Bacterial community changes and antibiotic resistance gene quantification in microbial electrolysis cells during long-term sulfamethoxazole treatment

Enhancing tetracycline removal: Performance and mechanisms of interspecies electron transfer in microbial consortia

With the widespread application of antibiotics in aquaculture, antibiotic contamination of manure has become a serious concern. Interspecies electron transfer between microorganisms plays a crucial role in antibiotic biodegradation. This study investigated the impact and mechanism of electron transfer on tetracycline degradation in microbial electrochemical systems. The results demonstrated that at an initial tetracycline concentration of 5 mg/L, the closed-circuit (CC) group achieved a removal rate exceeding 91.98 % within 4 d, which was 2.71 times higher than that of the open-circuit (OC) group. The electron transfer capacity of the CC group was also significantly greater than that of the OC group. Microbial community analysis identified Serratia, Petrimonas, Pseudochrobactrum, and Sphingobacterium as the key potential tetracycline-degrading genera. Additionally, catalase activity in the CC group was significantly enhanced, reaching up to four times that observed in the OC group. Molecular docking further confirmed the strong affinity between catalase and tetracycline, suggesting that catalase plays a significant role in tetracycline degradation. This study offers both theoretical insights and technical support for enhancing the microbial treatment efficiency of organic pollutants.

Efficient removal of enrofloxacin in swine wastewater using eukaryotic-bacterial symbiotic membraneless bioelectrochemical system

A eukaryotic-bacterial symbiotic membraneless bioelectrochemical system (EBES) reactor with eukaryotic-bacteria symbiotic cathode was developed to treat swine wastewater containing enrofloxacin (ENR), which had high performance at ENR tolerance and operational stability. With ENR concentrations shifting from 2 to 50 mg/L, the removal efficiencies of ENR, chemical oxygen demand (COD) and NH4+-N always were higher than 95 %, and the maximum power output (≥343 mW/m3) could be achieved. At 20 mg/L ENR, the removal efficiencies of ENR, COD and NH4+-N respectively reached to 99.4 ± 0.1 %, 98.5 % ± 0.1 %, and 96.3 % ± 0.5 %, corresponding to the open circuit voltage and maximum power density (Pmax) of EBES were 851 mV and 455 mW/m3. The community analyses showed that bacteria (Comamonas, Rhodobacter, Rhodococcus, and Vermiphilaceae et al.), algae (Chlorella) and fungi (Rozellomycota, Trebouxiophyceae, Exophiala, and Aspergillus et al.) at genus level were the dominate populations in the EBES, and their abundance increased with ENR concentration, suggesting they played key roles to remove ENR and another nutrient element. The low relative abundances (1.9 ×10-7 to 1.1 ×10-5 copies/g) of aac (6')-ib-cr, qnrA, qnrD, qnrS, and gyrA in effluent revealed that the present EBES reactor had superior capabilities in controlling antibiotic-resistance genes and antibiotic-resistant bacteria. Our trial experiments provided a novel way for antibiotic livestock wastewater treatment.

Enhanced methanogenesis and efficient ciprofloxacin degradation via nZVI@LDH in an electricity-driven anaerobic bioreactor: A biotic-abiotic hybrid system for ROS regulation and ARGs mitigation

The escalating presence of antibiotic contaminants in wastewater presents substantial environmental and public health challenges, primarily due to their role in the proliferation of antibiotic resistance genes (ARGs). This study examines the effectiveness of a hybrid system integrating nano zerovalent iron (nZVI) and layered double hydroxides (LDH) in treating wastewater contaminated with ciprofloxacin (CIP). Reactor experiments revealed that incorporating nZVI@LDH mitigated the shock caused by CIP while sustaining a methane production rate that was 116 % higher than that of the control group. Furthermore, there was a 50 % increase in CIP removal efficiency. Notably, there was a significant enrichment of hydrogenotrophic methanogens, such as Methanobacterium and Methanolinea, in the nZVI@LDH-enhanced reactors. Additionally, the levels of reactive oxygen species decreased by 50 %, from 11,813 ± 1230 to 4525 ± 1030 counts/s, and the abundance of ARGs declined by 75-88 % compared to the control reactors. An external electric field further promoted electron transfer, boosting the relative abundance of electrochemically active bacteria, with Proteobacteria comprising up to 40 % of the microbial community in the 1 V + nZVI@LDH reactor. This hybrid system demonstrates significant efficacy in degrading CIP and decreasing ARGs generation, underscoring its potential as a sustainable strategy for managing antibiotic-laden wastewater.

Enhanced activity of mixed-culture electroactive biofilms and sulfamethoxazole removal efficiency by adding N-acyl-homoserine lactones in bio-electrochemical system

The addition of exogenous quorum sensing signaling molecules significantly enhanced the degradation efficiency of antibiotics, such as chloramphenicol in bio-electrochemical systems (BESs). However, the effects and mechanisms by which AHLs addition in BES facilitated the removal of sulfamethoxazole (SMX) remained inadequately explored. This study systematically compared the electrochemical performance and SMX removal efficiency in BES under two conditions: with and without the addition of N-acyl-homoserine lactones (AHLs) signaling molecules. In comparison to the control group, the AHL-treated group exhibited an increase in maximum output voltage from 340 to 489.67 mV, alongside a notable enhancement in SMX removal efficiency over 120 h ranging from 14.65% to 15.76%. Analyses of the live and dead cells and extracellular polymeric substances (EPS) composition revealed that following AHLs addition, both the ratio of live to dead cells and protein content within EPS increased by 12.66% and 74.37%, respectively. Furthermore, microbial community structure analysis indicated that after AHLs supplementation, there was a marked increase in the abundance of electroactive microorganisms as well as antibiotic-degrading and nitrogen-removing bacteria. Notably, Klebsiella - characterised by its electroactivity along with antibiotic degradation and nitrogen removal capabilities - exhibited a relative abundance reaching 56.84% in AHL, reflecting an increase of 28.31% compared to Blank; additionally, electroactive bacteria Dysgonomonas showed a relative abundance rise of 2.49%. Collectively, these findings suggested that enhancements in SMX removal efficiency upon AHLs addition were primarily driven by improvements in electrochemical performance coupled with alterations in microbial community structure.Highlights The electrochemical performance in AHL was improved compared with Blank.The protein content in extracellular polymeric substances increased by 74.37% in AHL.The removal efficiency of sulfamethoxazole in 120 h increased by up to 15.76% in AHL.The abundance of functional bacteria such as Klebsiella increased in AHL.

Recent advancements in antibiotics removal by bio-electrochemical systems (BESs): From mechanisms to application of emerging combined systems

Recent advancements in bio-electrochemical systems (BESs) for antibiotic removal are receiving great attentions due to the electro-active bacteria on the electrode that could elevate the removal efficiency. Enhanced detoxification performance of BESs compared to the traditional biological processes indicates the great potential serving as a sustainable alternative or a pre-/post-processing unit to improve the performance of biological processes. However, the successfully application of BESs to antibiotic-polluted water remediation requires a deeper discussion on their operational performance and emerging coupled systems. In order to address BESs as a practical option for antibiotic removal, we deeply analyze the detoxification mechanism of antibiotic treatment by BESs, involving BES fundamentals, extracellular electron transfer and degradation pathways via functional enzymes of microorganisms, followed by systematic evaluations of the operational conditions. Furthermore, the recently-emerged BESs combined with other techniques for practical applications has been summarized and emphasized. This review further directions the current limitations such as the potential risk of antibiotic resistance genes, etc., and prospects for the attenuation of antibiotics via BESs related techniques, promoting the development of practical application.

Sulfamethoxazole removal in nitrifying membrane aerated biofilms: Physiological responses and antibiotic resistance genes

Efficient removal of ammonia nitrogen and sulfamethoxazole (SMX) from wastewater has become increasingly critical due to their detrimental effects on aquatic ecosystems and public health. This study aimed to investigate the nitrogen transformation and SMX removal in a membrane aerated biofilm reactor (MABR) under different SMX concentrations (0-200 μg L-1) with a nitrifying membrane bioreactor (MBR) as a control. Results suggested that SMX removal in MABR was better than that of MBR with SMX addition (50-200 μg L-1). Membrane aerated biofilms tended to secrete more extracellular polymeric substances (EPS) and generate less antioxidant enzymes in response to SMX stress when compared with nitrifying sludge in MBR. Metagenomic analysis indicated that distinct succession of microbial community was observed in both systems after SMX addition, and the relative abundance of nitrifying bacteria (Nitrosomonas, Nitrospira, and Nitrobacter) evidently decreased under SMX concentration of 200 μg L-1. The proliferation of predominant antibiotic resistance gene (ARG) sul2 was suppressed more obviously in MABR than that in MBR. Thus, this study provided extensive insights into the advantages of nitrifying MABR in simultaneous removal of ammonium and antibiotics with less risk of associated ARGs spread.

Sulfamethoxazole removal and ammonium conversion in microalgae consortium: Physiological responses and microbial community changes

Microalgae (Mychonastes sp.) consortium was investigated for nutrient and antibiotics removal and its responses to varying sulfamethoxazole (SMX) concentrations (0-1000 μg/L) in ammonia-rich wastewater. The results showed that the introduction of SMX (100-1000 μg/L) slightly improved ammonium nitrogen removal efficiency instead of inhibition. Swift SMX degradation was observed across all SMX-treated systems, with the highest SMX removal efficiency (96 %) at an SMX concentration of 100 μg/L. Biodegradation remained the dominant SMX removal mechanism, contributing 78 % of SMX removal at an SMX concentration of 800 μg/L, while adsorption and photolysis played minor roles. Addition of SMX augmented biomass and lipid productivity, but decreased chlorophyll contents in the microalgae consortium. Furthermore, extracellular polymeric substance (EPS) production correlated positively with SMX input concentration, with the microalgae consortium exposed to 800 μg/L SMX displaying the most pronounced stimulation of protein production (51.5 ± 2.0 mg/g DCW) and polysaccharides production (74.8 ± 3.9 mg/g DCW). In response to an increase in SMX concentrations, enzyme activities associated with antioxidant defense, such as superoxide dismutase (SOD), peroxidase (POD) and malondialdehyde (MDA) increased, the catalase (CAT) decreased, indicating an initial defense mechanism. Concurrently, the relative abundance of Mychonastes sp. within the consortium rose from 87 % at 300 μg/L SMX to 99.9 % at 800 μg/L SMX. while Shannon indices of the bacterial community increased from 1.415 to 2.867. This shift inhibited the initially dominant Saprospiraceae bacteria, facilitating the profound increase of adapted Aquimonas. These findings demonstrate the feasibility of the simultaneous removal of antibiotics and nutrients from wastewater with a microalgae consortium system.

A comprehensive review of antibiotic resistance gene contamination in agriculture: Challenges and AI-driven solutions

Since their discovery, the prolonged and widespread use of antibiotics in veterinary and agricultural production has led to numerous problems, particularly the emergence and spread of antibiotic-resistant bacteria (ARB). In addition, other anthropogenic factors accelerate the horizontal transfer of antibiotic resistance genes (ARGs) and amplify their impact. In agricultural environments, animals, manure, and wastewater are the vectors of ARGs that facilitate their spread to the environment and humans via animal products, water, and other environmental pathways. Therefore, this review comprehensively analyzed the current status, removal methods, and future directions of ARGs on farms. This article 1) investigates the origins of ARGs on farms, the pathways and mechanisms of their spread to surrounding environments, and various strategies to mitigate their spread; 2) determines the multiple factors influencing the abundance of ARGs on farms, the pathways through which ARGs spread from farms to the environment, and the effects and mechanisms of non-antibiotic factors on the spread of ARGs; 3) explores methods for controlling ARGs in farm wastes; and 4) provides a comprehensive summary and integration of research across various fields, proposing that in modern smart farms, emerging technologies can be integrated through artificial intelligence to control or even eliminate ARGs. Moreover, challenges and future research directions for controlling ARGs on farms are suggested.

Integrated bio-electrochemical approach to Norfloxacin (NFX) degradation: Efficacy, degradation mechanisms, and toxicological insights

Norfloxacin (NFX), a widely used fluoroquinolone antibiotic, poses significant environmental concerns due to its persistence in ecosystems and its potential to foster antibiotic resistance. This study explores the degradation of NFX using a bio-electrochemical system (BES) facilitated by Bacillus subtilis isolated from animal waste sludge. Experimental parameters were optimized to maximize removal efficiency, with the optimal conditions determined as an NFX concentration of 200 mg/L, pH 7, and an applied potential of 1.2 V. The degradation pathway was elucidated through the identification of intermediate products, ultimately leading to the complete mineralization of NFX. To assess the environmental impact of BES-treated water, a series of eco-toxicity assays were conducted. Microbial diversity analysis revealed that soil exposed to BES-treated water maintained a balanced microbial community, contrasting with the disruptions observed in soils exposed to untreated NFX-contaminated water. Phytotoxicity tests, earthworm toxicity assay, and Artemia hatchability & lethality assays further confirmed the reduced toxicity of the BES-treated water. These findings highlight the efficacy of BES in the degradation of NFX, demonstrating its potential as a sustainable strategy for the remediation of antibiotic-contaminated environments and the mitigation of associated ecological risks.

The effect of extracellular polymeric substances on the distribution and transmission of antibiotic resistance genes treating antibiotic wastewater via microbial electrolysis cells

Microbial electrolysis cells (MEC) have emerged as a prominent technology for the treatment of antibiotics-containing wastewater in recent years. However, there remains a dearth of comprehensive exploration regarding the influence of extracellular polymers substances (EPS) on the distribution and transmission of antibiotic resistance genes (ARGs) in MEC. In this study, we quantified the distribution of ARGs in MEC by Fluorescence quantitative polymerase chain reaction and explored with emphasis on impact of EPS component on ARGs transmission at under different concentrations of roxithromycin. Results showed that the absolute abundance of ARGs in the electrode biofilm was 1-2 orders of magnitude higher than that in the anolyte. Specifically, EPS-associated ARGs accounted for 2.31%-11.18% of ARGs in electrode biofilm. The presence of elevated roxithromycin concentration led to electroactive microorganisms (Geobacter and Geothrix) as potential hosts of ARGs. In addition, both protein and polysaccharide content in the electrode biofilm increased with increasing roxithromycin concentration and showed positive correlations with EPS-associated ARGs. Fluorescence quenching experiments further elucidated that tryptophan and tyrosine residues in EPS could bind to ARGs effectively, contributing the hindering the ARGs transmission between hosts. Therefore, increased EPS content within electrode biofilm could reduce the concentration of ARGs present in anolyte while also influencing ARGs distribution throughout MEC. This study provides valuable insights into the distribution of ARGs in MEC systems and the role of EPS in regulating ARGs migration.

Bioelectrochemical remediation of soil antibiotic and antibiotic resistance gene pollution: Key factors and solution strategies

In recent years, owing to the overuse and improper handling of antibiotics, soil antibiotic pollution has become increasingly serious and an environmental issue of global concern. It affects the quality and ecological balance of the soil and allows the spread of antibiotic resistance genes (ARGs), which threatens the health of all people. As a promising soil remediation technology, bioelectrochemical systems (BES) are superior to traditional technologies because of their simple operation, self-sustaining operation, easy control characteristics, and use of the metabolic processes of microorganisms and electrochemical redox reactions. Moreover, they effectively remediate antibiotic contaminants in soil. This review explores the application of BES remediation mechanisms in the treatment of antibiotic contamination in soil in detail. The advantages of BES restoration are highlighted, including the effective removal of antibiotics from the soil and the prevention of the spread of ARGs. Additionally, the critical roles played by microbial communities in the remediation process and the primary parameters influencing the remediation effect of BES were clarified. This study explores several strategies to improve the BES repair efficiency, such as adjusting the reactor structure, improving the electrode materials, applying additives, and using coupling systems. Finally, this review discusses the current limitations and future development prospects, and how to improve its performance and promote its practical applications. In summary, this study aimed to provide a reference for better strategies for BES to effectively remediate soil antibiotic contamination.

A systematic review of antibiotics and antibiotic resistance genes (ARGs) in mariculture wastewater: Antibiotics removal by microalgal-bacterial symbiotic system (MBSS), ARGs characterization on the metagenomic

Antibiotic residues in mariculture wastewater seriously affect the aquatic environment. Antibiotic Resistance Genes (ARGs) produced under antibiotic stress flow through the environment and eventually enter the human body, seriously affecting human health. Microalgal-bacterial symbiotic system (MBSS) can remove antibiotics from mariculture and reduce the flow of ARGs into the environment. This review encapsulates the present scenario of mariculture wastewater, the removal mechanism of MBSS for antibiotics, and the biomolecular information under metagenomic assay. When confronted with antibiotics, there was a notable augmentation in the extracellular polymeric substances (EPS) content within MBSS, along with a concurrent elevation in the proportion of protein (PN) constituents within the EPS, which limits the entry of antibiotics into the cellular interior. Quorum sensing stimulates the microorganisms to produce biological responses (DNA synthesis - for adhesion) through signaling. Oxidative stress promotes gene expression (coupling, conjugation) to enhance horizontal gene transfer (HGT) in MBSS. The microbial community under metagenomic detection is dominated by aerobic bacteria in the bacterial-microalgal system. Compared to aerobic bacteria, anaerobic bacteria had the significant advantage of decreasing the distribution of ARGs. Overall, MBSS exhibits remarkable efficacy in mitigating the challenges posed by antibiotics and resistant genes from mariculture wastewater.

Bio-electrochemical degradation of carbamazepine (CBZ): A comprehensive study on effectiveness, degradation pathway, and toxicological assessment

Recent attention on the detrimental effects of pharmaceutically active compounds (PhACs) in natural water has spurred researchers to develop advanced wastewater treatment methods. Carbamazepine (CBZ), a widely recognized anticonvulsant, has often been a primary focus in numerous studies due to its prevalence and resistance to breaking down. This study aims to explore the effectiveness of a bio-electrochemical system in breaking down CBZ in polluted water and to assess the potential harmful effects of the treated wastewater. The results revealed bio-electro degradation process demonstrated a collaborative effect, achieving the highest CBZ degradation compared to electrodegradation and biodegradation techniques. Notably, a maximum CBZ degradation efficiency of 92.01% was attained using the bio-electrochemical system under specific conditions: Initial CBZ concentration of 60 mg/L, pH level at 7, 0.5% (v/v) inoculum dose, and an applied potential of 10 mV. The degradation pathway established by identifying intermediate products via High-Performance Liquid Chromatography-Mass Spectrometry, revealed the complete breakdown of CBZ without any toxic intermediates or end products. This finding was further validated through in vitro and in vivo toxicity assays, confirming the absence of harmful remnants after the degradation process.

Degradation of sulfamethoxazole and antibiotic resistance genes from surface water in the photocatalyst-loading bionic ecosystems

The behavior and removal of sulfamethoxazole (SMX) and 3 typical corresponding antibiotic resistance genes (ARGs) including sul1, sul2, sul3, and 16S rDNA in surface water were investigated in the photocatalyst-loading bionic ecosystems (PCBEs). Synthesized composite photocatalyst g-C3N4/TiO2 showing higher catalytic activity than Fe/g-C3N4/TiO2 was selected in the PCBEs. Five PCBEs, i.e., A-the control (without bionic grass or photocatalyst), B-bionic grass loaded with 4.12 g/m2 g-C3N4/TiO2, C-bionic grass loaded with 8.25 g/m2 g-C3N4/TiO2, D-bionic grass loaded with 12.37 g/m2 g-C3N4/TiO2, and E-bionic grass loaded with 16.5 g/m2 g-C3N4/TiO2 were constructed and operated in a medium-scale running cyclical flume. SMX could be photolyzed efficiently by g-C3N4/TiO2 with an optimal unit load on the bionic grass of 12.37 g/m2. 3-amino-5-methylisooxazole and p-aminobenzene sulfonamide were selected as main intermediates through the analyses of SMX degradation mechanisms and pathways, and detected in the aqueous phase and bionic grass. The intermediates were higher in the underwater part of the bionic grass than the above-water part. The overall removal of SMX ranged from 31.7 % to 82.3 % in 5 PCBEs, and the removal of sul1and sul2 were 0.2 %- 62.9 % in the aqueous phase and 8.4 %-63.2 % in the sediment. PCBE D might be the best construction when SMX and ARGs' removal was considered comprehensively. Moreover, the microbial structures showed Proteobacteria as the most dominant bacterial species had a relative abundance of 22.2 %-26.6 % and 33.4 %-68.2 % in the aquatic phase and sediment respectively, illustrating that the removal of the antibiotic and ARGs was bound up with the variations of dominant bacteria in the ecosystems. The findings illustrated that ecosystems with bionic grass and photocatalysts could be a promising technology for the removal of typical antibiotics and ARGs from surface water.

Synergetic effects of catalyst-surface dual-electric centers and microbes for efficient removal of ciprofloxacin in water

Antibiotics and antibiotic resistance genes (ARGs) are still a problem in biological treatment. Herein, we propose a synergetic strategy between microbes and dual-electric centers catalysts (CCN/Cu-Al2O3/ceramsite) for Ciprofloxacin (CIP)-contained (5 mg/L) water treatment in an up-flow biological filter. CIP was cleaved into small molecules by the catalyst, bringing a 57.6% removal and reducing 10.5% ARG. The characterization results verified that a Cu-π electrostatic force occurs on the catalyst surface, forming electron-rich areas around Cu and electron-poor areas at the carbon-doped g-C3N4 (CCN) aromatic ring. Thus, the electrons of adsorbed CIP were delocalized and then captured by the adsorbed extracellular polymeric substance at the electron-rich areas. Therefore, the synergetic process weakened the stress of CIP on bacteria and reduced ARG accumulation. It also enriched more electro-active bacteria on the surface of CCN/Cu-Al2O3/ceramsite, promoting the expression of extracellular electron transfer-related genes and reconstructing the energy metabolism mode. This result provides an opportunity for refractory antibiotic treatment in the biological process.

Enzymatic response and antibiotic resistance gene regulation by microbial fuel cells to resist sulfamethoxazole

Microbial fuel cells (MFCs) are a promising and sustainable technology which can generate electricity and treat antibiotic wastewater simultaneously. However, the antibiotic resistance genes (ARGs) induced by antibiotics in MFCs increase risks to ecosystems and human health. In this study, the activities of enzymes and regulation genes related to ARGs in MFCs spiked with sulfamethoxazole (SMX) were evaluated to explore the induction mechanism of ARGs. Under lower doses of SMX (10 mg/L and 20 mg/L SMX in this study), microorganisms tend to up regulate catalase and RpoS regulon to induce sul1, sul3 and intI1. The microorganisms exposed to higher doses of SMX (30 mg/L and 40 mg/L SMX in this study) tend to up regulate superoxide dismutase and SOS response to generate sul2 and sulA. Moreover, the exposure concentrations of SMX had no significant effect on the electricity production of MFCs. This work suggested that the ARGs in MFCs might be inhibited by affecting enzymatic activities and regulatory genes according to the antibiotic concentration without affecting the electricity production.

Enhanced nitrogen removal via biochar-mediated nitrification, denitrification, and electron transfer in constructed wetland microcosms

This study investigated the effect of biochar on real domestic wastewater treatment by constructed wetlands (CWs). To evaluate the role of biochar as a substrate and electron transfer medium on nitrogen transformation, three treatments of CW microcosms were established: conventional substrate (T1), biochar substrate (T2), and biochar-mediated electron transfer (T3). Nitrogen removal increased from 74% in T1 to 77.4% in T2 and 82.1% in T3. Nitrate generation increased in T2 (up to 2 mg/L) but decreased in T3 (lower than 0.8 mg/L), and the nitrification genes (amoA, Hao, and nxrA) in T2 and T3 increased by 132-164% and 129-217%, respectively, compared with T1 (1.56 × 10⁴- 2.34 × 10⁷ copies/g). The nitrifying Nitrosomonas, denitrifying Dechloromonas, and denitrification genes (narL, nirK, norC, and nosZ) in the anode and cathode of T3 were significantly higher than those of the other treatments (increased by 60-fold, 35-fold, and 19-38%). The genus Geobacter, related to electron transfer, increased in T3 (by 48-fold), and stable voltage (~150 mV) and power density (~9 uW/m²) were achieved. These results highlight the biochar-mediated enhancement of nitrogen removal in constructed wetlands via nitrification, denitrification, and electron transfer, and provide a promising approach for enhanced nitrogen removal by constructed wetland technology.

Spatial Distribution and Risk Assessment of Antibiotics in 15 Pharmaceutical Plants in the Pearl River Delta

Pharmaceutical plants are an essential source of antibiotics emitted into the aqueous environment. The monitoring of target antibiotics in pharmaceutical plants through various regions is vital to optimize contaminant release. The occurrence, distribution, removal, and ecological risk of 30 kinds of selected antibiotics in 15 pharmaceutical plants in the Pearl River Delta (PRD) were investigated in this study. Lincomycin (LIN) showed the highest concentration (up to 56,258.3 ng/L) in the pharmaceutical plant influents from Zhongshan city. Norfloxacin (NFX) showed a higher detection frequency than other antibiotics. In addition, the spatial distribution of antibiotics in pharmaceutical plants showed significant differences, with higher concentrations of total antibiotics found in pharmaceutical plant influents in Shenzhen City than those of different regions in PRD. The treatment processes adopted by pharmaceutical plants were commonly ineffective in removing antibiotics, with only 26.7% of antibiotics being effectively removed (average removal greater than 70%), while 55.6% of antibiotics had removal rates of below 60%. The anaerobic/anoxic/oxic (AAO)-membrane bioreactor (MBR) combined process exhibited better treatment performance than the single treatment process. Sulfamethoxazole (SMX), ofloxacin (OFL), erythromycin-H₂O (ETM-H₂O), sulfadiazine (SDZ), sulfamethazine (SMZ), norfloxacin (NFX), and ciprofloxacin (CIP) in pharmaceutical plant effluents posed high or moderate ecological risk and deserve particular attention.

Efficient elimination of nonylphenol and 4-tert-octylphenol by weak electrical stimulated anaerobic microbial processes

The investigation into the degradation of alkylphenol pollutants (APs) has become a hotspot due to their harmful effects on the environment and human health. In this study, microbial electrolysis cells (MECs) were used to degrade nonylphenol (NP) and 4-tert-octylphenol (4-tert-OP). The study found that the degradation rates of NP and 4-tert-OP for a 6-day period were 83.6% and 96.3%, respectively, which were 30.53% and 26.7% higher than those of the group without applied voltage. The double layer area in the degradation of 4-tert-OP was larger than that of NP, and the resistance exhibited by 4-tert-OP (87.47 Ω) in MEC was lower than that of NP (99.42 Ω). Meanwhile, NP had a greater effect on the bioenzyme activity than 4-tert-OP. GC-MS analysis showed that the degradation pathways of both pollutants mainly included oxidation and hydroxylation reactions. Furthermore, the microbial community analysis indicated that the main functional bacteria in NP degradation were Citrobacter, Desulfovibrio and Advenella, and those in 4-tert-OP degradation were Stenotrophomonas, Chryseobacterium, Dokdonella, and the key microbiomes underlying the cooperative relationship. The biotoxicity test indicated that the toxicity of residual substances was significantly reduced. Therefore, the MEC system is efficient and environmentally friendly and has broad application prospects in phenol refractory organics.

Biofilm response and removal via the coupling of visible-light-driven photocatalysis and biodegradation in an environment of sulfamethoxazole and Cr(VI)

The widespread contamination of water systems with antibiotics and heavy metals has gained much attention. Intimately coupled visible -light-responsive photocatalysis and biodegradation (ICPB) provides a novel approach for removing such mixed pollutants. In ICPB, the photocatalysis products are biodegraded by a protected biofilm, leading to the mineralization of refractory organics. In the present study, the ICPB approach exhibited excellent photocatalytic activity and biodegradation, providing up to ∼1.27 times the degradation rate of sulfamethoxazole (SMX) and 1.16 times the Cr(VI) reduction rate of visible-light-induced photocatalysis . Three-dimensional fluorescence analysis demonstrated the synergistic ICPB effects of photocatalysis and biodegradation for removing SMX and reducing Cr(VI). In addition, the toxicity of the SMX intermediates and Cr(VI) in the ICPB process significantly decreased. The use of MoS₂/CoS₂ photocatalyst accelerated the separation of electrons and holes, with•O₂^- and h⁺ attacking SMX and e^- reducing Cr(VI), providing an effective means for enhancing the removal and mineralization of these mixed pollutants via the ICPB technique. The microbial community results demonstrate that bacteria that are conducive to pollutant removal are were enriched by the acclimation and ICPB operation processes, thus significantly improving the performance of the ICPB system.

Bio-electrocatalytic degradation of tetracycline by stainless-steel mesh based molybdenum carbide electrode

In order to treat antibiotic wastewater with high efficiency and low energy consumption, this study proposed the coupling of electrocatalytic degradation and biodegradation, and explored a new modified electrocatalytic material in the coupling system. The stainless-steel mesh based molybdenum carbide (SS-Mo₂C) was prepared by a low-cost impregnation method and showed superior electrocatalytic degradation ability for tetracycline (TC) when used as the anode in the electrocatalytic system. The degradation rate of TC with SS-Mo₂C anode was 17 times higher than that of stainless-steel (SS) anode, and TC removal efficiency was 77% higher than that of SS anode. The electrocatalytic system prior to the biological reactor was proven to be the optimal coupling method. The external coupling system achieved a significantly higher TC removal (87.0%) than that of the internal coupling system (65.3%) and SS-Mo₂C showed an excellent repeatable and stable performance. The fewer and smaller molecular weight intermediates products were observed in bio-electrocatalytic system, especially in the external coupling system. Alpha diversity analysis further confirmed that bio-electrocatalytic system increased the diversity of the microbial community. The stainless-steel mesh based molybdenum carbide (SS-Mo₂C), which was prepared by a simple and low-cost impregnation method, significantly improved the electrocatalytic activity of anode, thus contributing to tetracycline removal in the bio-electrocatalytic system, especially in the external coupling system.

Removal of pharmaceuticals by vertical flow constructed wetland with different configurations: Effect of inlet load and biochar addition in the substrate

Pharmaceuticals (PCs) residues are considered an emerging threat to the environment due to their persistency, ecotoxicity and bioaccumulative nature. To study the PC (amoxicillin, AMX; caffeine, CF; ibuprofen, IBU) removal efficiency of vertical flow constructed wetland (VFCW), three setups of VFCWs were configured: SB (substrate matrix + biochar (BC)); SBP (substrate matrix + BC + plant); SP (substrate matrix + plant) and changes in effluent PC load was estimated at 24, 48, 72, 96, 120, 144 and 168 h intervals. SBP with an influent load of 1,000 μg L^-1 showed the maximum removals of 75.51% (AMX), 87.53% (CF), and 79.93% (IBU) significantly higher than that of SB and SP (p < 0.00). Results showed an inverse relationship between removal efficacy and influent PCs loading. The average removal (%) by VFCWS (of all studied setups) was in the order: 66.20 > 47.88 > 39.0 (IBU), 56.56 > 42.12 > 34.36 (AMX), and 74.13 > 64.0 > 52.07 (CF) with 1,000, 5,000 > 10,000 μg L^-1 influent load, respectively. The maximum removal of COD, NH₄⁺-N, and NO₃-N was recorded at 88.8%, 83.1%, and 64.9%, respectively in SBP, and their removal was hardly affected by influent PC concentration. In summary, planted VFCW spiked with BC could be a viable approach for the removal of PCs in wastewater. The impact of PC load on plant toxicity in VFCWs can be taken as a research problem for future work in this series.

Adaptation responses of microalgal-bacterial granular sludge to sulfamethoxazole

The presence of widely used sulfamethoxazole (SMX) in wastewater poses a threat to aquatic organisms and humans. Here, the responses of the emerging microalgal-bacterial granular sludge (MBGS) process in treating SMX-containing wastewater were investigated. The results indicated that 1, 5 and 10 mg/L SMX had little effect on the removals of organics and nutrients after an acclimation period of three to five days. SMX reduced intracellular glycogen content of MBGS, while the production of chlorophyll and extracellular polymeric substances tended to be promoted. Furthermore, the potential mechanisms on how MBGS adapted to SMX were deciphered to be the alterations of microbial community structure and function of MBGS. SMX might be degraded intracellularly into a carbon source for microbial metabolism and the SMX degraders were suspected to be Scenedesmaceae, Rhodocyclaceae and Burkholderiaceae. This study suggests that the MBGS process can handle SMX-containing wastewater, advancing knowledge on MBGS for antibiotics degradation.

Toward emerging contaminants removal using acclimated activated sludge in the gravity-driven membrane filtration system

The occurrence of emerging contaminants is attracting widespread attention due to its potential threat to aquatic organisms and public health. Gravity-driven membrane (GDM) filtration can effectively eliminate water contamination with pathogenic microorganisms in rural areas while being challenged by various micro-pollutants (MPs). This study investigated the removal and transformation of sulfamethoxazole (SMX) in GDM for the first time, and pre-adding acclimated activated sludge was proposed to improve the removal of MPs. More rapid and higher SMX degradation was observed with pre-adding domestication sludge, and the system had better tolerance to SMX shocks. Besides, in the presence of domesticated sludge, more SMX metabolic pathways and better mineralization rates were obtained, which was related to more SMX-resistant bacteria and easier biodegradable carbon sources in the system. Pre-adding sludge also increased the richness and diversity of bacterial community, which provided higher removal efficiencies of conventional pollutants. Thus, the removal rates of DOC (14.7%), NH₄⁺-N (5.6%) and fluorescent substances were obviously improved compared with the control group. In this study, the crisis of MPs was tackled and the removal of conventional pollutants was enhanced by pre-adding domesticated sludge in GDM, which ensured the water quality in rural areas.

Role of environmental stresses in elevating resistance mutations in bacteria: Phenomena and mechanisms

Mutations are an important origin of antibiotic resistance in bacteria. While there is increasing evidence showing promoted resistance mutations by environmental stresses, no retrospective research has yet been conducted on this phenomenon and its mechanisms. Herein, we summarized the phenomena of stress-elevated resistance mutations in bacteria, generalized the regulatory mechanisms and discussed the environmental and human health implications. It is shown that both chemical pollutants, such as antibiotics and other pharmaceuticals, biocides, metals, nanoparticles and disinfection byproducts, and non-chemical stressors, such as ultraviolet radiation, electrical stimulation and starvation, are capable of elevating resistance mutations in bacteria. Notably, resistance mutations are more likely to occur under sublethal or subinhibitory levels of these stresses, suggesting a considerable environmental concern. Further, mechanisms for stress-induced mutations are summarized in several points, namely oxidative stress, SOS response, DNA replication and repair systems, RpoS regulon and biofilm formation, all of which are readily provoked by common environmental stresses. Given bacteria in the environment are confronted with a variety of unfavorable conditions, we propose that the stress-elevated resistance mutations are a universal phenomenon in the environment and represent a nonnegligible risk factor for ecosystems and human health. The present review identifies a need for taking into account the pollutants' ability to elevate resistance mutations when assessing their environmental and human health risks and highlights the necessity of including resistance mutations as a target to prevent antibiotic resistance evolution.

Anaerobic electrochemical membrane bioreactor effectively mitigates antibiotic resistance genes proliferation under high antibiotic selection pressure

The spread of antibiotics and antibiotic resistance genes (ARGs) in environments has posed potential threats to public health. Unfortunately, conventional biological wastewater treatment technologies generally show insufficient removal of antibiotics and ARGs. Bioelectrochemical systems, which can effectively degrade refractory organic pollutants via enhancing microbial metabolisms through electrochemical redox reaction, may provide an alternative for the control of antibiotics and ARGs. Herein, an anaerobic electrochemical membrane bioreactor (AnEMBR) was conducted by combining bioelectrochemical system and anaerobic membrane bioreactor to treat antibiotic-containing wastewater. The AnEMBR at open circuit showed stable CH4 production and high removal of COD and chlortetracycline (CTC) in treating 2.5-15 mg/L CTC. However, increasing CTC to 45 mg/L completely inhibited the methanogenesis of AnEMBR at open circuit. After applying external voltage in AnEMBR, the performances of AnEMBR were significantly improved (e.g., increased CH4 production and CTC removal). Moreover, CTC exposure significantly increased the relative abundances of ARGs in sludge, supernatant, and effluent in AnEMBR at open circuit. Applying voltage greatly attenuated the total relative abundances of ARGs in the supernatant and effluent of AnEMBR compared to those at open circuit. This could be attributed to the enrichment of tetracycline degradation gene tetX, which greatly enhanced the removal of CTC by the AnEMBR and thus reduced the selective pressure of CTC on the microorganisms in supernatant and effluent for ARGs proliferation. These results would provide an effective wastewater treatment technology for treating high-level antibiotic-containing wastewater to mitigate the potential risk of ARGs and antibiotics spread in receiving water body.

Increase of antibiotic resistance genes via horizontal transfer in single- and two-chamber microbial electrolysis cells

Microbial electrolysis cells (MECs) have been applied for antibiotic degradation but simultaneously induced antibiotic resistance genes (ARGs), thus representing a risk to disseminate antibiotic resistance. However, few studies were on the potential and risk of ARGs transmission in the MECs. This work assessed conjugative transfer of ARGs under three tested conditions (voltages, cell concentration, and donor/recipient ratio) in both single- and two-chamber MECs. The results indicated that voltages (> 0.9 V) facilitated the horizontal frequency of ARGs in the single-chamber MECs and anode chamber of two-chamber MECs. The donor cell number (donor/recipient ratio was 2:1) increased the transfer frequency of ARGs. Furthermore, voltages ranged from 0.9 to 2.5 V increased reactive oxygen species (ROS) production and cell membrane permeability in MECs. These findings offer new insights into the roles of ARG transfer under different applied voltages in the MECs, which should not be ignored for horizontal transfer of antibiotic resistance.

An Overview of Antibiotic Resistance and Abiotic Stresses Affecting Antimicrobial Resistance in Agricultural Soils

Excessive use of antibiotics in the healthcare sector and livestock farming has amplified antimicrobial resistance (AMR) as a major environmental threat in recent years. Abiotic stresses, including soil salinity and water pollutants, can affect AMR in soils, which in turn reduces the yield and quality of agricultural products. The objective of this study was to investigate the effects of antibiotic resistance and abiotic stresses on antimicrobial resistance in agricultural soils. A systematic review of the peer-reviewed published literature showed that soil contaminants derived from organic and chemical fertilizers, heavy metals, hydrocarbons, and untreated sewage sludge can significantly develop AMR through increasing the abundance of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARBs) in agricultural soils. Among effective technologies developed to minimize AMR's negative effects, salinity and heat were found to be more influential in lowering ARGs and subsequently AMR. Several strategies to mitigate AMR in agricultural soils and future directions for research on AMR have been discussed, including integrated control of antibiotic usage and primary sources of ARGs. Knowledge of the factors affecting AMR has the potential to develop effective policies and technologies to minimize its adverse impacts.

Bibliometric analysis of microbial sulfonamide degradation: Development, hotspots and trend directions

Microbial sulfonamide degradation (MSD) is an efficient and safe treatment in both natural and engineered ecosystems. In order to systematically understand the research status and frontier trends of MSD, this study employed CiteSpace to conduct a bibliometric analysis of data from the Web of Science (WoS) and the China National Knowledge Infrastructure (CNKI) published from 2000 to 2021. During this time, China, Germany, Spain, the United States and Australia played leading roles by producing numerous high impact publications, while the Chinese Academy of Sciences was the leading research institution in this interdisciplinary research category. The Chemosphere was the top journal in terms of the number of citations. MSD research has gradually progressed from basic laboratory-based experiments to more complex environmental microbial communities and finally to deeper research on molecular mechanisms and engineering applications. Although multi-omics and synthetic community are the key techniques in the frontier research, they are also the current challenges in this field. A summary of published articles shows that Proteobacteria, Gammaproteobacteria, Burkholderiales and Alcaligenaceae are the most frequently observed MSD phylum, class, order and family, respectively, while Bacillus, Pseudomonas and Achromobacter are the top three MSD genera. To our knowledge, this study is the first to investigate the development and current challenges of MSD research, put forward future perspective, and form a relatively complete list of sulfonamide-degrading microorganisms for reference.

Role of bioelectrochemical systems for the remediation of emerging contaminants from wastewater: A review

Bioelectrochemical systems (BESs) are a unique group of wastewater remediating technology that possesses the added advantage of valuable recovery with concomitant wastewater treatment. Moreover, due to the application of robust microbial biocatalysts in BESs, effective removal of emerging contaminants (ECs) can be accomplished in these BESs. Thus, this review emphasizes the recent demonstrations pertaining to the removal of complex organic pollutants of emerging concern present in wastewater through BES. Owing to the recalcitrant nature of these pollutants, they are not effectively removed through conventional wastewater treatment systems and thereby are discharged into the environment without proper treatment. Application of BES in terms of ECs removal and degradation mechanism along with valuables that can be recovered are discussed. Moreover, the factors affecting the performance of BES, like biocatalyst, substrate, salinity, and applied potential are also summarized. In addition, the present review also elucidates the occurrence and toxic nature of ECs as well as future recommendations pertaining to the commercialization of this BES technology for the removal of ECs from wastewater. Therefore, the present review intends to aid the researchers in developing more efficient BESs for the removal of ECs from wastewater.

Performance and mechanism of sulfamethoxazole removal in different bioelectrochemical technology-integrated constructed wetlands

Sulfamethoxazole (SMX) has a high concentration and detection frequency in aquatic environments due to the poor removal efficiency of traditional biological treatment processes. Bioelectrochemical technology-integrated constructed wetlands (CWs) have great potential for SMX removal; however, the process of SMX removal in different bioelectrochemical technology-integrated CWs (microbial fuel cell (MFC) and direct current (EC)) remains unclear. To address this, we examined the mechanism of SMX removal in MFCCW and ECCW. The results revealed that the SMX removal efficiency can reach 96.0 ± 2.4% in the ECCW and 97.2 ± 2.2% in the MFCCW. The enhancement of MFC for SMX removal in CW was slightly better than that in direct current (p > 0.05). It was found that the adsorption process of SMX in the substrate promoted by EC was more enhanced than that by MFC. Furthermore, bioelectrochemical technology improved plant activity, including root and enzymatic (superoxide dismutase, peroxidase, and catalase) activities, and fluorescence parameters (photochemical quenching coefficient, non-photochemical quenching coefficient, and quantum efficiency of PS II). Significant differences were found between CW and ECCW (p < 0.05), while no significant differences were found between CW and MFCCW (p > 0.05). The microbial activity and abundance in CW were improved by bioelectrochemical technology, and the microbial community structure was optimised to be simpler and more stable. However, EC tended to promote microbial and plant activity in CW, whereas MFC tended to optimise the microbial community and improve the tightness and stability of the module. The enhanced difference might also account for the changes in the SMX degradation pathway. 4-aminobenzenesulfonic acid (TP174), 3-amino-5-methylisoxazole (TP99) and 5-methylisoxazole (TP84) were all common products in the three reactors, whereas TP99 underwent further ring-opening in MFCCW and TP174 underwent further hydrolysis in ECCW. This study provided an important reference for the targeted regulation of plants and microorganisms in constructed wetlands via different bioelectrochemistry to enhance characteristic pollutants degradation.

A review of the bioelectrochemical system as an emerging versatile technology for reduction of antibiotic resistance genes

Antibiotic contamination and the resulting resistance genes have attracted worldwide attention because of the extensive overuse and abuse of antibiotics, which seriously affects the environment as well as human health. Bioelectrochemical system (BES), a potential avenue to be explored, can alleviate antibiotic pollution and reduce antibiotic resistance genes (ARGs). This review mainly focuses on analyzing the possible reasons for the good performance of ARG reduction by BESs and potential ways to improve its performance on the basis of revealing the generation and transmission of ARGs in BES. This system reduces ARGs through two pathways: (1) the contribution of BES to the low selection pressure of ARGs caused by the efficient removal of antibiotics, and (2) inhibition of ARG transmission caused by low sludge yield. To promote the reduction of ARGs, incorporating additives, improving the removal rate of antibiotics by adjusting the environmental conditions, and controlling the microbial community in BES are proposed. Furthermore, this review also provides an overview of bioelectrochemical coupling systems including the BES coupled with the Fenton system, BES coupled with constructed wetland, and BES coupled with photocatalysis, which demonstrates that this method is applicable in different situations and conditions and provides inspiration to improve these systems to control ARGs. Finally, the challenges and outlooks are addressed, which is constructive for the development of technologies for antibiotic and ARG contamination remediation and blocking risk migration.

Efficacy of a novel electrochemical membrane-aerated biofilm reactor for removal of antibiotics from micro-polluted surface water and suppression of antibiotic resistance genes

An electrochemical membrane-aerated biofilm reactor (EMABR) was developed for removing sulfamethoxazole (SMX) and trimethoprim (TMP) from contaminated water. The exertion of electric field greatly enhanced the degradation of SMX and TMP in the EMABR (~60%) compared to membrane-aerated biofilm reactor (MABR, < 10%), due to the synergistic effects of the electro-oxidation (the generation of reactive oxygen species) and biological degradation. Microbial community analyses demonstrated that the EMABR enriched the genus of Xanthobacter, which was potentially capable of degrading aromatic intermediates. Moreover, the EMABR had a lower relative abundance of antibiotic resistance genes (ARGs) (0.23) compared to the MABR (0.56), suggesting the suppression of ARGs in the EMABR. Further, the SMX and TMP degradation pathways were proposed based on the detection of key intermediate products. This study demonstrated the potential of EMABR as an effective technology for removing antibiotics from micro-polluted surface water and suppressing the development of ARGs.

Antibiotic residues in wastewaters from sewage treatment plants and pharmaceutical industries: Occurrence, removal and environmental impacts

Sewage treatment plants (STPs) and pharmaceutical manufactories (PMFs) are recognized as important reservoirs for aquatic pollution with antibiotics. Although the occurrence of multiple classes of antibiotics has been mostly reported for STPs and PMFs, knowledge on the effects of wastewater treatment processes on the removal of antibiotics is not well documented. In this study, wastewaters were collected from different treatment points of two STPs and two PMFs in eastern China. Thirty-seven antibiotics within the four classes of fluoroquinolones (FQs), macrolides (MACs), sulfonamides (SAs) and tetracyclines (TCs) were analyzed. Among the investigated antibiotics, 19-33 out of 37 target compounds were detected at least once in the STPs wastewaters ranging from low ng/L to approximately 12.7 μ/L. In the wastewater samples collected from PMFs, up to 34 antibiotics were present with detection frequencies up to 100%, showing generally higher concentrations (up to 19.0 μ/L) than those at the STPs. FQs and SAs were the dominant antibiotic families, which accounted for more than 90% of the total antibiotic concentration in the wastewaters. Moreover, the removal of antibiotics by anaerobic-anoxic-oxic (A²O), membrane bioreactor (MBR) and conventional activated sludge (CAS) systems was evaluated. The MBR system exhibited the best performance, mainly due to the processes of biodegradation and sorption during biological treatments. Notably, several SAs (SMP, SMZ) and FQs (CIN, ENO) antibiotics were consistently detected at concentration levels of μ/L in the effluent samples. The culturable antibiotic-resistance tests and risk assessment indicated that the antibiotic-contaminated effluents would facilitate the development of resistant bacteria and pose high toxicity to non-target organisms in the aquatic environment. Overall, the findings suggested an urgent need for improving the wastewater treatment technologies for simultaneous removal of different classes of antibiotics.

Thiourea-assisted one-step fabrication of a novel nitrogen and sulfur co-doped biochar from nanocellulose as metal-free catalyst for efficient activation of peroxymonosulfate

The N, S co-doped biochar (N, S-BC) with multistage pore structure was successfully synthesized from nanocellulose and thiourea by one-step pyrolysis, which could effectively activate peroxymonosulfate (PMS) to degrade sulfamethoxazole (SMX) in water. Moreover, the removal efficiency of SMX by this oxidation system was 2.3-3.1 times than that of other systems activated by common metal oxides (such as Fe₃O₄、Fe₂O₃, and MnO₂). More importantly, the mechanism of the N, S-BC/PMS process was deduced by reactive oxygen species (ROS) quenching experiment and electron paramagnetic resonance (EPR) test, which exhibited that surface-bound free radicals and singlet oxygen (¹O₂) played an essential role in the SMX degradation. Surprisingly, the sulfate radical (SO₄^•-) and hydroxyl radical (^•OH) produced in this system existed in a bound state on the surface of the carbon catalyst to react with SMX, rather than dispersed in the aqueous solution. This particular form of free radicals could resist the influence of background substances and pH changes in water, and maintain excellent SMX degradation efficiency under different water matrices and pH. This study provides a new insight into the application of carbon catalyst in actual water pollution control.

Bioremoval and tolerance study of sulfamethoxazole using whole cell Trichoderma harzianum isolated from rotten tree bark

Antibiotic contamination raises concerns over antibiotic resistance genes (ARGs), which can severely impact the human health and environment. Sulfamethoxazole (SMX) is a widely used antibiotic that is incompletely metabolized in the body. In this study, the research objectives were (1) to isolate the native strain of Trichoderma sp. from the environment and analyze the tolerance toward SMX concentration by evaluating fungal growth, and (2) to investigate the potential of SMX removal by fungi. The potential fungi isolated from rotten tree bark showed 97% similarity to Trichoderma harzianum (Accession no. MH707098.1). The whole cell of fungi was examined in vitro; the strain Trichoderma harzianum BGP115 eliminated 71% of SMX after 7 days, while the white rot fungi Trametes versicolor, demonstrated 90% removal after 10 days. Furthermore, the tolerance of fungal growth toward SMX concentration at 10 mg L^-1 was analyzed, which indicated that Trichoderma harzianum BGP115 (the screened strain) exhibited more tolerance toward SMX than Trametes versicolor (the reference strain). The screened fungi isolated from rotted tree bark demonstrated the ability of SMX bioremoval and the potential to be tolerant to high concentrations of SMX.

Response of antibiotic and heavy metal resistance genes to tetracyclines and copper in substrate-free hydroponic microcosms with Myriophyllum aquaticum

Constructed wetlands for antibiotics and heavy metals removal have become important reservoirs of antibiotic resistance genes (ARGs) and heavy metal resistance genes (MRGs), especially in the substrates. Here, substrate-free hydroponic microcosms of Myriophyllum aquaticum were established; tetracyclines (TCs) and Cu(II) were added to evaluate the behaviours of ARGs and MRGs in the microcosms. Several ARGs, MRGs, and mobile genetic elements (MGE) were detected in the biofilms attached to the plants, ranging from 0.5 to 2.3 × 10⁸ copies/g dry weight. ARGs and MRGs exhibited higher relative abundances in the effluent suspended solids (SS); however, their absolute amounts were much lower than those in conventionally constructed wetlands. Microcosms with TCs and Cu(II) exhibited a higher level of resistant genes than those with compound added singularly owing to co-selection pressure. The existence of TCs and copper significantly changed the microbial communities in the microcosms. The exogenous input of TC/Cu(II) and microbial community structure were the factors driving the occurrence of ARGs, whereas MRGs were more correlated with the copper addition. Thus, reducing the exogenous inputs of antibiotics /heavy metals and SS of the effluent is suggested for the mitigation of resistant genes in phytoremediation technologies working in the absence of conventional substrates.

Microbial community dynamic shifts associated with sulfamethoxazole degradation in microbial fuel cells

Though sulfamethoxazole (SMX) degradation at the low or medium concentration (SMX< 30 mg/L) has been reported in the microbial fuel cell (MFC), further exploration is still urgently required to investigate how the high concentration of SMX affect the anode biofilm formation. In this study, the degradation mechanism of SMX and the response of microbial community to SMX at different initial concentrations (0, 0.5, 5 and 50 mg/L) were investigated in MFCs. The highest SMX removal efficiency of 98.4% was obtained in MFC (5 mg/L). SMX at optimal concentration (5 mg/L) could serve as substrate accelerating the extracellular electron transfer. However, high concentration of SMX (50 mg/L) conferred significant inhibition on the electron transfer with SMX removal decline to 84.4%. The 16S rRNA high-throughput sequencing revealed the significant shift of the anode biofilms communities with different initial SMX concentrations were observed in MFCs. Thauera and Geobacter were the predominant genus, with relative abundance of 31.9% in MFC (50 mg/L SMX) and 52.7% in MFC (5 mg/L SMX). Methylophilus exhibited a huge increase with the highest percentage of 16.4% in MFC (50 mg/L). Hence, the functional bacteria of Thauera, Geobacter and Methylophilus endowed significant tolerance to the selection pressure from high concentration of SMX in MFCs. Meanwhile, some bacteria including Ornatilinea, Dechloromonas and Longilinea exhibited a decrease or even disappeared in MFCs. Therefore, initial concentrations of SMX played a fundamental role in modifying the relative abundance of predominant populations. This finding would promote theories support for understanding the evolution of anode biofilm formation related to the different initial concentrations of SMX in MFCs.

Efficient degradation of polyacrylate containing wastewater by combined anaerobic-aerobic fluidized bed bioreactors

Polyacrylate containing wastewater (PCW) is the typical sewage discharged by the textile industry. It has extremely poor biodegradability, and chemical methods were used conventionally as the only way for treating PCW. This study is demonstrating a novel biological method. In batch experiment monod kinetics was applied to the experimental data, which indicated that anaerobic treatment used for PCW is feasible. The pilot-scale experiment combined a Spiral Symmetry Stream Anaerobic Bioreactor (SSSAB) and an air-lift external circulation vortex enhancement nitrogen removal fluidized bed bioreactor (AFB). The COD and NH₄⁺-N removal reached up to 95.2% and 96.6%, respectively, which were higher than the value obtained by other chemical methods. High-throughput sequencing analysis indicated that the relative abundance of Proteobacteria, Firmicutes and Bacteroidetes increased, which contribute to the degradation of PCW. Therefore, PCW can be degraded efficiently by using a SSSAB-AFB technique and thus provides an alternative to the chemical methods.

Bioaugmentation of Moving Bed Biofilm Reactor (MBBR) with Achromobacter JL9 for enhanced sulfamethoxazole (SMX) degradation in aquaculture wastewater

This study investigated whether bioaugmentation improves sulfamethoxazole (SMX) degradation and nitrogen removal in the Moving Bed Biofilm Reactor (MBBR) system. The effects of the C/N ratio on SMX degradation and nitrogen removal were also evaluated. Using MBBR system operation experiments, the bioaugmented reactor was found to perform more effectively than the non-bioaugmentation reactor, with the highest SMX, nitrate-N, and ammonia-N removal efficiencies of 80.49, 94.70, and 96.09%, respectively. The changes in the sulfonamide resistance genes and bacterial communities were detected at various operating conditions. The results indicate that the diversity of the bacterial communities and the abundance of resistance genes were markedly influenced by bioaugmentation and the C/N ratio, with Achromobacter among the dominant genera in the MBBR system. The bio-toxicity of samples, calculated as the inhibition percentage (IP) toward Escherichia coli, was found to decrease to non-toxic ranges after treatment.

Variation and distribution of antibiotic resistance genes and their potential hosts in microbial electrolysis cells treating sewage sludge

Microbial electrolysis cells (MECs) system is an emerging pollution control technology. However, information on the variation of antibiotic resistance genes (ARGs) in MECs treating sewage sludge is still very limited. In this study, the fate of ARGs and their correlation with microbes in MECs under different applied voltages (0-1.5 V) were studied. Most target ARGs were effectively removed, but tetB, tetM and tetQ were enriched up to 2.05 log units in suspended sludge. Most ARGs were mainly distributed on electrodes, except tetQ and tetM enriched in suspended sludge. The selective pressure of residual antibiotics in the sewage sludge was negligible. Horizontal gene transfer was validated for the spread of sul1, sul2, tetA and tetC in MECs. Network analysis revealed that the potential hosts of ARGs mainly belonged to Bacteroidetes, Firmicutes and Proteobacteria. Some genera related to electron transfer were newly found to be the potential ARGs hosts in MECs.

Potential of Myriophyllum aquaticum for phytoremediation of water contaminated with tetracycline antibiotics and copper

Water pollution caused by antibiotics and heavy metals has attracted considerable concern, and efficient approaches are urgently needed for their removal. The objective of this study was to investigate the potential of Myriophyllum aquaticum for long-term phytoremediation of wastewater containing tetracycline (TC) antibiotics and copper. Seven hydroponic microcosms were constructed, spiked with tetracycline, oxytetracycline (OTC) and chlortetracycline (CTC) (300-30,000 μg/L), alone or simultaneously with Cu (II), and operated for 12 weeks. The TC removal efficiencies using the hydroponic microcosms here were commensurate or higher than those in previous studies. However, the Cu/TC ratio greatly affected the removal, accumulation of TCs by M. aquaticum, and plant growth. Low levels of Cu (II) (<1000 μg/L) promoted TC removal, but excessive Cu (II) (>10,000 μg/L) impeded it. Mass balance analysis showed that most TCs (45%-64% on average) accumulated in the roots of M. aquaticum. Plant biomass was correlated with the removal of COD, TN, TP, and NH₄⁺-N (p ≤ 0.05) but not with removal of the TCs. Proteobacteria, Bacteroidetes, and Fusobacteria were dominant in the microbial communities, but they showed little correlation with the TC removal. M. aquaticum can be employed as an effective means of TC removal from water. The co-existence of heavy metals should be considered when evaluating the removal potential of TCs in phytoremediation.

Simultaneous removal and high tolerance of norfloxacin with electricity generation in microbial fuel cell and its antibiotic resistance genes quantification

Norfloxacin (NFLX) is a synthetic antibiotic widely used in the treatment of infectious diseases. In this work, the performance of microbial fuel cells (MFCs) toward NFLX degradation, electricity production and the antibiotics resistances genes (ARGs) generation was investigated. NFLX degradation efficiency and COD removal reached 65.5% and 94.5% respectively. The increase in NFLX concentration (128 mg/L) had no significant influence on NFLX degradation efficiency, COD removal and MFCs voltage output while the electricity was successfully generated. The quantitative polymerase chain reaction (qPCR) indicated low absolute abundances of ARGs (mdtk, mdtm, and pmra) compared with the traditional wastewater treatment plants (WWTPs). Anodic bacteria can survive in the presence of high NFLX concentration and sustain its degradation and electricity production. In terms of NFLX degradation, COD removal, diminished ARGs generation and simultaneous energy production, MFC seems to be a promising technology for antibiotics wastewater treatment with a potential to overcome the ARGs challenge.

Effect of the coexposure of sulfadiazine, ciprofloxacin and zinc on the fate of antibiotic resistance genes, bacterial communities and functions in three-dimensional biofilm-electrode reactors

Three-dimensional biofilm electrode reactors (3D-BERs) with high treatment efficiency were constructed to treat wastewater containing sulfadiazine (SDZ) and ciprofloxacin (CIP) coexposure with Zinc (Zn). The results showed that coexposure to target antibiotics and Zn increased the absolute and relative abundances of target antibiotic resistance genes (ARGs). Additionally, the target ARG abundances were higher on cathode of 3D-BER compared with ordinary anaerobic reactor while the abundances of total ARGs were decreased in the effluent. Meanwhile, redundancy analysis results revealed that the composition of bacteria carrying ARGs was greatly influenced in the cathode by the accumulation of Zn and antibiotic, which dominated the changes of ARG abundances. Additionally, ARGs with their host bacteria revealed by network analysis were partially deposited on electrode substrates when being removed from wastewater. Thus, 3D-BER exhibits capability of simultaneously eliminating antibiotic and Zn, and greatly reduces the risks of ARGs spread.