plant growth parameters, photosynthetic pigments, and nitrogen uptake were assessed. Soil incubation experiments further examined nutrient mineralization rates, while DNA sequencing analyzed shifts in rhizosphere microbial communities. Lettuce grown with these biofertilizers exhibited improved growth parameters compared to controls, with Chlorella biomass achieving a 31.89% increase in shoot length, 27.98% in root length, and a 47.33% increase in fresh weight. Chlorophyll a and total chlorophyll levels increased significantly in all treatments, with the highest concentrations observed in the Chlorella biomass treatment. Soil mineralization studies revealed that DMB and DAEMB provided a gradual nitrogen release, while Chlorella biomass exhibited a rapid nutrient supply. Microbial community analyses revealed shifts in bacterial and fungal diversity, with increased abundance of nitrogen-fixing and nutrient-cycling taxa. Notably, fungal diversity was enriched in biomass and DAEMB treatments, enhancing soil health and reducing pathogenic fungi. These findings highlight microalgal biofertilizers' potential to enhance soil fertility, plant health, and sustainable resource use in agriculture.

Proteomic and spectral analysis reveals the role of extracellular polymeric substances in mercury biosorption by activated sludge under high-altitude conditions

In high-altitude regions, elevated mercury (Hg) levels in wastewater treatment plants (WWTPs) influent raise concerns about treatment efficiency and environmental impact. This study investigated the Hg biosorption capacity of activated sludge under high-altitude conditions, focusing on the binding mechanisms between EPS and Hg, and variations in EPS secretion. Low pressure, oxygen, and temperature at high altitudes increase EPS secretion, enhancing Hg biosorption. EPS provides numerous binding sites for Hg, forming nonfluorescent complexes with tryptophan-like and aromatic proteins, while hydrocarbon and oxygen-containing groups limit Hg entry into microbial cells. Proteomic analysis revealed the upregulation of transporters, stress-resistance, and binding proteins, along with those involved in carbon and amino acid metabolism, which enhance microbial resilience and EPS production, leading to increased Hg biosorption. These insights reveal adaptive mechanisms that optimize pollutant removal in high-altitude environments.

Biodegradation-assisted removal of sulfur-based odor compounds in rural drinking water using durable chitosan/polyvinyl alcohol biochar aerogels

Rural drinking water often suffers from unpleasant odors like dimethyl sulfide (DMDS) and dimethyl trisulfide (DMTS) due to poor raw water quality and limited treatment options. This study introduces durable chitosan/polyvinyl alcohol (PVA) biochar aerogels-supported bioflims in ultrafiltration (BAB-UF) reactors, where the incorporation of PVA significantly enhances structural integrity, biodegradation resistance, and functional lifespan, providing an efficient, sustainable solution for removing odorous compounds from rural water. Experimental results showed the enhanced chitosan/PVA porous biochar aerogels (CPPCA) displayed excellent biocapacity and structural stability. After 63 days of continuous operation, the degradation rate of biochar aerogels with 0.2 wt% PVA (CP2PCA) was only 8.2 %. The one-step membrane reactors utilizing PVA-enhanced aerogels achieved removal efficiencies for DMDS/DMTS pollutants of up to 98.4 %, surpassing systems without PVA. These findings indicate the potential for improved aerogels in rural drinking water treatment, providing a viable solution for effective and low-maintenance water purification.

Enhancement of aerobic sludge granulation by quorum sensing signaling molecules mediated by biomimetic bacterial extracellular vesicles

The addition of exogenous quorum sensing signaling molecules to the activated sludge system enables rapid sludge granulation. However, signaling molecules exposed to the environment are easily degraded, and their quorum sensing effects cannot be maintained in the long term. Therefore, they must be frequently added, which leads to an increase in operational costs. In this study, signaling molecules, acylated homoserine lactones (AHLs), were packaged into biomimetic bacterial extracellular vesicles-lipid vesicles (AHLs@ZZT), and the mediating role of lipid vesicles for AHLs was utilized to improve the utilization efficiency of signaling molecules. The results show that packaging of AHLs into vesicles slowed down the release of AHLs and protected them from degradation by porcine renal acylase. Moreover, the chemical properties of lipid vesicles are similar to the structure of bacterial cell walls, making it easier for the packaged AHLs to bind to target bacteria, thereby generating more EPS and accelerating the aggregation of microorganisms. After adding the lipid vesicles loaded with AHLs into the activated sludge system, the sludge granulation process was accelerated. Furthermore, the frequency of AHLs@ZZT addition was reduced by three times compared to that of unpackaged AHLs, resulting in a granular sludge with a smoother and denser surface. High-throughput sequencing of the sludge genome in the system indicated that adding AHLs@ZZT could promote microbial diversity and enrich functional microorganisms. Three-dimensional fluorescence spectra further revealed that the tryptophan and tyrosine proteins in extracellular polymeric substances secreted by these microorganisms facilitated sludge granulation. In summary, the lipid vesicle-mediated signaling molecular strategy can promote the rapid formation of granular sludge and maintain the long-term stability of the granular sludge structure, representing an economic and feasible regulation strategy.

Characteristics of the Bacterial Community in Alpine Meadows in Response to Altitude and Aspect in the Qilian Mountains, Northwest China

As one of the most sensitive and fragile alpine ecosystems in the Qilian Mountains, the alpine meadow holds significant scientific importance in understanding the changes in the characteristics of soil bacterial community in response to altitude and aspect variations. In our study, we analyzed the composition, diversity, and function of soil bacterial communities in alpine meadows at different altitudes and aspects and their relationship with environmental factors. Our results indicate that altitude and aspect orientation significantly influences the diversity index and composition of soil bacterial communities. Specifically, the Shannon and Chao1 indices of soil bacteria initially increased and then decreased with increasing altitude, with the Shannon index being lower in shady aspects compared to sunny aspects, and the Chao1 index being lower in sunny aspects above an altitude of 3400 m compared to shady aspects at the exact altitudes. Using Linear Discriminant Analysis Effect Size analysis, we identified 77 bacterial species in the research area, with key ecological functions primarily associated with nitrification, aerobic ammonia oxidation, and chitinolysis. Furthermore, we found that soil water content and Urease were the main factors influencing bacterial community composition. Our findings underscore the significant impact of altitude orientation on bacterial communities in alpine grasslands, emphasizing the importance of considering bacterial differences in evaluating alpine grassland health.

The life strategy of bacteria rather than fungi shifts in karst tiankeng island-like systems

Karst tiankeng is a typical terrestrial habitat island-like system, known as an oasis in a degraded karst landscape. However, we know little about the composition, structure, and life strategies of soil microbial communities in the karst tiankeng ecosystem. In this study, we use amplicon sequencing to investigate the soil bacteria and fungi of 26 karst tiankeng in two typical karst tiankeng groups. The results showed that the composition and structure of bacterial and fungal communities were significantly different at two dimensions (among and within the karst tiankeng group). Bacteria showed more sensitivity to variation in the karst tiankeng area and isolation than fungi. With the increase of karst tiankeng area and isolation, the bacterial life strategies shift from K-strategist to r-strategist, likely due to the changes in soil properties (total phosphorus, Ca, and soil water content). Abundant and rare taxa play different roles in karst tiankeng ecosystems; abundant taxa serve a key role in nutrient cycles and life strategy shifts by occupying the key status in networks. Considering the key role of soil microbes in ecosystems, more attention must be paid to the impact of habitat loss on soil microbial life strategies, particularly in the ecological impact of life strategies change of abundant and rare taxa.

IMPORTANCE

These findings highlight that habitat loss or fragmentation induces a shift in microbial life strategies and improves our understanding of the composition and biogeography of karst ecosystem microorganisms.

Changes in microbial communities across the whole A2/O wastewater treatment process and their drivers-Reduced community diversity but increased proportion of certain pathogens

Microorganisms play a crucial role in pollutant removal and water quality stabilizing. However, limited research exists on the microbial variability and the factors driving it at different stages of wastewater treatment. In this study, the physicochemical properties of water and the composition of bacterial communities were thoroughly investigated across the entire A2/O wastewater treatment process, encompassing 3 stages (12 steps). The results revealed a significant reduction in alpha diversity, whereas the beta diversity remained largely unchanged across stages. Alpha diversity was primarily influenced by dissolved oxygen (DO) and pH, with DO having the most notable influence, while beta diversity was mainly constrained by nutrient conditions such as COD, BOD5, NH4-N, TN, and TP. Additionally, analyses of relative abundance, LEfSe, variance, and functional prediction indicated a significant increase in the relative abundance of certain pathogenic bacteria (e.g., Legionella, Leptospira), exhibiting different removal characteristics compared to Escherichia coli across various treatment steps. Even after UV disinfection, these pathogens persist, highlighting a potential pathogenic risk, which deserves more attention. In addition, this study helps explore the relatively under-researched area of microbial variability at different stages (steps) of wastewater treatment, especially in terms of how microbial communities respond to operational processes and environmental conditions. This will offer valuable guidance for addressing water treatment safety challenges encountered in real-world processes.

Effect of magnetic powder (Fe3O4) on heterotrophic-sulfur autotrophic denitrification efficiency and electron transport system activity for marine recirculating aquacultural wastewater treatment

As an efficient nitrogen removal process, heterotrophic-sulfur autotrophic denitrification (HSAD) has attracted extensive attention in wastewater treatment. However, the effects of magnetic powder (Fe3O4) on the electron transport activity in HSAD process remain unclear. Therefore, in this study, a heterotrophic-sulfur autotrophic denitrification system was established to remove nitrogen from marine recirculating aquacultural wastewater for evaluating the effects of Fe3O4. At the optimal Fe3O4 concentration of 50 mg/L, the nitrogen removal efficiency reached 100% with lower sulfate accumulation, and the start-up time was shortened. The assays of denitrifying enzymes and electron transport system activity showed that Fe3O4 improved the activities of nitrate and nitrite reductases, and increased the efficiency of electron transport. Microbial community analysis revealed that Fe3O4 enriched heterotrophic denitrifier Thauera and sulfur autotrophic denitrifier Canditatus Thiobios, and thus enhanced denitrification efficiencies. This study demonstrated that Fe3O4 is an efficient denitrification accelerator in HSAD for treating marine recirculating aquacultural wastewater.

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 (NH4+-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 min, 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.

Unravelling the microbiome of wild flowering plants: a comparative study of leaves and flowers in alpine ecosystems

BACKGROUND

While substantial research has explored rhizosphere and phyllosphere microbiomes, knowledge on flower microbiome, particularly in wild plants remains limited. This study explores into the diversity, abundance, and composition of bacterial and fungal communities on leaves and flowers of wild flowering plants in their natural alpine habitat, considering the influence of environmental factors.

METHODS

We investigated 50 wild flowering plants representing 22 families across seven locations in Austria. Sampling sites encompassed varied soil types (carbonate/silicate) and altitudes (450-2760 m). Amplicon sequencing to characterize bacterial and fungal communities and quantitative PCR to assess microbial abundance was applied, and the influence of biotic and abiotic factors assessed.

RESULTS

Our study revealed distinct bacterial and fungal communities on leaves and flowers, with higher diversity and richness on leaves (228 fungal and 91 bacterial ASVs) than on flowers (163 fungal and 55 bacterial ASVs). In addition, Gammaproteobacteria on flowers and Alphaproteobacteria on leaves suggests niche specialization for plant compartments. Location significantly shaped both community composition and fungal diversity on both plant parts. Notably, soil type influenced community composition but not diversity. Altitude was associated with increased fungal species diversity on leaves and flowers. Furthermore, significant effects of plant family identity emerged within a subset of seven families, impacting bacterial and fungal abundance, fungal Shannon diversity, and bacterial species richness, particularly on flowers.

CONCLUSION

This study provides novel insights into the specific microbiome of wild flowering plants, highlighting adaptations to local environments and plant-microbe coevolution. The observed specificity indicates a potential role in plant health and resilience, which is crucial for predicting how microbiomes respond to changing environments, ultimately aiding in the conservation of natural ecosystems facing climate change pressures.

What is the Difference between Conventional Drinking Water, Potable Reuse Water, and Nonpotable Reuse Water? A Microbiome Perspective

As water reuse applications expand, there is a need for more comprehensive means to assess water quality. Microbiome analysis could provide the ability to supplement fecal indicators and pathogen profiling toward defining a "healthy" drinking water microbiota while also providing insight into the impact of treatment and distribution. Here, we utilized 16S rRNA gene amplicon sequencing to identify signature features in the composition of microbiota across a wide spectrum of water types (potable conventional, potable reuse, and nonpotable reuse). A clear distinction was found in the composition of microbiota as a function of intended water use (e.g., potable vs nonpotable) across a very broad range of U.S. water systems at both the point of compliance (Betadisper p > 0.01; ANOSIM p < 0.01, r-stat = 0.71) and point of use (Betadisper p > 0.01; ANOSIM p < 0.01, r-stat = 0.41). Core and discriminatory analysis further served in identifying distinct differences between potable and nonpotable water microbiomes. Taxa were identified at both the phylum (Desulfobacterota, Patescibacteria, and Myxococcota) and genus (Aeromonas and NS11.12_marine_group) levels that effectively discriminated between potable and nonpotable waters, with the most discriminatory taxa being core/abundant in nonpotable waters (with few exceptions, such as Ralstonia being abundant in potable conventional waters). The approach and findings open the door to the possibility of microbial community signature profiling as a water quality monitoring approach for assessing efficacy of treatments and suitability of water for intended use/reuse application.

Variations in soil microbial communities in different saline soils under typical Populus spp. vegetation in alpine region of the Qaidam Basin, NW China

Salinization is a severe threat to agriculture and the environment in many areas, and the same in Qaidam Basin, Qinghai Province, Northwestern China. Microorganisms have an important influence on regulating the biochemical cycles of ecosystems; however, systematic research exploring microbial diversity and interactions with saline-soil ecosystems' environmental variables remains scarce. Thus, 16 S rRNA high-throughput sequencing was performed in this paper to characterize microbial diversity under different levels of salinized soils: non-salinized (NS, 2.25 g/L), moderately salinized (MS, 6.14 g/L) and highly salinized (HS, 9.82 g/L). The alpha diversity results showed that the HS soil was significantly different from the NS and MS soils. An analysis of similarity (ANOSIM) and a principal co-ordinates analysis (PCoA) indicated that NS and MS clustered closely while HS separated from the other two. Significant differences in microbial composition were observed at the taxonomic level. Proteobacteria (42.29-79.23 %) were the most abundant phyla in the studied soils. Gammaproteobacteria (52.49 and 66.61 %) had higher abundance in the MS and HS soils at the class level; Methylophaga and Pseudomonas were the predominant bacteria in the HS soil; and Azotobacter and Methylobacillus were abundant in the MS soil. Most genera belonging to Proteobacteria and Actinobacteria were detected via a linear discriminate analysis (LDA) effect size (LEfSe) analysis, which indicated that microbes with the ability to degrade organic matter and accomplish nutrient cycling can be well-adapted to salt conditions. Further analyses (redundancy analysis and Mantel test) showed that the microbial communities were mainly related to the soil salinity, electrical conductivity (EC1:5), total phosphorus (TP) and ammonia nitrogen (NH4+-N). Overall, the findings of the study can provide insights for better understanding the dominant indigenous microbes and their roles in biochemical cycles in different saline soils in the Qaidam Basin, Qinghai Province, China. The researches related to microbial community under typical poplar species should further clarify the mechanism of plant-microbial interaction and benefit for microbial utilization in salt soil remediation.

Synergistic reduction of pollution and carbon mitigation in constructed wetlands-microbial fuel cell using sludge-derived biochar

Integrating microbial fuel cells (MFC) into constructed wetland systems (CW) has been an efficient wastewater treatment to improve the pollutants removal and regenerate power energy. This study fabricated a sludge biochar material (SBM) to sequestrate the carbon of residual sludge. Thereafter used SBM and modified SBM as the substrate materials to construct three groups of CW-MFC for decreasing the greenhouse gas (GHG) emission. The water quality improvement in removal efficiency achieved (2.59 %, 3.10 %, 5.21 % for COD; 3.31 %, 3.60 %, 6.71 % for TN; 1.80 %, 7.38 %, 4.93 % for TP) by the application of MFC, SBM, and modified SBM in wastewater treatment, respectively. Additionally, the reduction in global warming potential (GWP) realized 17.2 %, 42.2 %, and 64.4 % resulting from these applications. The carbon flow and fate diagrams showed MFC shifted the gas phase‑carbon flow from CH4 to CO2, and SBM promoted this shift trends. Microbial diversity indicated enrichment of electrochemically active bacteria (EAB), denitrifying bacteria, and phosphate accumulating organisms (PAOs) by SBM. Metabolic pathways analysis showed that introduction of MFC and SBM exhibited significant increases of key functional genes in metabolic pathway of anaerobic oxidation of methane (AOM). This study highlights the benefit of CW-MFC in and provides a new strategy for removing pollutants and abating GHG emissions in wastewater treatment.

Macrogenomics Reveals Effects on Marine Microbial Communities during Oplegnathus punctatus Enclosure Farming

(1) Background: Laizhou Bay is an important aquaculture area in the north of China. Oplegnathus punctatus is one of the species with high economic benefits. In recent years, the water environment of Laizhou Bay has reached a mild eutrophication level, while microorganisms are an important group between the environment and species. In this study, we evaluated alterations in environmental elements, microbial populations, and antibiotic resistance genes (ARGs) along with their interconnections during Oplegnathus punctatus net culture. (2) Methods: A total of 142 samples from various water layers were gathered for metagenome assembly analysis. Mariculture increases the abundance of microorganisms in this culture area and makes the microbial community structure more complex. The change had more significant effects on sediment than on seawater. (3) Results: Certain populations of cyanobacteria and Candidatus Micrarchaecta in seawater, and Actinobacteria and Thaumarchaeota in sediments showed high abundance in the mariculture area. Antibiotic resistance genes in sediments were more sensitive to various environmental factors, especially oxygen solubility and salinity. (4) Conclusions: These findings highlight the complex and dynamic nature of microorganism-environment-ARG interactions, characterized by regional specificity and providing insights for a more rational use of marine resources.

Effect of tire wear particle accumulation on nitrogen removal and greenhouse gases abatement in bioretention systems: Soil characteristics, microbial community, and functional genes

Tire wear particles (TWPs), as predominant microplastics (MPs) in road runoff, can be captured and retained by bioretention systems (BRS). This study aimed to investigate the effect of TWPs accumulation on nitrogen processes, focusing on soil characteristics, microbial community, and functional genes. Two groups of lab-scale bioretention columns containing TWPs (0 and 100 mg g-1) were established. The removal efficiencies of NH4+-N and TN in BRS significantly decreased by 7.60%-24.79% and 1.98%-11.09%, respectively, during the 101 days of TWPs exposure. Interestingly, the emission fluxes of N2O and CO2 were significantly decreased, while the emission flux of CH4 was substantially increased. Furthermore, prolonged TWPs exposure significantly influenced the contents of soil organic matter (increased by 27.07%) and NH4+-N (decreased by 42.15%) in the planting layer. TWPs exposure also significantly increased dehydrogenase activity and substrate-induced respiration rate, thereby promoting microbial metabolism. Microbial sequencing results revealed that TWPs decreased the relative abundance of nitrifying bacteria (Nitrospira and Nitrosomonas) and denitrifying bacteria (Dechloromonas and Thauera), reducing the nitrification rate by 42.24%. PICRUSt2 analysis further indicated that TWPs changed the relative abundance of functional genes related to nitrogen and enzyme-coding genes.

Recovery of nutrients from fish sludge to enhance the growth of microalga Chlorella sorokiniana CMBB276

Intensive aquaculture production generates large amounts of sludge. This waste could be considered as a potential source of nutrients that can be recovered and utilized. Little attention has been paid to nutrient recovery from fish sludge. In this study, bioconversion of sludge was evaluated in lab scale under anaerobic (AN), facultative anaerobic (FA) and aerobic (AE) conditions. After 40 days of fermentation, AN recovered the highest values of dissolved total nitrogen (82.7 mg L-1), while AE showed the highest dissolved total phosphorus (11.8 mg L-1) and the highest reduction of total suspended solids (36.0 %). Microbial analysis showed that AN exhibited a distinct bacterial community than that of FA and AE. Furthermore, C. sorokiniana grown in AN effluents collected after 12 days of fermentation achieved the highest biomass production (1.96 g L-1). These results suggest that AN has the best potential to recover nutrients from sludge for production of C. sorokiniana.

Impacts of cadmium accumulation on the diversity, assembly processes, and co-occurrence patterns of archaeal communities in marine sediments

There is limited understanding regarding the changes in the ecological processes and the mechanisms of archaeal community in response to heavy metal contamination in the marine sediments. In this study, sediment samples were collected from 46 locations near harbors, and the concentration of heavy metals and the diversity of archaeal communities were investigated to understand the impact of Cd on archaeal communities. The results demonstrated a significant correlation between the diversity of archaeal community and Cd concentration, particularly showing a linear decrease in the species richness with rising Cd concentration. ANME-1b was identified as a significantly enriched archaeal taxon in the higher Cd environment. Null model and neutral community model indicated that the ecological assembly of archaeal communities in marine sediments was primarily governed by the stochastic processes, with dispersal limitation being the primary factor. The contribution of deterministic process to the assembly of archaeal communities in higher Cd environments increased clearly, accompanied by a notable reduction in species migration rates and widths of ecological niche of archaeal populations. Co-occurrence network analysis revealed an obvious increase in species interactions in higher Cd environments, with an apparent rise in the proportion of competitive relationships and an increase in the number of keystone species. Moreover, archaeal species formed a more complex and stable community to cope with Cd stress. This study provides new insights into the impacts of heavy metals on the ecological processes of marine microorganisms and the underlying mechanisms.

Response of aerobic granular sludge under acute inhibition by polystyrene microplastics: Activity, aggregation performance, and microbial analysis

In this study, the activity, aggregation performance, microbial community and functional proteins of aerobic granular sludge (AGS) in response to acute inhibition by different concentrations of polystyrene microplastics (PS-MPs) were investigated. As the PS-MPs concentration increased from 0 mg/L to 200 mg/L, the specific nitrogen removal rate and the activity of enzymes were inhibited. The inhibition of specific nitrite reduction rate (SNIRR) and specific nitrate reduction rate (SNRR) was most obvious at the PS-MPs concentration of 100 mg/L, and that of nitrite reductase (NIR) and nitrate reductase (NR) was most obvious at the concentration of 50 mg/L. But the inhibitory effects were mitigated at the concentration of 200 mg/L. The increase of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) indicated that the cells were damaged with the increase of PS-MPs concentration. The content of proteins and polysaccharides in extracellular polymeric substances (EPS) decreased, especially the polysaccharides were more affected. Analysis of zeta potential, hydrophobicity and surface thermodynamics of AGS revealed that addition of PS-MPs was unfavorable for AGS aggregation. It was also found that bacteria genera associated with EPS secretion and nitrogen removal functions were inhibited, while functions associated with cell metabolism, protein synthesis and cell repair were enhanced. This also confirmed that acute inhibition of PS-MPs had a detrimental effect on the nitrogen removal and aggregation performance of AGS. This study can provide theoretical support for the operation of AGS reactors under microplastics impact load.

Bacterial community structure analysis of sludge from Taozi lake and isolation of an efficient 17β-Estradiol (E2) degrading strain Sphingobacterium sp. GEMB-CSS-01

Environmental challenges arising from organic pollutants pose a significant problem for modern societies. Efficient microbial resources for the degradation of these pollutants are highly valuable. In this study, the bacterial community structure of sludge samples from Taozi Lake (polluted by urban sewage) was studied using 16S rRNA sequencing. The bacterial phyla Proteobacteria, Bacteroidetes, and Chloroflexi, which are potentially important in organic matter degradation by previous studies, were identified as the predominant phyla in our samples, with relative abundances of 48.5%, 8.3%, and 6.6%, respectively. Additionally, the FAPROTAX and co-occurrence network analysis suggested that the core microbial populations in the samples may be closely associated with organic matter metabolism. Subsequently, sludge samples from Taozi Lake were subjected to enrichment cultivation to isolate organic pollutant-degrading microorganisms. The strain Sphingobacterium sp. GEMB-CSS-01, tolerant to sulfanilamide, was successfully isolated. Subsequent investigations demonstrated that Sphingobacterium sp. GEMB-CSS-01 efficiently degraded the endocrine-disrupting compound 17β-Estradiol (E2). It achieved degradation efficiencies of 80.0% and 53.5% for E2 concentrations of 10 mg/L and 20 mg/L, respectively, within 10 days. Notably, despite a reduction in degradation efficiency, Sphingobacterium sp. GEMB-CSS-01 retained its ability to degrade E2 even in the presence of sulfanilamide concentrations ranging from 50 to 200 mg/L. The findings of this research identify potential microbial resources for environmental bioremediation, and concurrently provide valuable information about the microbial community structure and patterns within Taozi Lake.

Metabolomic insight into regulatory mechanism of heterotrophic bacteria nitrification-aerobic denitrification bacteria to high-strength ammonium wastewater treatment

This work aimed to elucidate the metabolic mechanism of heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria influenced by varying concentrations of ammonium nitrogen (NH4+-N) in high-strength synthetic wastewater treatment. The results showed that the removal rates of NH4+-N and total nitrogen, along with enzymatic activities related to nitrification and denitrification, increased with rising NH4+-N concentrations (N500:500 mg/L, N1000:1000 mg/L and N2000:2000 mg/L). The relative abundances of HN-AD bacteria were 50 %, 62 % and 82 % in the three groups. In the N2000 group, the cAMP signaling pathway, glycerophospholipid metabolites, purines and pyrimidines related to DNA/RNA synthesis, electron donor NAD+-related energy, the tricarboxylic acid (TCA) cycle and glutamate metabolism were upregulated. Therefore, influent NH4+-N at 2000 mg/L promoted glutamate metabolism to accelerate the TCA cycle, and enhanced cellular energy and advanced denitrification activity of bacteria for HN-AD. This mechanism, in turn, enhanced microbial growth and the carbon and nitrogen metabolism of bacteria for HN-AD.

Deciphering the Role of WWTPs in Cold Environments as Hotspots for the Dissemination of Antibiotic Resistance Genes

Cold environments are the most widespread extreme habitats in the world. However, the role of wastewater treatment plants (WWTPs) in the cryosphere as hotspots in antibiotic resistance dissemination has not been well established. Hence, a snapshot of the resistomes of WWTPs in cold environments, below 5 °C, was provided to elucidate their role in disseminating antibiotic resistance genes (ARGs) to the receiving waterbodies. The resistomes of two natural environments from the cold biosphere were also determined. Quantitative PCR analysis of the aadA, aadB, ampC, blaSHV, blaTEM, dfrA1, ermB, fosA, mecA, qnrS, and tetA(A) genes indicated strong prevalences of these genetic determinants in the selected environments, except for the mecA gene, which was not found in any of the samples. Notably, high abundances of the aadA, ermB, and tetA(A) genes were found in the influents and activated sludge, highlighting that WWTPs of the cryosphere are critical hotspots for disseminating ARGs, potentially worsening the resistance of bacteria to some of the most commonly prescribed antibiotics. Besides, the samples from non-disturbed cold environments had large quantities of ARGs, although their ARG profiles were highly dissimilar. Hence, the high prevalences of ARGs lend support to the fact that antibiotic resistance is a common issue worldwide, including environmentally fragile cold ecosystems.

Linking the shifts in the metabolically active microbiota in a UASB and hybrid anaerobic-aerobic bioreactor for swine wastewater treatment

Due to the high concentration of pollutants, swine wastewater needs to be treated prior to disposal. The combination of anaerobic and aerobic technologies in one hybrid system allows to obtain higher removal efficiencies compared to those achieved via conventional biological treatment, and the performance of a hybrid system depends on the microbial community in the bioreactor. Here, we evaluated the community assembly of an anaerobic-aerobic hybrid reactor for swine wastewater treatment. Sequencing of partial 16S rRNA coding genes was performed using Illumina from DNA and retrotranscribed RNA templates (cDNA) extracted from samples from both sections of the hybrid system and from a UASB bioreactor fed with the same swine wastewater influent. Proteobacteria and Firmicutes were the dominant phyla and play a key role in anaerobic fermentation, followed by Methanosaeta and Methanobacterium. Several differences were found in the relative abundances of some genera between the DNA and cDNA samples, indicating an increase in the diversity of the metabolically active community, highlighting Chlorobaculum, Cladimonas, Turicibacter and Clostridium senso stricto. Nitrifying bacteria were more abundant in the hybrid bioreactor. Beta diversity analysis revealed that the microbial community structure significantly differed among the samples (p < 0.05) and between both anaerobic treatments. The main predicted metabolic pathways were the biosynthesis of amino acids and the formation of antibiotics. Also, the metabolism of C5-branched dibasic acid, Vit B5 and CoA, exhibited an important relationship with the main nitrogen-removing microorganisms. The anaerobic-aerobic hybrid bioreactor showed a higher ammonia removal rate compared to the conventional UASB system. However, further research and adjustments are needed to completely remove nitrogen from wastewater.

Funneliformis mosseae influences leaf decomposition by altering microbial communities under saline-alkali conditions

Recent studies have indicated that arbuscular mycorrhizal fungi (AMF) can influence decomposition of organic materials. However, the underlying mechanisms remain unclear. Here we investigated whether AMF influence the decomposition of leaf litters and change the associated litter bacterial and fungal communities and whether this effect is altered by the level of soil saline-alkali. A pot experiment was conducted using Trifolium repens as host plant without or with AMF (Funneliformis mosseae) and with two levels of soil saline-alkali (0 and 200 mmol/L). Litterbags with different mesh size were used to measure the effect of AMF on decomposition. Our study found that AMF significantly accelerated leaf litter decomposition under both non-saline-alkali and saline-alkali conditions. The composition of bacterial and fungal communities was also altered by AMF independent of soil saline-alkali conditions. For bacterial community, AMF increased the richness but not the diversity and increased the relative abundance of Firmicutes and Nitrospirota. For fungal community, the richness and diversity were higher in AMF than in non-AMF treatment. AMF significantly resulted in a decrease of the relative abundance of Ascomycota but an increase of the relative abundance of Basidiomycota, Chytridiomycota, Mortierellomycota and Rozellomycota. Structural equation modeling (SEM) showed that AMF increased leaf litter decomposition under saline-alkali conditions primarily by affecting bacterial community composition. Together, we show that AMF increase decomposition and alter the bacterial and fungal communities, and that these effects are not modulated by the level of soil saline-alkali.

Effect of plant-self debris on nitrogen removal, transformation and microbial community in mesocosm constructed wetlands planted with Myriophyllum aquaticum

Aquatic macrophytes debris decomposition could release pollutants and nutrients into the water of constructed wetlands (CWs), but their role in nitrogen removal and transformation remains poorly understood. The present study investigated the effects of plant-self debris on nitrogen removal and microbial communities in mesocosm CWs planted with Myriophyllum aquaticum. During the 68-day operation, the plant debris addition did not change the mean removal efficiency of ammonium (NH₄⁺-N) and total nitrogen (TN) of CWs but showed significant differences over the operation time. The NH₄⁺-N and organic nitrogen released from the plant debris decomposition affected the nitrogen removal. The plant debris decreased the effluent nitrate concentration and N₂O emission fluxes of the CWs with the increased abundance of denitrifying bacterial genera, indicating that plant debris decomposition increased the denitrification activities via dissolved organic carbon release. High-throughput sequencing indicated that the plant debris altered the distribution and composition of the microbial community in the sediments. Proteobacteria was the dominant phylum (28-52%), and the relative abundance of denitrifying bacteria genera was significantly higher in the sediments with debris addition (37-40%) than in the non-addition (6.6-7.7%). The present study provided new insights into the role of macrophytes in pollutant removal and the plant management strategy of CWs.

Investigation of underlying links between nitrogen transformation and microorganisms' network modularity in the novel static aerobic composting of dairy manure by "stepwise verification interaction analysis"

Conventional composting is a viable method treating agricultural solid waste, and microorganisms and nitrogen transformation are the two major components of this proces. Unfortunately, conventional composting is time-consuming and laborious, and limited efforts have been made to mitigate these problems. Herein, a novel static aerobic composting technology (NSACT) was developed and employed for the composting of cow manure and rice straw mixtures. During the composting process, physicochemical parameters were analyzed to evaluate the quality of compost products, and microbial abundance dynamics were determined using high-throughput sequencing technique. The results showed that NSACT achieved compost maturity within 17 days as the thermophilic stage (≥55 °C) lasted for 11 days. GI, pH, and C/N were 98.71 %, 8.38, and 19.67 in the top layer, 92.32 %, 8.24, and 22.38 in the middle layer, 102.08 %, 8.33, and 19.95 in the bottom layer. These observations indicate compost products maturated and met the requirements of current legislation. Compared with fungi, bacterial communities dominated NSACT composting system. Based on the stepwise verification interaction analysis (SVIA), the novel combination utilization of multiple statistical analyses (Spearman, RDA/CCA, Network modularity, and Path analyses), bacterial genera Norank Anaerolineaceae (-0.9279*), norank Gemmatimonadetes (1.1959*), norank Acidobacteria (0.6137**) and unclassified Proteobacteria (-0.7998*), and fungi genera Myriococcum thermophilum (-0.0445), unclassified Sordariales (-0.0828*), unclassified Lasiosphaeriaceae (-0.4174**), and Coprinopsis calospora (-0.3453*) were the identified key microbial taxa affecting NH4+-N, NO3--N, TKN and C/N transformation in the NSACT composting matrix respectively. This work revealed that NSACT successfully managed cow manure-rice straw wastes and significantly shorten the composting period. Interestingly, most microorganisms observed in this composting matrix acted in a synergistic manner, promoting nitrogen transformation.

Bio-clogging mitigation in constructed wetland using microbial fuel cells with novel hybrid air-photocathode

Excessive accumulation of extracellular polymeric substances (EPS) in constructed wetland (CW) substrate can lead to bio-clogging and affect the long-term stable operation of CW. In this study, a microbial fuel cell (MFC) was coupled with air-photocathode to mitigate CW bio-clogging by enhancing the micro-electric field environment. Because TiO₂/biochar could catalyze and accelerate oxygen reduction reaction, further promoting the gain of electric energy, the electricity generation of the tandem CW-photocatalytic fuel cell (CW-PFC) reached 90.78 mW m^-3. After bio-clogging was mitigated in situ in tandem CW-PFC, the porosity of CW could be restored to about 62.5 % of the initial porosity, and the zeta potential of EPS showed an obvious increase (-14.98 mV). The removal efficiencies of NH₄⁺-N and chemical oxygen demand (COD) in tandem CW-PFC were respectively 31.8 ± 7.2 % and 86.1 ± 6.8 %, higher than those in control system (21.1 ± 11.0 % and 73.3 ± 5.6 %). Tandem CW-PFC could accelerate the degradation of EPS into small molecules (such as aromatic protein) by enhancing the electron transfer. Furthermore, microbiome structure analysis indicated that the enrichment of characteristic microorganisms (Anaerovorax) for degradation of protein-related pollutants, and electroactive bacteria (Geobacter and Trichococcus) promoted EPS degradation and electron transfer. The degradation of EPS might be attributed to the up-regulation of the abundances of carbohydrate and amino acid metabolism. This study provided a promising new strategy for synergic mitigation and prevention of bio-clogging in CW by coupling with MFC and photocatalysis.

Seasonal prevalence of bacteria in the outflow of two full-scale municipal wastewater treatment plants

Despite many modern wastewater treatment solutions, the most common is still the use of activated sludge (AS). Studies indicate that the microbial composition of AS is most often influenced by the raw sewage composition (especially influent ammonia), biological oxygen demand, the level of dissolved oxygen, technological solutions, as well as the temperature of wastewater related to seasonality. The available literature mainly refers to the relationship between AS parameters or the technology used and the composition of microorganisms in AS. However, there is a lack of data on the groups of microorganisms leaching into water bodies whose presence is a signal for possible changes in treatment technology. Moreover, sludge flocs in the outflow contain less extracellular substance (EPS) which interferes microbial identification. The novelty of this article concerns the identification and quantification of microorganisms in the AS and in the outflow by fluorescence in situ hybridization (FISH) method from two full-scale wastewater treatment plants (WWTPs) in terms of 4 key groups of microorganisms involved in the wastewater treatment process in the context of their potential technological usefulness. The results of the study showed that Nitrospirae, Chloroflexi and Ca. Accumulibacter phosphatis in treated wastewater reflect the trend in abundance of these bacteria in activated sludge. Increased abundance of betaproteobacterial ammonia-oxidizing bacteria and Nitrospirae in the outflow were observed in winter. Principal component analysis (PCA) showed that loadings obtained from abundance of bacteria in the outflow made larger contributions to the variance in the PC1 factorial axis, than loadings obtained from abundance of bacteria from activated sludge. PCA confirmed the reasonableness of conducting studies not only in the activated sludge, but also in the outflow to find correlations between technological problems and qualitative and quantitative changes in the outflow microorganisms.

Stress response and signalling of a low-temperature bioaugmentation system in decentralized wastewater treatment: Degradation characteristics, community structure, and bioaugmented mechanisms

Low temperatures present challenges for stable wastewater treatment operations in cold regions. Low-temperature effective microorganisms (LTEM) were added as a bioaugmentation strategy at a decentralized treatment facility to improve performance. The effects of a low-temperature bioaugmentation system (LTBS) with LTEM at low temperatures (4 °C) on organic pollutant performance, microbial community changes, and the metabolic pathways of functional genes and functional enzymes were studied. To explore the bioaugmentation mechanism of LTBS based on stress response and signalling. The results showed that the start-up time of the LTBS (S2) with LTEM was shorter (8 days) and that it removed COD and NH₄⁺-N at higher rates (87 % and 72 %, respectively) at 4 °C. LTEM effectively degraded complex macromolecular organics into small molecular organics, and decomposing sludge flocs and the changing the extracellular polymeric substances (EPS) structure removed more organics and nitrogen. LTEM and local microbial communities (nitrifying and denitrifying bacteria) improved the ability of organic matter degradation and denitrification of the LTBS and formed a core microbial community dominated by LTEM (Bacillus and Pseudomonas). Finally, based on the functional enzymes and metabolic pathways of the LTBS, a low-temperature strengthening mechanism consisting of 6 cold stress responses and signal pathways under low temperatures was formed. This study demonstrated that the LTEM-dominated LTBS could provide an engineering alternative for future decentralized wastewater treatment in cold regions.

Effect of Cd(II) shock loading on performance, microbial enzymatic activity and microbial community in a sequencing batch reactor

The performance, microbial enzymatic activity and microbial community of a sequencing batch reactor (SBR) were explored under instantaneous Cd(II) shock loading. After a 24-h Cd(II) shock loading of 100 mg/L, the chemical oxygen demand and NH₄⁺-N removal efficiencies decreased significantly from 92.73% and 99.56% on day 22 to 32.73% and 43% on day 24, respectively, and then recovered to the normal values gradually. The specific oxygen utilization rate (SOUR), specific ammonia oxidation rate (SAOR), specific nitrite oxidation rate (SNOR), specific nitrite reduction rate (SNIRR) and specific nitrate reduction rate (SNRR) decreased by 64.81%, 73.28%, 77.77%, 56.84% and 52.46% on day 23 in comparison with the absence of Cd(II) shock loading, respectively, and they gradually returned to the normal levels. The changing trends of their associated microbial enzymatic activities including dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase were in accordance with SOUR, SAOR, SNOR, SNIRR and SNRR, respectively. Cd(II) shock loading promoted the microbial reactive oxygen species production and lactate dehydrogenase release, indicating that instantaneous shock caused oxidative stress and damaged to cell membranes of the activated sludge. The microbial richness and diversity, and the relative abundance of Nitrosomonas and Thauera obviously decreased under the stress of Cd(II) shock loading. PICRUSt prediction showed that Cd (II) shock loading significantly affected Amino acid biosynthesis, Nucleoside and nucleotide biosynthesis. The present results are conducive to take adequate precautions to reduce the adverse effect on bioreactor performance in wastewater treatment systems.

Response of prokaryotic, eukaryotic and algal communities to heavy rainfall in a reservoir supplied with reclaimed water

The global climate change made the heavy rainfall happen more frequently, and the non-point source pollution caused by it would exacerbate the risk to the water ecological environment. In this study, we took a reservoir (Shahe reservoir, Beijing, China) supplied with reclaimed water as an exapmle to investigate how spatiotemporal changes in the quantity and diversity of prokaryotic, eukaryotic, and algal communities respond to heavy rainfall. Results showed that heavy rainfall could directly impact the composition of the prokaryotic community by introducing amounts of runoff closely associated bacterium especially for the human potential pathogens such as Aliarcobacter, Aeromonas and Pseudomonas in the Shahe reservoir area. While the eukaryotic community was rather stable, and the development and changes in algal communities occurred in the last few days after heavy rainfall. The microbial source tracking through FEAST indicated that Nansha river (S) was the major contributor to the development of all the three concerned communities in the reservoir. The co-occurrence analysis showed that the modules with the highest cumulative abundance in each community were all strongly and positively connected with Chl-a, pH, turbidity, COD and TOC, but negatively correlated with NO₃-N (p < 0.01). The network analysis showed that the eukaryotes played a key role in the interaction network among the three communities, and were more likely to interact with algae and prokaryotes. It was suggested that the controlling of human potential pathogens associated with prokaryotic community should be emphasized at the beginning of the heavy rainfall, but the prevention of the eutrophication bloom should be another focus after the heavy rainfall. This study provided valuable information concerning the role of heavy rainfall on the water ecological environment from the perspective of microbial community.

A functional metagenomics study of soil carbon and nitrogen degradation networks and limiting factors on the Tibetan plateau

Introduction

The Three-River Source Nature Reserve is located in the core area of the Qinghai-Tibetan Plateau, with the alpine swamp, meadow and steppe as the main ecosystem types. However, the microbial communities in these alpine ecosystems, and their carbon and nitrogen degrading metabolic networks and limiting factors remain unclear.

Methods

We sequenced the diversity of bacteria and fungi in alpine swamps, meadows, steppes, and their degraded and artificially restored ecosystems and analyzed soil environmental conditions.

Results

The results indicated that moisture content had a greater influence on soil microbial community structure compared to degradation and restoration. Proteobacteria dominated in high moisture alpine swamps and alpine meadows, while Actinobacteria dominated in low moisture alpine steppes and artificial grasslands. A metabolic network analysis of carbon and nitrogen degradation and transformation using metagenomic sequencing revealed that plateau microorganisms lacked comprehensive and efficient enzyme systems to degrade organic carbon, nitrogen, and other biological macromolecules, so that the short-term degradation of alpine vegetation had no effect on the basic composition of soil microbial community. Correlation analysis found that nitrogen fixation was strong in meadows with high moisture content, and their key nitrogen-fixing enzymes were significantly related to Sphingomonas. Denitrification metabolism was enhanced in water-deficient habitats, and the key enzyme, nitrous oxide reductase, was significantly related to Phycicoccus and accelerated the loss of nitrogen. Furthermore, Bacillus contained a large number of amylases (GH13 and GH15) and proteases (S8, S11, S26, and M24) which may promote the efficient degradation of organic carbon and nitrogen in artificially restored grasslands.

Discussion

This study illustrated the irrecoverability of meadow degradation and offered fundamental information for altering microbial communities to restore alpine ecosystems.

Ecological risk assessment and identification of the distinct microbial groups in heavy metal-polluted river sediments

To assess the health of river ecosystems, it is essential to quantify the ecological risk of heavy metals in river sediments and the structure of microbial communities. As important tributaries of the Tuo River in the upper reaches of the Yangtze River, the Mianyuan River and the Shiting River, are closely related to the economic development and human daily life in the region. This study assessed the ecological risks of heavy-metal-polluted river sediments, the heavy-metal-driven bacterial communities were revealed, and the relationships between the ecological risks and the identical bacterial communities were discussed. The Cd content was significantly greater than the environmental background value, leading to a serious pollution and very high ecological risk at the confluence of the two rivers and the upper reaches of the Mianyuan River. Microbial community analysis showed that Rhodobacter, Nocardioides, Sphingomonas, and Pseudarthrobacter were the dominant bacterial genera in the sediments of the Shiting River. However, the dominant bacterial genera in the Mianyuan River were Kouleothrix, Dechloromonas, Gaiella, Pedomicrobium, and Hyphomicrobium. Mantel test results showed (r = 0.5977, P = 0.005) that the Cd, As, Zn, Pb, Cr, and Cu were important factors that influenced differences in the distribution of sediment bacterial communities Mianyuan and Shiting rivers. A correlation heatmap showed that heavy metals were negatively correlated for most bacterial communities, but some bacterial communities were tolerant and showed a positive correlation. Overall, the microbial structure of the river sediments showed a diverse spatial distribution due to the influence of heavy metals. The results will improve the understanding of rivers contaminated by heavy metals and provide theoretical support for conservation and in situ ecological restoration of river ecosystems.

Pretreatment of septic tank wastewater by packed anaerobic baffled reactor: Pollutant degradation and microbial community succession in different compartments

Anaerobic baffled reactor (ABR) is widely used in rural sewage treatment due to its unique structure, strong impact load resistance, and low energy consumption. However, there is a lack of research on pollutant degradation patterns and microbial community succession patterns in each compartment of ABR. In this study, a packed anaerobic baffled reactor (PABR) was constructed. The effects of T and HRT on the pollutant removal performance of PABR were investigated, and the pollutant degradation and microbial community succession in different compartments of PABR were studied. The results show that the removal rates of COD, NH₄⁺-N, and TN of PABR can reach 85.54 ± 1.08%, 16.94 ± 1.01%, and 5.64 ± 1.18% respectively, and PABR has a good pollutant removal effect. With the extension of HRT, the COD removal rate of PABR increases steadily, and the NH₄⁺-N and TN removal rate of PABR increases to a certain extent. The recommended HRT is 72 h. T has a significant impact on the COD removal effect of PABR. The increase of T in a certain range is conducive to the removal of pollutants by PABR. The COD removal rate of PABR decreases gradually along the flow direction, and the removal of organic matter is mainly concentrated in the first compartment. PABR has good removal capacity for CODss and better nitrogen removal capacity compared with traditional ABR. The richness and diversity of the microbial community in PABR increased gradually along the flow direction. The bacterial species in each compartment were similar but the proportion was different, showing the characteristics of multi-stage and separated phase operation. This study provides a new reference for the application of ABR in rural sewage treatment.

Bioorganic fertilizers improve the adaptability and remediation efficiency of Puccinellia distans in multiple heavy metals-contaminated saline soil by regulating the soil microbial community

Soil salinization and heavy metal (HM) pollution are global environmental problems. Bioorganic fertilizers facilitate phytoremediation, but their roles and microbial mechanisms in natural HM-contaminated saline soils have not been explored. Therefore, greenhouse pot trials were conducted with three treatments: control (CK), manure bioorganic fertilizer (MOF), and lignite bioorganic fertilizer (LOF). The results showed that MOF and LOF significantly increased nutrient uptake, biomass, toxic ion accumulation in Puccinellia distans, soil available nutrients, SOC, and macroaggregates. More biomarkers were enriched in MOF and LOF. Network analysis confirmed that MOF and LOF increased the number of bacterial functional groups and fungal community stability and strengthened their positive association with plants; Bacteria have a more significant effect on phytoremediation. Most biomarkers and keystones play important roles in promoting plant growth and stress resistance in the MOF and LOF treatments. In summary, besides enrichment of soil nutrients, MOF and LOF can also improve the adaptability and phytoremediation efficiency of P. distans by regulating the soil microbial community, with LOF having a greater effect.

Safe purification of rural drinking water by biological aerated filter coupled with ultrafiltration

Water resources of many rural areas are usually lakes or reservoirs, which can be easily affected by run-off, non-point source pollution and are often of poorer quality compared with urban water sources. Drinking water supply in remote rural areas usually suffers from various challenges, such as the high cost of construction and maintenance of centralized drinking water treatment plants and pipe networks, due to the dispersed nature of villages, which are often located in varied and complex topographies. In this study, a combined process comprising biological aerated filter (BAF) combined with ultrafiltration was developed to treat polluted reservoir water. Organic matter indexes, turbidity, and chroma were used as indicators for the evaluation of the system performance. In a long-term experiment lasting 260 days, the combined process was tested under different values of critical operational parameters, including filler types and empty bed contact time (EBCT). Furthermore, the microbial communities in different BAF reactors were carefully evaluated at different times, finding that microorganisms with specific functions were enriched in the various BAF reactors. The combined process reached 85.5 % removal rate of DOC with an EBCT of 45 min and using granule active carbon (GAC) as filler. Most of the effluents of BAF reactors met the requirements for drinking water in China. The combined system showed practical potential for polluted water treatment in some rural areas.

Effects of ultraviolet radiation on microorganism and nitrogen metabolism in sewage under plateau background

The experiments were conducted in the Tibetan plateau environment, and the sewage treatment conditions were designed with ultraviolet (UV) irradiation for 5 min, 10 min, 30 min, and 180 min. The Illumina MiSeq high-throughput sequencing technology was used to analyze the microbiological and metabolomic patterns of the plateau sewage treatment at the experimental scale, and then the response mechanisms of microbial and nitrogen metabolism in sewage treatment were explored. The abundance of metabolism at the first level and global and overview maps at the second level were higher in the plateau environment than in other regions. The KEGG pathway shows the effect of UV on nitrogen metabolism and its aptitude to improving or inhibit it. The two main nitrogen removal processes are nitrification and dissimilatory nitrate reduction. This study reveals the response of activated sludge to UV radiation in a plateau environment from microbiological and metabolomic perspectives, providing ideas and perspectives for the study of water treatment system methods, as well as laying a valuable theoretical foundation for the enhancement of plateau sewage treatment capacity.

Distinctive community assembly enhances the adaptation to extreme environments during hyperthermophilic composting

Hyperthermophilic composting (hTC) is a promising technique for solid waste treatment due to its distinctive microbiomes. However, the assembly process of the hTC microbial community remains unclear. We investigated the assembly process of hTC and explored the underlying drivers influencing community assembly in this work by employing conventional thermophilic composting (cTC) as a comparison group. Our results showed that the two composting treatments have different community assembly processes. Especially for the initial and thermophilic phases, hTC is affected by homogeneous dispersal (48%) and homogeneous selection (44%), respectively, while cTC is controlled by undominant (38%) and homogeneous selection (92%), respectively. Furthermore, random forest models and network results suggested that different factors govern the community assembly in these two composting methods. Specifically, the hTC community increases the stability of the thermophilic community via enhancing the interactions of low-abundance taxa with other operational taxonomic units (OTUs) in community assembly. Our results suggested that the distinctive nature of hTC community assembly may be responsible for its adaptation to extreme environments.

Deciphering the antibiotic resistome and microbial community in municipal wastewater treatment plants at different elevations in eastern and western China

Antibiotic resistance genes (ARGs) as emerging environmental contaminants pose severe global risks to public health and ecosystems. Municipal wastewater treatment plants (WWTPs) are crucial transmitters for the dissemination and propagation of ARGs into receiving water bodies via mobile genetic elements (MGEs). However, the comprehensive and deep deciphering of the diversity, abundance, and potential hosts of ARGs in two distinct altitudinal WWTPs is scarce. In this work, we revealed the elevational distribution characteristics of the resistance genes and microbial community of six WWTPs from two distinct geographical zones: a low-elevation (LE) region (Shandong, 10-22 m above sea level) and a high-elevation (HE) region (Gansu, 1,520-1,708 m above sea level). Significant elevational variations in the diversity and relative abundance of resistance genes were observed. Wastewater treatment could significantly reduce the concentrations of ARGs and MGEs by about 1-2 and 2-3 orders of magnitude, respectively. However, above 69.95% of resistance genes were enriched in effluent. In particular, 24 ARG subtype, 3 MGE subtypes, and 59 bacterial genera were persistent in all samples. More potential hosts for ARGs in LE region and more abundant human gut microbiota in HE region were identified. This work provides helpful information for controlling the spread of ARGs for their management and assessment, thereby mitigating the risks of ARGs in WWTPs.

Response of microbial community to the remediation of neonicotinoid insecticide imidacloprid contaminated wetland soil by Phanerochaete chrysosporium

Imidacloprid (IMI), a typic neonicotinoid insecticide, is widely used and persist in soils with long half-time causing serious threat to ecosystem and human health. It is urgent to develop suitable and effective methods to accelerate it degradation and alleviate its negative impacts in soil. In this study, the introduction of functional microbe white-rot fungus Phanerochaete chrysosporium to remediate IMI contaminated wetland soil was carried out. The remediation performance and the response of the soil microbial community were examined. The results showed that P. chrysosporium could improve the degradation of IMI in soil no matter the soil was sterilized or not. The bioaugmentation was especially observed in non-sterilized soil under the inoculation patterns of FE and SP with the maximum IMI degradation rate of 91% and 93% in 7 days, respectively. The invertase activity in soil was also enhanced with P. chrysosporium inoculation. Microbial community analysis revealed that P. chrysosporium inoculation could increase the diversity and richness of bacterial community, and stimulate some IMI degraders genera including Ochrobactrum, Leifsonia, Achromobacter, and Bacillus. Moreover, the xenobiotic degradation and metabolism pathway was generally enhanced with P. chrysosporium inoculation based on PICRUSt analysis. These obtained results demonstrated that the introduction of white-rot fungus is of great potentially enabling the remediation of neonicotinoids contaminated soil.

Complexing agents-free bioelectrochemical trickling systems for highly-efficient mesothermal NO removal: The role of extracellular polymer substances

The biological treatments are promising for nitric oxide (NO) reduction, however, the biotechnology has long suffered from high demands of NO-complexing agents (i.e., Fe(II)EDTA), leading to extra operation costs. In this study, novel complexing agents-free bioelectrochemical systems have been developed for direct NO reduction. The electricity-driven bioelectrochemical trickling system (ED-BTS, a denitrifying biocathode driven by the external electricity and an acetate-consuming bioanode) achieved approximately 68% NO removal without any NO-complexing agents, superior to the bioanode-driven BTS and open-circuit BTS. The extracellular polymeric substances from the biofilms of ED-BTS contained more polysaccharides, humic substrates, and hydrophobic tryptophan that were beneficial for NO reduction. Additionally, the external electricity altered the microbial community toward more denitrifying bacteria and a higher abundance of NO reduction genes (nosZ and cnorB). This study provides a comprehensive understanding of microbial behaviors on the adsorption and reduction of NO and proposes a promising strategy for mesothermal NO biotreatment.

Deciphering the microbial community structures and functions of wastewater treatment at high-altitude area

Introduction: The proper operation of wastewater treatment plants is a key factor in maintaining a stable river and lake environment. Low purification efficiency in winter is a common problem in high-altitude wastewater treatment plants (WWTPs), and analysis of the microbial community involved in the sewage treatment process at high-altitude can provide valuable references for improving this problem. Methods: In this study, the bacterial communities of high- and low-altitude WWTPs were investigated using Illumina high-throughput sequencing (HTS). The interaction between microbial community and environmental variables were explored by co-occurrence correlation network. Results: At genus level, Thauera (5.2%), unclassified_Rhodocyclaceae (3.0%), Dokdonella (2.5%), and Ferribacterium (2.5%) were the dominant genera in high-altitude group. The abundance of nitrogen and phosphorus removal bacteria were higher in high-altitude group (10.2% and 1.3%, respectively) than in low-altitude group (5.4% and 0.6%, respectively). Redundancy analysis (RDA) and co-occurrence network analysis showed that altitude, ultraviolet index (UVI), pH, dissolved oxygen (DO) and total nitrogen (TN) were the dominated environmental factors (p < 0.05) affecting microbial community assembly, and these five variables explained 21.4%, 20.3%, 16.9%, 11.5%, and 8.2% of the bacterial assembly of AS communities. Discussion: The community diversity of high-altitude group was lower than that of low-altitude group, and WWTPs of high-altitude aeras had a unique microbial community structure. Low temperature and strong UVI are pivotal factors contributing to the reduced diversity of activated sludge microbial communities at high-altitudes.

Bioaugmentation performance for moving bed biofilm reactor (MBBR) treating mariculture wastewater by an isolated novel halophilic heterotrophic nitrification aerobic denitrification (HNAD) strain (Zobellella B307)

Moving bed biofilm reactor (MBBR) demonstrates weak nitrogen removal for mariculture wastewater treatment under high salinity environment. An isolated novel halophilic heterotrophic nitrification aerobic denitrification (HNAD) strain (Zobellella B307) was applied in MBBR process to enhance nitrogen removal. Results showed that strain Zobellella B307 could remove 90.9% ammonia nitrogen (NH₄⁺-N) and 97.1% nitrate nitrogen (NO₃^--N) after 10 h cultivation, and strong resistance to salinity variation (high growth and nitrogen removal efficiency with salinity of 65‰) was observed. Besides, the chemical oxygen demand (COD), NH₄⁺-N and NO₃^--N removal reached 95.6%, 94.4% and 85.7% with the strain added into MBBR process. In addition, microbial community structure analysis reflected that the strain Zobellella B307 successfully proliferated (the relative abundance increased to 2.33%). The HNAD bacteria abundance increased and dominated during the nitrogen removal process with the strain inoculation. A microbial functional analysis revealed that the main dominant functional categories (carbohydrate metabolism and amino acid metabolism) increased with the bioaugmentation of strain Zobellella B307, thus improving the nitrogen removal.

Epichloë endophyte interacts with saline-alkali stress to alter root phosphorus-solubilizing fungal and bacterial communities in tall fescue

Epichloë endophytes, present in aboveground tissues, modify belowground microbial community. This study was conducted to investigate endophyte (Epichloë coenophialum) associated with tall fescue (Lolium arundinaceum) interacted with an altered saline-alkali stress (0, 200 and 400 mmol/l) to affect the belowground phosphorus solubilizing microorganisms including phosphorus solubilizing fungi (PSF) and bacteria (PSB). We found that a significant interaction between E. coenophialum and saline-alkali stress occurred in the diversity and composition of PSF in tall fescue roots. Under saline-alkali stress conditions (200 and 400 mmol/l), E. coenophialum significantly increased the PSF diversity and altered its composition in the roots, decreasing the relative abundance of dominant Cladosporium and increasing the relative abundance of Fusarium. However, there was no significant interaction between E. coenophialum and saline-alkali stress on the PSB diversity in tall fescue roots. E. coenophialum significantly reduced the diversity of PSB in the roots, and E. coenophialum effects did not depend on the saline-alkali stress treatment. Structural equation modeling (SEM) showed that E. coenophialum presence increased soil available phosphorus concentration under saline-alkali stress primarily by affecting PSF diversity instead of the diversity and composition of PSB.