Nitrogen pollution is a major ecological challenge globally, and riverine nitrogen cycling is influenced by both human activities and hydrological variability. In this study, we combined metagenomic sequencing, the Soil and Water Assessment Tool (SWAT), and machine learning to systematically elucidate the response mechanisms of microbially mediated nitrogen cycling to pollution inputs and hydrological fluctuations in sediments of the Weihe River Basin. The results showed significant variations of microbial communities and nitrogen cycling genes in different pollution source areas, especially in the low water period. Nitrogen removal genes (nirS, norB, nosZ, hzo) were enriched in point source-dominated areas, whereas nitrogen fixation genes (nifK, nifD) were more abundant in non-point source-dominated areas. Key bacteria-gene co-occurrence network showed a larger scale but stronger competitive interactions in point source-dominated areas and low water period. Redundancy analysis and structural equation model indicated that nitrogen cycling was strongly influenced by changes in runoff and pollution inputs in the high and low water period, and that hydrology and pollution inputs primarily affected nitrogen cycling by regulating microbial communities. Interpretable machine learning further revealed nonlinear responses of key nitrogen metabolic pathways to substrate conditions. NO3--N significantly promoted denitrification above 1.95mg/kg, and NH4+-N exerted contrasting effects on DNRA and anammox. Two-dimensional partial dependence analysis revealed an optimal denitrification window under the combination of relatively high precipitation and intermediate point-source proportions (40%-55%). This study provides a theoretical basis for the precise regulation and management of nitrogen pollution in watersheds.

Nitrous oxide (N2O) emissions from biological wastewater treatment pose a disproportionate challenge to carbon neutrality, as small releases substantially elevate the greenhouse gas footprint. Conventional treatment systems operate with aerobic phases lasting hours, during which oxygen suppresses nitrous oxide reductase (NosZ) activity and allows dissolved N2O to accumulate. Shortening these phases to the minute scale through dynamic feedback-controlled aeration could couple N2O production and reduction, but whether frequent oxic-anoxic cycling enables NosZ reactivation during postoxic anoxia remains unclear. In 1 L lab-scale suspended-growth reactors, we compared oxygen-only pulsing without imposed anoxia (continuous perturbation, CP) and paired oxic-anoxic cycling (intermittent perturbation, IP). At an oxygen ceiling of 2 mg/L, CP increased the N2O fraction of gaseous nitrogen (GN) to 0.25-0.74, whereas IP maintained a low N2O-N/GN ratio of 0.02-0.24 while releasing 79% of nitrified ammonium-N as GN. After adaptation, dissolved N2O consumption rates were 4-6.5 times higher under IP than CP. Metaproteomic evidence confirmed NosZ enrichment under IP, with Hyphomicrobium as a key contributor. These results establish minute-scale oxic-anoxic cycling as a key operational prerequisite for NosZ reactivation during postoxic anoxia, recoupling N2O production and reduction, and providing a practical framework for reducing N2O emissions through PLC-based aeration control without retrofitting.

Microbially induced calcite precipitation (MICP) is an emerging method for mitigating scour and erosion. The present study experimentally investigates the efficacy of MICP as a local scour countermeasure for offshore wind turbine monopile foundations under both clear water and live-bed conditions. Bacteria were enriched using activated sludge. Analyses conducted included urease activity monitoring, unconfined compression testing, and examination using scanning electron microscopy. Various depths for the MICP protection elevation were tested in clear water conditions, and the resulting scour topography was mapped using photogrammetry techniques. Investigations were conducted on bedform migration and leading-edge scour upstream of the MICP protection, considering various protection elevations. The results indicated that MICP protection can provide effective scour protection under both clear water and live-bed conditions. Discussions in this study also extend to the erosion and potential collapse of the MICP protection structure. Flow undercut rate were also examined for evaluating potential failure of MICP protection structures, and the elevation of MICP protection has a significant influence on mitigating flow undercutting. Full protection efficiency was observed under clear water conditions when the MICP protection elevation was at the bed level and the flow intensity was relatively low (V/Vc = 0.65), while the highest average protection efficiency (47.73%) among all flow intensities was recorded when the MICP protection elevation was at 0.6D below the bed.

The uncontrolled release of organic micropollutants (OMPs) from wastewater treatment plants highlights a failure to synergize co-metabolic and reactive oxygen species (ROS)-driven biodegradation pathways. Here, we demonstrate that engineered redox cycling—dynamic fluctuations between oxic and anoxic conditions—fundamentally reshapes microbial metabolism and OMP reaction networks to dramatically enhance removal. Using an integrated multi-omics approach centered on paired mass distance (PMD) reactomics, we show that redox cycling increased the removal of 32 diverse OMPs from a baseline of 32% up to 67%. This enhancement was driven by a complete restructuring of degradation mechanisms: cycling stimulated microbial amino acid and fatty acid metabolism by up to 42%, which coupled to controlled ROS production where oxidative pathways (+15.995 Da) accounted for 47% of transformations under intermittent aeration. We mapped distinct “enzymatic fingerprints,” with strong correlations (r > 0.7) linking Proteobacteria monooxygenases to oxidative reactions and Rhodobacteraceae dehydrogenases to reductive ones (+2.016 Da), revealing clear functional specialization. Ultimately, the redox regime dictates the entire OMP transformation network topology, shifting pathways from simple hydroxylation to complex, multi-step networks. This work provides a mechanistic framework establishing redox manipulation as a powerful strategy to synergistically activate degradation pathways, allowing existing infrastructure to meet stringent discharge regulations. ### Competing Interest Statement The authors have declared no competing interest.

Dynamic oxygen fluctuations in activated sludge were investigated to enhance valuable biochemical production during wastewater treatment. Batch experiments compared constant aeration with rapid cycling between oxygen-rich and oxygen-poor states. Fluctuating oxygen concentrations (0-2 mg/L) significantly increased production of valuable biochemicals compared to constant oxygen concentration (2 mg/L). Continuous oxygen perturbations increased free amino acids by 35.7 f 7.6 % and free fatty acids by 76.4 f 13.0 %, while intermittent perturbations with anoxic periods enhanced free amino acids by 42.4 f 8.1 % and free fatty acids by 39.3 f 7.7 %. Fourteen standard amino acids showed significant increases, and most fatty acids had carbon chain lengths between C12-C22. Mechanistically, oxygen perturbations activated FNR and ArcA regulons, resulting in lower relative abundances of TCA cycle enzymes and higher abundances of amino acid and fatty acid biosynthetic enzymes. These findings demonstrate that controlled oxygen fluctuations in wastewater treatment can enhance the biochemical value of activated sludge with minimal process modifications, facilitating resource recovery.

Aquatic ecosystems are facing severe threats from climate change, with rising temperatures as a major driving force posing a significant challenge to their ecological balance. Microorganisms constitute the majority of biomass in the water ecosystems and mediate the flux of carbon, nitrogen, sulfate and other essential nutrients. Climate warming profoundly influences microbial communities by shaping their distribution and ecological roles in the ecosystem, and in turn microorganisms play a significant role in climate feedback. The Yellow River, China’s second-longest river, is crucial for agricultural irrigation and provides drinking water for millions, yet little is known about microbial community adaptations under future warming scenarios in the system. In this study, we analyzed a publicly available metagenomic dataset from Yellow River water samples that were previously subjected to temperature treatments of 23, 26, 29, 32, and 35 degrees Celsius. We employed metagenomic analysis to identify how gradually increasing temperatures affected microbial community profiles. The study identified 140 species tolerant to high temperatures, showing a significant increase in abundance with elevated temperatures. The elevated temperature stress impacted the network properties of microbial communities substantially. Certain temperature-tolerant species were identified as hubs in the network across five temperatures, with their number increasing with temperature. Deltaproteobacteria bacterium was present at all five temperatures, while Parcubacteria bacterium, Parvularcula sp ., Phenylobacterium sp ., Phycisphaeraceae bacterium , and Sphingobium xenophagum were only present at high temperatures of 32 °C and 35 °C. The percentage of taxa nodes connected to tolerant hubs in the overall network rose from 57.48% to 95.94%, indicating the growing importance of these tolerant hubs. The positive connections among these tolerant hubs also increased, with the number of positive edges rising from 1166 to 2811, indicating a potential collaborative relationship among these taxa in response to temperature stress. These findings suggest that tolerant hubs may initially respond to temperature stress and subsequently transfer this function to other species through cooperative interactions. Understanding these microbial dynamics is crucial for developing strategies to maintain freshwater ecosystem health amid climate change. ### Competing Interest Statement The authors have declared no competing interest.

Aquatic ecosystems are facing severe threats from climate change, with rising temperatures as a major driving force posing a significant challenge to their ecological balance. Microorganisms constitute the majority of biomass in the water ecosystems and mediate the flux of carbon, nitrogen, sulfate and other essential nutrients. Climate warming profoundly influences microbial communities by shaping their distribution and ecological roles in the ecosystem, and in turn microorganisms play a significant role in climate feedback. The Yellow River, China's second-longest river, is crucial for agricultural irrigation and provides drinking water for millions, yet little is known about microbial community adaptations under future warming scenarios in the system. In this study, water from the Lanzhou section of the Yellow River was heated to temperatures of 23 degrees C, 26 degrees C, 29 degrees C, 32 degrees C, and 35 degrees C to investigate the impact of elevated temperature on the microbial adaptations and interactions. The metagenomics approach was employed to identify the effect of gradually increasing water temperatures on the profiles of microorganisms in the Yellow River. The study identified 140 species tolerant to high temperatures, showing a significant increase in abundance with elevated temperatures. The elevated temperature stress impacted the network properties of microbial communities substantially. Certain temperature-tolerant species were identified as hubs in the network across five temperatures, with their number increasing with temperature. Deltaproteobacteria bacterium was present at all five temperatures, while Parcubacteria bacterium, Parvularcula sp., Phenylobacterium sp., Phycisphaeraceae bacterium, and Sphingobium xenophagum were only present at high temperatures of 32 degrees C and 35 degrees C. The percentage of taxa nodes connected to tolerant hubs in the overall network rose from 57.48% to 95.94%, indicating the growing importance of these tolerant hubs. The positive connections among these tolerant hubs also increased, with the number of positive edges rising from 1166 to 2811, indicating a potential collaborative relationship among these taxa in response to temperature stress. These findings suggest that tolerant hubs may initially respond to temperature stress and subsequently transfer this function to other species through cooperative interactions. Understanding these microbial dynamics is crucial for developing strategies to maintain freshwater ecosystem health amid climate change.

Cadmium (Cd) contamination in coastal regions poses severe environmental risks, yet bacterial defense mechanisms against Cd remain poorly understood. This study unveils distinct tolerant strategies of two highly Cd-tolerant bacteria isolated from the Yangtze River estuary: Comamonas sp. Y49 and Aeromonas sp. Y23. We exposed two bacterial strains to Cd2 + concentrations ranging from sub-lethal to near-lethal levels, based on their minimum inhibitory concentrations, to investigate their stress response mechanisms. The cellular adaptations were comprehensively analyzed through transcriptomic profiling and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS). Transcriptomic analyses revealed that both strains significantly stimulated carbon, nitrogen and sulfur metabolism under Cd stress for maintaining essential substance and energy resources. They both enhanced reactive oxygen scavenger and polyamine biosynthesis gene regulation, suggesting a shared strategy for mitigating oxidative stress. Strain Comamonas sp. Y49 showed a 2.97-fold increase in metal efflux gene regulation and secreted extracellular polysaccharide-like substances with SEM-EDS detecting 0.50 % Cd on cell surfaces, while Aeromonas sp. Y23 potentially reduced Cd uptake by forming long-chain cellular structures. Besides, Comamonas sp. Y49 downregulated motility genes by 2.07-fold, while Aeromonas sp. Y23 upregulated them by 1.12-fold, indicating divergent biofilm formation strategies. This study provides novel insights into bacterial Cd resistance, revealing strain-specific adaptive mechanisms that combine metabolic rewiring, morphological changes, and molecular defense strategies. Our findings provide valuable insights on bacterial adaptations to metal stress and establish a molecular foundation for developing microbial-based strategies to address metal contamination in estuarine environments.

Since the Great Oxidation Event 2.4 billion years ago, microorganisms have evolved sophisticated responses to oxidative stress. These ancient adaptations remain relevant in modern engineered systems, particularly in conventional activated sludge (CAS) processes, which serve as significant reservoirs of antibiotic resistance genes (ARGs). While ROS-induced stress responses are known to promote ARG enrichment/emergence in pure cultures, their impact on ARG dynamics in wastewater treatment processes remains unexplored. Shotgun-metagenomics analysis of two hospital wastewater treatment plants showed that only 35-53 % of hospital effluent resistome was retained in final effluent. Despite this reduction, approximately 29-36 % of ARGs in CAS showed higher abundance than upstream stages, of which 20-22 % emerged de novo. Beta-lactamases and efflux pumps constituted nearly 47-53 % of these enriched ARGs. These ARGs exhibited significant correlations (p < 0.05) with ROS stress response genes (oxyR, soxR, sodAB, katG and ahpCF). The CAS resistome determined 58-75 % of the effluent ARG profiles, indicating treatment processes outweigh influent composition in shaping final resistome. Proof-of-concept batch reactor experiments confirmed increased ROS and ARG levels under high dissolved oxygen (8 mg/L) compared to low oxygen (2 mg/L) concentrations. Untargeted metaproteomics revealed higher expression of resistant proteins (e.g., OXA-184, OXA-576, PME-1, RpoB2, Tet(W/32/O)) under elevated ROS levels. Our findings demonstrate that CAS processes actively shape effluent resistome through ROS-mediated selection, indicating that treatment processes, rather than initial wastewater composition, determine final ARG profiles. This study indicates that the emergence of ARGs needs to be considered as an integral aspect of wastewater treatment design and operation to prevent antibiotic resistance dissemination.

Neuroendocrine compounds discharged into wastewater systems represent an emerging challenge at the intersection of human physiology and environmental microbiology. l-norepinephrine (L-NE), which has been recognized to potentiate growth of human and animal bacterial pathogens, is discharged in sewage through urine and faeces. While extensive pure culture studies have established l-NE's capacity to modulate bacterial virulence through iron acquisition and quorum sensing pathways, its impact on complex microbial communities, where intricate metabolic networks and interspecies interactions dominate, remains largely unexplored. This knowledge gap is particularly critical as urbanization drives increasing neuroendocrine compound loads in wastewater influents in metropolitan areas. Through parallel treatments of l-NE (1 × 10⁻⁵ M to 1 × 10⁻⁴ M), dextrose, and H₂O₂ in municipal and agricultural wastewater communities, we uncovered sophisticated metabolic and regulatory mechanisms that challenge the conventional understanding of microbial substrate utilization. Despite containing 10-fold less carbon, l-NE treatments achieved superior growth (10⁸ CFU mL⁻¹) while maintaining Pseudomonadaceae-dominated communities. Targeted metaproteomics revealed coordinated upregulation of oxidative stress genes (oxyR, soxRS) and antioxidant enzymes, while proteome-constrained metabolic modeling demonstrated distinct pathway modulation in central carbon and nitrogen metabolism. Notably, when compared to dextrose-supplemented controls, representing typical carbon substrate utilization, l-NE treatments showed similar taxonomic profiles without preferential enrichment of known pathogenic families. However, l-NE significantly enhanced autoinducer gene (luxS, qseC) expression, suggesting increased virulence potential through community-level metabolic reprogramming. These findings reveal l-NE as a potent modulator of microbial community dynamics in engineered ecosystems, with important implications for treatment process stability and downstream environmental impacts.

Organic micropollutants （OMPs) in wastewater present significant environmental challenges, but effective removal strategies are hindered by our limited understanding of their co-metabolic biodegradation. We aim to elucidate the microbial enzymes, metabolic pathways, and community members involved in OMP co-metabolic degradation, thereby paving the way for more effective wastewater treatment strategies. We integrated multi-omics (metagenomics, metaproteomics, and metabolomics) and functional group analysis to investigate 24 OMPs under three aeration conditions. Our findings reveal that oxidoreductases, particularly cytochrome P450s and peroxidases, are crucial for recalcitrant OMPs containing halogen groups (-Cl, -F) like fluoxetine and diuron. Hydrolases, including amidases, are instrumental in targeting amide-containing (-CONH₂) OMPs such as bezafibrate and carbamazepine. Regarding microbial metabolism involved in OMP co-metabolic degradation, we found that amino acid metabolism is crucial for degrading amine-containing (-NH₂) OMPs like metoprolol and citalopram. Lipid metabolism, particularly for fatty acids, contributes to the degradation of carboxylic acid (-COOH) containing OMPs such as bezafibrate and naproxen. Finally, with Actinobacteria, Bacteroidetes, and Proteobacteria emerging as primary contributors to these functionalities, we established connections between OMP functional groups, degradation enzymes, metabolic pathways, and microbial phyla. Our findings provide generalized insights into structure-function relationships in OMP co-metabolic degradation, offering the potential for improved wastewater treatment strategies.

Climate warming presents a critical challenge to global ecosystems, with rising temperatures inducing the emergence of antibiotic resistance genes (ARGs) in aquatic environments. Given the natural correlation between rising temperatures and declining oxygen levels in aquatic systems, we hypothesized that decoupling temperature and oxygen stress would reveal regulatory mechanisms mitigating ARG expression under future warming scenarios. Through transcriptomic analysis of Escherichia coli under temperature upshift (TU), dissolved oxygen upshift (DOU), and dissolved oxygen downshift (DOD), we identified 101 distinct regulons with 8 showing significant regulation (|log₂FC| > 1.5). Key regulons ( cusR , mhpR , pdhR ) exhibited parallel regulation under TU and DOD but opposite patterns under DOU, revealing mechanistic links between temperature and oxygen stress through shared regulatory networks involving oxidative stress regulators ( oxyR - metR ) and aerobic respiration control ( arcA - betI ). Evolved strains from controlled temperature-oxygen fluctuations demonstrated sophisticated metabolic reprogramming, including enhanced carbohydrate metabolism, nucleotide biosynthesis, and putrescine degradation. These strains exhibited optimized energy metabolism through reduced downregulation of ATP synthase subunits and NADH dehydrogenase complex genes, preserving electron transport chain function under thermal stress. Simultaneously, they displayed strategic ROS management with reduced upregulation of peroxiredoxin ( ahpF ) and Cu/Zn-SOD ( sodC ), while reversing Fe-SOD ( sodB ) expression patterns. To validate these mechanisms, we conducted independent batch reactor experiments with two dissolved oxygen conditions (2-8 mg/L) using intermittent perturbation patterns. Non-targeted metaproteomic analysis revealed that lowered oxygen levels (2 vs. 8 mg/L) triggered comprehensive reconfiguration of antimicrobial resistance mechanisms, including downregulation of penicillin-binding proteins, alanine racemase, and cationic antimicrobial peptide resistance systems, while modulating two-component regulatory networks. Our findings reveal coordinated regulatory networks optimizing energy metabolism, ROS management, and antibiotic resistance, suggesting oxygen management strategies could mitigate climate warming effects on antibiotic resistance in aquatic environments. ### Competing Interest Statement The authors have declared no competing interest. Royal Society of New Zealand, https://ror.org/04tajb587, MFP-UOA2018

As the global transition toward circular wastewater treatment intensifies, extracellular polymeric substances (EPS) have emerged as valuable targets for resource recovery. Although most related efforts have focused on aerobic granular sludge, conventional activated sludge systems, which account for most global wastewater treatment, remain underexploited. Building on the established link between oxidative stress and EPS biosynthesis in pure strains, it is proposed that strategically manipulating oxygen exposure patterns to intensify oxidative stress in activated sludge microbial communities could enhance EPS production. To test this, this study applied continuous oxygen perturbation under aerobic exposure to intensify oxidative stress. Compared to a stable oxygen condition simulating typical wastewater aeration, the perturbation considerably enhanced EPS yield to 74.4 mg/L/day, a 90.5 % increase over the stable condition (39.0 mg/L/day). To validate the role of oxidative stress in EPS enhancement, intermittent anoxic phases were introduced into the perturbation pattern to relieve oxidative stress, causing the EPS-enhancing effect to disappear, with yield dropping to 9.8 mg/L/day. Mechanistically, intensified oxidative stress under aerobic continuous perturbation was primarily driven by elevated reducing substrates for non-respiratory flavoenzymes, exemplified by glutamate synthase, glutathione reductase, and dihydrolipoamide dehydrogenase, which are prone to generate H2O2 as an unintended metabolic byproduct. Among the multiple microbial groups contributing to H2O2 production, Methylophilaceae, Comamonadaceae, and Rhodobacteraceae were distinguished by simultaneously exhibiting upregulation of EPS biosynthesis proteins, suggesting that taxa within these families collectively mediated both H2O2 production and EPS enhancement. By modulating aeration, this study offers a chemical-free, controllable strategy for enhancing EPS production within conventional activated sludge systems.

Climate change threatens freshwater ecosystems, potentially intensifying cyanobacterial blooms and antibiotic resistance. We investigated these risks in Cosseys Reservoir, New Zealand, using short-term warming simulations (22 °C, 24 °C, and 27 °C) with additional oxidative stress treatments. A metagenomic analysis revealed significant community shifts under warming. The cyanobacterial abundance increased from 6.11% to 20.53% at 24 °C, with Microcystaceae and Nostocaceae proliferating considerably. The microcystin synthesis gene (mcy) cluster showed a strong association with cyanobacterial abundance. Cyanobacteria exhibited enhanced nutrient acquisition (pstS gene) and an upregulated nitrogen metabolism under warming. Concurrently, antibiotic resistance genes (ARGs) increased, particularly multidrug resistance genes (50.82% of total ARGs). A co-association network analysis identified the key antibiotic-resistant bacteria (e.g., Streptococcus pneumoniae and Acinetobacter baylyi) and ARGs (e.g., acrB, MexK, rpoB2, and bacA) central to resistance dissemination under warming conditions. Oxidative stress exacerbated both cyanobacterial growth and ARGs’ proliferation, especially efflux pump genes (e.g., acrB, adeJ, ceoB, emrB, MexK, and muxB). This study demonstrated that even modest warming (2–5 °C) could promote both toxic cyanobacteria and antibiotic resistance. These findings underscore the synergistic effects of temperature and oxidative stress posed by climate change on water quality and public health, emphasizing the need for targeted management strategies in freshwater ecosystems. Future research should focus on long-term impacts and potential mitigation measures.

Nitrous oxide (N2O) is a potent greenhouse gas, with a global warming potential nearly 300 times that of carbon dioxide, and its emission from wastewater treatment plants is a growing environmental concern. In this study, we investigated the effects of intermittent perturbation with high-frequency aerobic-anoxic cycling on N2O reduction in activated sludge systems. The study aimed to enhance N2O reductase (N2OR) activity and N2O reduction potential by optimizing redox state cycling. Six bioreactors were operated under different aeration patterns-constant aerobic (CA), continuous perturbation (CP), and intermittent perturbation (IP) - at two dissolved oxygen levels (2 mg/L and 8 mg/L). Results indicated that IP conditions significantly increased N2OR activity, resulting in higher N2O consumption rates compared to the other aeration patterns. Metagenomic and metaproteomic analyses revealed Hyphomicrobium as a key microorganism contributing to N2O reduction, with increased enzyme abundance and activity under IP conditions. The frequent aerobic-anoxic transitions were found to enhance electron availability for N2OR, facilitating more efficient N2O reduction. These findings suggest that intermittent aeration, particularly with high-frequency cycling, can be an effective strategy for mitigating N2O emissions in wastewater treatment systems. This approach has the potential to improve the environmental sustainability of wastewater treatment by leveraging microbial dynamics and enzyme activity to reduce greenhouse gas emissions. ### Competing Interest Statement The authors have declared no competing interest.

Contaminants of Emerging Concern (CECs) are a class of contaminants that are commonly found in urban wastewater treatment plants (WWTP) at low concentrations. These compounds include antibiotic drugs, personal care products, and industrial chemicals, which are widely used in modern society. Although they provide undeniable benefits in our daily lives, their accumulation in the environment poses a significant risk to human health and the ecosystem. Due to the incomplete removal of these compounds by traditional WWTPs, there is a need to understand the interactions between microbes and CECs to develop effective solutions to this environmental challenge. Pseudomonas putida is a bacterium commonly found in water-related habitats, including freshwater streams, forests, and WWTPs. It is known for its ability to degrade various organic compounds, making it a suitable model for understanding the linkages between bacterial enzymes and CECs found in WWTPs. In this study, isolated Pseudomonas putida strain KT2440 was cultured in lab-scale reactors to mimic the WWTP environment. The degradation of this isolated strain towards different groups of CECs were studied over a 24-hour period using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Mass spectrometry-based quantitative proteomics was also performed at different sampling points to establish a linkage between the enzyme expression profile of this strain and its degradation of CECs via bioinformatics analysis. The results of this study demonstrated that Pseudomonas putida KT2440 is capable of degrading atrazine, acetamiprid, carbendazim, diclofenac acid, erythromycin, and sulfamethazine at lab scale. At the 20-hour time point, the enzyme expression profile indicated a high protein abundance of various oxidoreductases that could explain the observed CEC degradation.The study's findings provide important insights into the potential of Pseudomonas putida as a bioremediation agent for CECs in WWTPs. The degradation of CECs by Pseudomonas putida KT2440 is a significant contribution to the bioremediation process, and its enzyme expression profile can serve as a case study for more complex interactions of microbes and CECs in real WWTPs. Furthermore, this study supports the potential of Pseudomonas putida as a promising strain for various bioremediation applications. Finally, this study's results can help develop more efficient and effective methods for removing CECs from wastewater, which can contribute to the protection of public health and the environment. ### Competing Interest Statement The authors have declared no competing interest.

Bed solidification methods are widely employed for mitigating local scour. This study primarily examines the geometric aspects that influence bed solidification protections, including protection thickness, angle, lateral extent, and placement depth. Scour topography and longitudinal scour profile across various test conditions have also been discussed. Additionally, a schematic discussion of the interaction between flow patterns corresponding to different protection shapes and their resulting scour patterns are presented. The influences of different geometric aspects on equilibrium scour depth have also been studied. Furthermore, an integrated approach combining riprap and bed solidification protection methods has been examined experimentally.

The specific impacts of oxygen perturbation on microbial communities and their synthesis of metabolites remain unclear. We systematically explored how oxygen perturbations alter microbial growth, subsequently affecting the abundance of functional genes and promoting the synthesis of metabolites such as amino acids. Analysis of microbial community structure indicates dynamic stability under oxygen perturbations, with only a fraction of the microbial abundance being altered. By comparing the abundance of functional genes with metabolic features, we revealed how changes in the microbial community impact the overall system performance. Amino acid biosynthesis has an enhanced potential under conditions of oxygen perturbation. Through biological and statistical correlation analyses, we identified microbial species significantly correlated with the efficiency of target metabolic reactions under oxygen perturbations. Mycolicibacterium madagascariense, Mycolicibacterium fortuitum, and Burkholderia pseudomallei displayed strong associations with proline and tryptophan synthesis reactions. Moreover, the abundance of microbial genera including Labrys, Actinomyces, and Nitrosopumilus exhibited a highlysignificant positive correlation with metabolite abundance in enriched metabolic pathways under oxygen perturbations. These results suggest that microbial systems might achieve dynamic stability in community structure under oxygen perturbations, while exhibiting slightly differential metabolic potentials. Notably, enhanced efficiency in amino acid biosynthesis could help to assimilate more carbon and nitrogen resources in activated sludge during wastewater treatment. ### Competing Interest Statement The authors have declared no competing interest.

Microplastics (MPs) have become an emerging anthropogenic pollutant, and their ability to sorb contaminants potentially enhances the threats to the ecosystem. Only a few studies are available to understand the combined effects of microplastics and other pollutants. The present study investigated the sorption of perfluorooctane sulfonic acid (PFOS) onto polystyrene microplastics (PS-MPs) at varying concentrations, using molecular dynamics simulation (MDS) to preliminarily explore the adsorption behavior. The MDS results revealed negative interaction energies between PFOS and PS-MPs, underscoring PS-MPs' role as a potential adsorbent for PFOS in an aqueous solution. Thereafter, zebrafish embryos were employed to explore the toxic effects of combined exposure to PS-MPs and PFOS. Fluorescence and Scanning Electron Microscopy (SEM) suggested PS-MP accumulation individually and in combination with PFOS on the embryonic chorion membrane. As a result, the exposed group showed increased inner pore size of the chorionic membrane and accelerated heartbeat, indicating hypoxic conditions and hindered gaseous exchange. PS-MPs aggravated the toxicity of PFOS during larval development manifested by delayed hatching rate, increased mortality, and malformation rate. Additionally, increased ROS accumulation and altered antioxidant enzymatic status were observed in all the exposed groups suggesting perturbation of the redox state. Additionally, co-exposure of zebrafish larvae to PS-MPs and PFOS resulted in an abrupt behavioral response, which decreased AChE activity and altered neurotransmitter levels. Taken together, our results emphasize that PS-MPs can act as a potential vector for PFOS, exerting synergistic toxic effects in the aquatic environment, and hence their health risks cannot be ignored.

Understanding the interplay between oxygen conditions and microbial activities in an activated sludge system is crucial for the optimization of wastewater treatment processes. This study explores the influence of various aeration patterns and dissolved oxygen (DO) levels on the microbial metabolic activities, with a particular focus on the synthesis and release of soluble microbial products (SMP), and the regulation of key metabolic genes and enzymes. The activated sludge system underwent different aeration patterns, including constant aeration, continuous perturbation, and intermittent perturbation under two distinct DO levels of 2mg/L and 8mg/L. We employed a combination of multi-omics techniques (metagenomics, metaproteomics, and metabolomics) along with chemical analytical methods for comprehensive sample analysis. Our results reveal an increased intracellular accumulation of amino acids and enhanced release of protein under the conditions of oxygen perturbation. Furthermore, elevated DO levels fostered the accumulation of poly-3-hydroxybutyrate intracellularly and the release of protein and fatty acids as SMP. This outcome is associated with the abundance of key metabolic genes and enzymes, thereby highlighting the metabolic flexibility of microbes under different oxygen conditions. These findings offer valuable insights into microbial metabolic dynamics under varying oxygen conditions, thereby providing guidance for more efficient and sustainable strategies in wastewater treatment and resource recovery. ### Competing Interest Statement The authors have declared no competing interest.