Spread of antibiotic resistance genes (ARGs) in agricultural soils threatens ecological and public health. Functionalized biochars hold promise for remediating biological contaminants, yet the performance of Fe/Mn oxide-loaded biochars (Fe/Mn-MBCs) in mitigating soil ARG pollution remains unclear. Herein, we investigated the effects and mechanisms of Fe/Mn-MBCs prepared via one-pot pyrolysis of pig manure impregnated with ferric nitrate and potassium permanganate on ARG abundance and risk using soil microcosms combined with bacterial conjugation and natural transformation assays. While pristine biochar increased total ARG relative abundance, Fe/Mn-MBCs bearing nano-sized oxides (e.g., Fe3O4, Mn3O4, MnO2) decreased it by 23.17%-44.54%, and high-risk ARGs (aadE, floR) by 28.73%-50.19%, demonstrating the feasibility for mitigating soil ARG pollution and health risks. Mechanistically, Fe/Mn-MBCs reshaped the bacterial community by enriching Fe/Mn-redox bacteria (e.g., Terrimonas, Stenotrophobacter), while strengthening dispersal limitation of potential ARG hosts (e.g., Actinobacteria, Firmicutes). Fe/Mn-MBCs also suppressed horizontal gene transfer (HGT), as evidenced by the decreased abundances of mobile genetic elements (intI1, tn916, tnpA) by 10.60%-40.80%. This was further confirmed by the decreased frequencies of conjugation and transformation. Fe/Mn-MBCs suppressed intracellular ARG conjugations by reducing cell membrane permeability, ATP synthesis, and bacterial motility, while inhibiting extracellular ARGs (eARGs) transformation via plasmid adsorption and reduced eARG availability. These findings advance mechanistic understanding of Fe/Mn-MBCs in mitigating soil ARG pollution through potential ARG host reduction and HGT suppression, and guide the rational design of functionalized biochars as an in‑situ remediation strategy against antimicrobial resistance in agroecosystems.

The study presents an investigation into the concentrations of polycyclic aromatic hydrocarbons (PAHs) and phenanthrene derivatives in bark-and-wood wastes (BWW) from sawmills following long-term storage (70 years), as well as an identification of the factors influencing their accumulation and toxicity. Elevated levels of PAHs and their derivatives were detected in the BWW profiles. Low-molecular-weight (LMW) PAHs exhibited a relatively uniform vertical distribution throughout the profiles of both cores. In deeper layers (below 12 m), the concentrations of high-molecular-weight (HMW) PAHs and their derivatives increased sharply. This accumulation is attributed to pedogenic processes occurring during waste decomposition under conditions of elevated temperature and humidity. Additionally, an inverse relationship was identified in the accumulation of PAHs and their derivatives in lower BWW layers. The elevated concentrations of HMW PAHs and derivatives observed in the upper section of Core 1 are likely associated with fire-related phenomena characteristic of BWW landfills. PCA analysis revealed a significant correlation between the accumulation of PAHs and derivatives and the pH and moisture content of the waste. Specifically, higher concentrations of the target compounds were detected under conditions of high moisture content and neutral pH. The lower layers of the BWW exhibited high toxicity; notably in Core 1, the total toxic equivalency concentration (TEQ) exceeded the maximum permissible concentration (MPC) of benzo[a]pyrene for soils by up to a factor of nine. Ecological risk assessments indicated the upper BWW layers pose a low risk to living organisms and natural ecosystems, whereas the lower layers presented a moderate risk.

In situ biomethanation upgrades biogas by converting CO2 and externally supplied H2 into CH4 directly within anaerobic digesters. However, elevated H2 partial pressure can disrupt syntrophic interactions and impair anaerobic digestion (AD). Microbial adaptation, particularly within archaeal communities, may mitigate these effects. This study assessed how prior H2 exposure influences organic matter conversion under increasing organic loading rate (OLR). Two 3-L mesophilic continuous stirred-tank reactors were operated either in in situ biomethanation mode (i.e., H2-supplied AD), with H2 supplied at 2 NmL·min-1, or as AD without H2 addition. Using an H2-adapted inoculum, the OLR was increased stepwise from 2.5 to 6.0 gVS·L-1·d-1, while maintaining the hydraulic retention time (∼30 days). The maximum CH4 production rate at the highest OLR applied (6.0gVS·L-1·d-1) increased by 351 NmL CH4·L-1·d-1 in AD, while it was doubled in the in situ biomethanation reactor (733 NmL CH4·L-1·d-1). Similarly, AD and in situ biomethanation produced 57 % and 76 % of the theoretical CH4 expected from the additional organic matter added when increasing the OLR, and therefore a higher accumulation of volatile fatty acids was observed in AD. Despite the increasing OLR, H2 conversion remained above 98 % throughout the experiment under in situ biomethanation. H2 addition led to a more balanced archaeal community, with similar abundances between hydrogenotrophic methanogens and Methanosarcina sp., while in AD, Methanosarcina sp. largely dominated the archaeal community with the increasing OLR. Whereas bacterial community trajectories remained broadly similar between reactors. Overall, H2-adapted in situ biomethanation enhanced CH4-oriented carbon conversion while impeding metabolic imbalance.

Low-temperature (15 °C) municipal wastewater treatment is constrained by electron-donor deficiency and slowed microbial kinetics. Within an integrated floc-biofilm sequencing batch reactor under anaerobic-aerobic-anoxic mode, this study investigated the combined effects of sludge fermentation products (SFP) addition and hydraulic retention time (HRT) modulation on total inorganic nitrogen (TIN) removal. A 2 × 2 factorial experiment with two-way analysis of variance revealed that, under conventional HRT, SFP addition resulted in a non-significant decrease in TIN removal from 68.2% to 61.0% (F = 0.08, P = 0.783). Conversely, HRT extension interacted positively with SFP (F = 92.85, P < 0.001), eliminating this suppression and raising TIN removal to 80.5%. Long-term operation achieved 81.5% TIN removal and a 31.0% aerobic nitrite accumulation rate. SFP served as an electron donor for denitrification, while nitrite-oxidizing bacteria showed greater sensitivity to SFP than ammonia-oxidizing bacteria. HRT extension (aerobic: 6 to 7 h, anoxic: 8 to 9 h) alleviated cold-induced kinetic limitations and enhanced substrate conversion. Crucially, polyhydroxyalkanoate (PHA)-associated endogenous carbon metabolism was enhanced after HRT extension, with PHA peak, storage, and consumption increasing 2.7-, 3.1-, and 3.2-fold, respectively, relative to baseline (no SFP, no HRT extension). Furthermore, community analysis revealed spatial niche differentiation. The biofilm was enriched in cold-tolerant Candidatus Brocadia fulgida associated with anammox, while heterotrophic denitrification and carbon metabolism predominated in the flocs. These results support a carbon-kinetic dual-factor strategy for advanced nitrogen removal in cold-region municipal wastewater treatment.

Although partial nitritation and anammox (PN/AMX) has been successfully established for treating sidestream wastewater, low NH4+-N concentration and suppression of nitrite oxidizing bacteria (NOB) are challenges in mainstream wastewater. This study reports the emergence and assessment of PN/AMX-associated activity in single-stage high-rate nitrifying packed bed biofilm reactor (PBBR), operated for ∼ 400 days, with an influent NH4+-N concentration close to mainstream, i.e., 100 mg-N/L, under relatively low hydraulic retention time (∼1.6 h). With gradually increasing volumetric ammonium loading rates (V-ALR) from 300 to 1500 g-N/m3·d during initial stages of operation, dominance of ammonium oxidizing bacteria (AOB) and NOB was achieved, offering complete nitrification. During prolonged operation at V-ALR of 1500 g-N/m3·d, a gradual reduction in dissolved oxygen (DO) saturation in the bulk liquid (at constant aeration rates) to below 45% coincided with NO2--N accumulation, reduced NO3--N formation, and emergence of inferred PN/AMX associated activity. Under DO limited conditions, a peak inferred AMX activity of around 30 mg-N/L·h was observed, with an estimated activity-based doubling time of ∼ 28 d. Microbial community analysis was consistent with these observations, wherein significant reduction in abundance of NOB (Nitrospira) was observed during AMX phase (4.6%) as compared to high-nitrification stage (59.8%). Also, during the AMX phase, the reactor was enriched with Candidatus Brocadia genus with a relative abundance of 20.9%. While these preliminary observations suggest the potential of PBBR for high-rate PN/AMX associated activity, further systematic investigations and validation using real wastewater are needed.

Simultaneous partial nitrification, anammox and denitrification (SNAD) couples multiple pathways for nitrogen removal from wastewater with limited organic carbon. However, competition among functional guilds for O2, NO2[-], organic carbon and space makes it difficult to infer the actual role of carriers from total nitrogen removal or microbial abundance. This review follows a conceptual chain from carrier properties and the carrier-microbe interface to local microenvironments, niche partitioning and nitrogen flux allocation. It examines how carrier architecture and surface chemistry, extracellular polymeric substances (EPS), substrate transport, signal bioavailability and redox activity influence biomass retention and pathway competition. Particular attention is given to NO2[-] supply and consumption, the competing fates of NO3- through complete denitrification, partial denitrification-anammox (PdNA) or dissimilatory nitrate reduction to ammonium (DNRA), and changes in the anammox contribution under different operating conditions. A claim-specific E1-E3 analytical evidence framework distinguishes performance associations, mechanistic support, and pathway-resolved or controlled-intervention evidence, while defining the interpretive scales of nitrogen balance estimates, ex situ 15N potential activity and in situ reactor fluxes. Current evidence consistently supports carrier-mediated effects on biomass retention and local mass transfer, whereas signalling regulation, direct extracellular electron transfer and carrier-specific causality require targeted validation. Biofilm ageing, interfacial drift and reactivation after maintenance affect the long-term preservation of target functions, while material loss and life-cycle burdens constrain engineering value. We therefore propose an evidence chain linking material properties, local processes, target nitrogen fluxes and long-term operating performance as the basis for evaluating functional carriers in SNAD.

Microalgal-bacterial granular sludge (MBGS) is a promising low-carbon wastewater treatment technology, but its application is limited by slow start-up. Here, the effects of magnetite nanoparticles (Fe3O4 NPs) on MBGS formation were evaluated in four parallel photo-sequencing batch reactors (PSBRs). The reactors were operated without NPs or supplemented with 10, 50, and 100 mg/L Fe3O4 NPs. Fe3O4 NP addition markedly accelerated granulation, with the >50% granulation threshold reached by day 15 at 50 and 100 mg/L, compared with day 30 in the control and 10 mg/L reactors. This improvement was accompanied by better settling performance, earlier extracellular polymeric substance enrichment, a higher protein-to-polysaccharide ratio, and faster establishment of a tightly bound, protein-rich matrix. By day 45, granulation ratio increased from 73% in the control to 77%, 81%, and 84% in the 10, 50, and 100 mg/L reactors, respectively. Although Fe3O4 NPs delayed pigment accumulation during start-up, final chlorophyll and carotenoid contents were higher in the NP-amended reactors, and microalgal nutrient assimilation was not impaired. Phosphorus removal peaked at 50 mg/L Fe3O4 NPs (95.6%), whereas 100 mg/L provided no additional overall benefit. Microbial community analysis showed enrichment of polymer-producing, structurally supportive genera, including Nakamurella, Micropruina, and Streptomyces, together with higher abundances of phosphorus-associated taxa in NP-amended reactors. Overall, Fe3O4 NPs accelerated MBGS start-up by promoting structural maturation ahead of phototrophic stabilization, with 50 mg/L recommended as the optimal dosage under the tested conditions because it shortened the key granulation phase while achieving the highest phosphate removal.

Ciprofloxacin usually exists at low concentration in surface water and wastewater. In this research, the nitrogen removal, enzymatic activity, antioxidant response, microbial succession, functional gene and antibiotic resistance genes (ARGs) of sequencing batch reactor were investigated under long-term exposure of 100 μg/L ciprofloxacin. The NH4[+]-N removal efficiency almost unchanged during 188-day operation. However, the ammonia-oxidizing rate, nitrite-oxidizing rate, nitrate-reducing rate and nitrite-reducing rate decreased by 17.34 %, 18.38 %, 24.98 % and 38.81 % on day 188 by comparison with 0 µg/L ciprofloxacin, respectively. Similarly, the activities of ammonia monooxygenase, nitrite oxidoreductase, nitrate reductase and nitrite reductase decreased by 25.76 %, 27.79 %, 30.65 % and 39.81 %, respectively. The increase of antioxidant enzymatic activity under long-term ciprofloxacin stress eliminated excess reactive oxygen species to alleviate oxidative damage. The relative abundances of Nitrosomonas, Nitrosospira, Nitrobacter and Nitrospina decreased with the increase of operation time. The relative abundances of nitrogen-removal key genes (e.g., amoA, nxrA, narG and nosZ) decreased with the increase of operation time, as well as the key enzymes in TCA cycle with their encoding genes. The total abundance of the top 30 ARGs increased by 7.57-fold by comparison with 0 µg/L ciprofloxacin, especially for efflux pump genes. The enrichment of ARG-encoded efflux pumps and antioxidant defense competed for the limited electrons and ATP, which led to an energy/electron trade-off with nitrogen metabolism. The present results are helpful to deeply understand the linkage among the nitrogen removal, microbial community and resistance genes under long-term exposure of low antibiotic concentration.

Corn stalk (CS), a renewable and sustainable agricultural waste, was used to produce electrode materials for supercapacitors. CS was first pre-carbonized at 600°C under nitrogen and then activated with potassium hydroxide (KOH) at biochar:KOH mass ratios of 1:1‒1:4 and temperatures of 600-900°C. The activated biochars were characterized by Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller surface area (BET), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-Ray diffraction (XRD), and Raman spectroscopy. The materials exhibited micropore-rich hierarchical porous structures with specific surface areas ranging from 1178‒2998 m[2] g[-1] and ID/IG ratios ranged in 0.77 to 1.11. Eight different electrodes were prepared using the biochars, carbon black, and polyvinylidene fluoride (PVDF) at a weight ratio of 8:1:1. Electrochemical performance was evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectrometry (EIS) techniques in three- and two-electrode systems (reference electrode: Ag/AgCl, counter electrode:Pt. electrolyte: 6 M KOH in three-electrode configuration). CS-800-K2, activated at 800°C with biochar:KOH mass ratio of 1:2, exhibited the best electrochemical performance, with a specific capacitance of 220F g[-1] at 0.5 A g[-1] in three-electrode system. The electrode retained 105% of its capacitance after 7500 cycles. In a symmetric two-electrode configuration, CS-800-K2 delivered 124F g[-1]at 0.5 A g[-1], with a maximum energy density of 4 Wh kg[-][1] and a maximum power density of 553 W kg[-][1]. These results demonstrate the potential of corn-stalk-derived activated biochar as a low-cost, sustainable electrode material for supercapacitors.

Tire wear particles (TWPs) represent a major source of environmental microplastics, yet how ultraviolet (UV) aging influences their effects on the transfer of antibiotic resistance genes (ARGs) remains unclear. Here, the promoting effects and underlying mechanisms of UV-aged TWPs and their leachate on bacterial conjugative transfer were investigated. Aging significantly increased the specific surface area and oxygen-containing functional groups of TWPs, and promoted the release of heavy metal ions and organic additives into leachate. In conjugation assays, 60-day-aged TWPs enhanced the transfer frequency of plasmid RP4 by 15.3-fold; whereas the corresponding leachate alone caused a 62.0-fold increase. Mechanistically, aged TWPs acted primarily as a physical oxidative stressor, promoting conjugative transfer through reactive oxygen species (ROS) generation and disruption of cell membrane integrity. Aged leachate acted mainly as a chemical signaling stressor, inducing biofilm formation and collective behavioral responses that created a protective microenvironment conducive to plasmid exchange, although they also contributed to oxidative stress. Combined exposure further produced a response greater than that of either pathway alone, establishing a physicochemical dual-stress framework that drives ARGs transfer. Collectively, these findings suggest that environmental aging critically shapes the ecological risks of microplastics, positioning aged TWPs as potential vectors for ARGs dissemination and underscoring the need to consider both particle-associated and leachate-mediated pathways in future risk assessments.

The anaerobic ammonium oxidation (anammox) process has received extensive attention because of its low energy consumption and high nitrogen removal efficiency. Nevertheless, its long start-up period limits practical application. In this study, a microalgae-bacteria symbiotic system (ABSS) based on Chlorella vulgaris (C. vulgaris) was established to investigate its effects on anammox start-up and nitrogen and phosphorus removal. The introduction of C. vulgaris shortened the start-up time from 68 to 46 days, corresponding to a 32 % reduction. After 210 days of operation, the nitrogen removal rate (NRR) and phosphorus removal rate (PRR) in the microalgae-bacteria symbiotic reactor (RAM) were 21 % and 25 % higher than those in the control reactor (RA), respectively. The concentration of extracellular polymeric substances (EPS) derived from C. vulgaris, as quantified via total organic carbon measurement, was 297.73 ± 8.55 mg/L. Spectroscopic analyses suggested the presence of humic-like substances and quinone-related structures in the EPS, indicating a potential role in electron transfer. At 100 mg/L, EPS increased hydrazine dehydrogenase (HDH) activity by 49 % relative to the control group. After CoQ extraction, EPS restored HDH activity more effectively than exogenous coenzyme Q (CoQ). Metagenomic analysis showed higher abundances of genes associated with photosynthesis, carbon fixation, and nitrogen metabolism. These findings imply that EPS-mediated electron transfer and strengthened HDH activity may have contributed to the establishment of anammox activity and the shortened start-up period. Overall, this study highlights microalgal integration as a potential strategy for accelerating anammox startup and improving simultaneous nitrogen and phosphorus removal.

Tetracycline (TC) threatens water quality and health, but photoaging-induced shifts in adsorption pathway contributions and functional group responses remain unclear at the atomic scale. Fe-modified straw biochar (FeBC) was synthesized at 400/800 °C, and the effects of pyrolysis temperature and photoaging on TC adsorption were investigated via batch adsorption, 2D-FTIR-COS, chemical inhibition, and DFT calculations. Pyrolysis at 800 °C produced an aromatic micro-mesoporous network (SBET 557.29 m[2]·g[-1]), while FeCl3 loading yielded crystalline FeO/γ-Fe2O3, magnetic responsiveness (10.00 emu·g[-1]), and abundant complexation sites. FeBC800 showed a maximum TC adsorption capacity of 123.66 mg·g[-1] and maintained > 97.8% removal over five cycles and in real waters. Quantitative analysis revealed that non-electrostatic and non-complexation pathways, mainly pore filling, π-π, and hydrogen bonding, contributed 73.87%, while surface complexation contributed 20.01% (24.75 mg·g[-1]). 2D-FTIR-COS identified Fe-O as the preferential adsorption site, and DFT confirmed strong electronic coupling (Fe-O 1.906 Å, Eads - 3.34 eV). Photoaging hydroxylated Fe, lengthened Fe-O to 2.060 Å, weakened Eads to - 0.96 eV, and reduced surface complexation from 20.01% to 4.17% (24.75 to 4.71 mg·g[-1]), shifting the dominant pathway to pore confinement and π-π interactions. Aged FeBC800 still retained 91.5% capacity, demonstrating environmental robustness. This work provides a quantitative multi-scale framework for predicting photoaging-induced pathway shifts and designing robust Fe-modified biochars.

Overflow metabolism is traditionally defined as the production of low-energy-yield metabolites despite the availability of more energy-efficient pathways, exemplified by acetate secretion in Escherichia coli, ethanol production in yeast, and lactate formation in mammalian cells. Despite extensive study, the mechanisms underlying overflow metabolism remain incompletely understood. Increasing evidence further demonstrates that overflow-like metabolism is not restricted to carbon excess but also occurs under nutrient limitation, environmental stress, recombinant protein expression, and within microbial communities, indicating that its physiological significance extends far beyond the classical paradigm. Here, we review these diverse manifestations, evaluate the underlying mechanisms of overflow metabolism, and propose adopting a separable, reversible Michaelis-Menten formulation as a unifying conceptual framework. This framework integrates catalytic capacity, substrate saturation, product inhibition, and thermodynamic driving forces into a cohesive explanation. Within this framework, overflow metabolism emerges when substrate influx exceeds the processing capacity of more energy-efficient pathways, resulting in flux redistribution toward alternative routes with distinct energetic, kinetic, and/or proteome-allocation characteristics. By bridging enzyme kinetics, resource allocation, thermodynamics, and microbial ecology, this framework may unify diverse forms of overflow metabolism and provide a predictive foundation for engineering this metabolic behavior in microbial systems.

Anaerobic digestion produces methane-rich biogas and ammonium-rich digestate, but their joint conversion into single-cell protein (SCP) requires coordinated carbon and nitrogen utilisation. Here, a methane-fed mixed consortium was operated in a membrane biofilm reactor to determine how acetate regulates carbon-nitrogen coordination under ammonium stress. Ammonium addition impaired nitrogen conversion and protein enrichment without eliminating methylotrophs. Acetate restored these functions, increasing protein content to 61.25 % and the apparent N-based SCP yield from 0.34 to 1.46 g SCP/g N. Nitrogen balances showed greater incorporation of inorganic nitrogen into cellular organic nitrogen with acetate, consistent with the increased metagenomic potential for the glyoxylate shunt and ammonium assimilation. Excess acetate, however, promoted soluble microbial products and extracellular polymeric substances, lowering the apparent carbon-based SCP yield. These findings suggest that acetate improves nitrogen incorporation and protein production in a methane-fed mixed consortium while methane utilisation remains active. Controlled acetate retention in anaerobic digestate may therefore support the joint recovery of waste-derived carbon and nitrogen as microbial protein.

Composting recycles livestock manure, but temporally distinct ammonia, nitrous oxide and methane emissions can obscure trade-offs between nitrogen conservation and climate mitigation. We evaluated staged supplementation with waste-based lactic acid fermentation broth (LA) during 42-d forced-aeration rotary-drum composting of swine manure and maize straw, using three parallel reactors per treatment and equal-mass water addition (WA) as the control. LA showed a short initial heating/decomposition lag followed by thermophilic and carbon-transformation catch-up. Reactor-mean ammonia release during temperature-defined days 2-6 was 49.9% lower; the sampled peak shifted from day 3 to day 5 and was 17.3% lower. Later compensation limited the day-42 mean difference to 7.8%, indicating early-window attenuation and redistribution. Observed cumulative means of nitrous oxide and methane were 41.5% and 37.3% lower, respectively, producing a 38.5% lower direct non-CO2 greenhouse-gas mean. Lower early pH was consistent with a lower estimated free-ammonia fraction and temporary maintenance of an ammoniacal pool. Higher early nosZ/(nirK + nirS) and nosZ/nirK ratios indicated greater annotated terminal nitrous-oxide-reduction potential relative to nitrite-reduction potential. After day 21, methane approached zero despite a higher sampled methane peak under LA, as late carbon dioxide release weakened and mcrA, mcrB and mcrG abundances remained low. These DNA profiles represent functional potential rather than gene activity. Both germination index (GI) means exceeded the 70% criterion by day 7; late temperature, carbon dioxide, total organic carbon (TOC) and humic-like dissolved organic matter (DOM) supported progressive stabilization. Strong early ammonia attenuation is promising for recurrent-feed thermophilic semi-continuous systems with captured exhaust, based on batch results.