Size-dependent promotion of micro(nano)plastics on the horizontal gene transfer of antibiotic resistance genes in constructed wetlands. - Related Documents




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797901.0000Size-dependent promotion of micro(nano)plastics on the horizontal gene transfer of antibiotic resistance genes in constructed wetlands. Constructed wetlands (CWs) have been identified as significant sources of micro(nano)plastics (MPs/NPs) and antibiotic resistance genes (ARGs) in aquatic environments. However, little is known about the impact of MPs/NPs exposure on horizontal gene transfer (HGT) of ARGs and shaping the corresponding ARG hosts' community. Herein, the contribution of polystyrene (PS) particles (control, 4 mm, 100 μm, and 100 nm) to ARG transfer was investigated by adding an engineered fluorescent Escherichia coli harboring RP4 plasmid-encoded ARGs into CWs. It was found MPs/NPs significantly promoted ARG transfer in a size-dependent manner in each CW medium (p < 0.05). The 100 μm-sized PS exhibited the most significant promotion of ARG transfer (p < 0.05), whereas 100 nm-sized PS induced limited promotion due to its inhibitory activity on microbes. The altered RP4-carrying bacterial communities suggested that MPs/NPs, especially 100 µm-PS, could recruit pathogenic and nitrifying bacteria to acquire ARGs. The increased sharing of RP4-carrying core bacteria in CW medium further suggested that ARGs can spread into CW microbiome using MPs/NPs as carriers. Overall, our results highlight the high risks of ARG dissemination induced by MPs/NPs exposure and emphasize the need for better control of plastic disposal to prevent the potential health threats.202337657315
797810.9999Metagenomic insight into the enrichment of antibiotic resistance genes in activated sludge upon exposure to nanoplastics. Activated sludge is an important reservoir for the co-occurring emerging contaminants including nanoplastics (NPs) and antibiotic resistance genes (ARGs). However, the impacts and potential mechanisms of NPs on the fate of ARGs in activated sludge are not fully understood. Herein, we used metagenomic approach to investigate the responses of ARGs, host bacteria, mobile genetic elements (MGEs), and functional genes to polystyrene (PS) NPs at environmentally relevant (0.5 mg/L) and high stress concentrations (50 mg/L) in activated sludge. The results showed that 0.5 and 50 mg/L PS NPs increased the relative abundance of ARGs in the activated sludge by 58.68% and 46.52%, respectively (p < 0.05). Host tracking analysis elucidated that the hosts of ARGs were significantly enriched by PS NPs (p < 0.05), with Proteobacteria being the predominant host bacteria. Additionally, the occurrence of new ARGs hosts and the enrichment of MGEs and functional genes (i.e., genes related to SOS response, cell membrane permeability, and secretion system, etc.) indicated that PS NPs promoted horizontal gene transfer (HGT) of ARGs. Finally, path modeling analysis revealed that the proliferation of ARGs caused by PS NPs was primarily attributed to the enhancement of HGT and the enrichment of host bacteria. Our findings contribute to a comprehensive understanding of the spread risk of ARGs in activated sludge under NPs pollution.202439510298
703220.9999Free Radicals on Aging Microplastics Regulated the Prevalence of Antibiotic Resistance Genes in the Aquatic Environment: New Insight into the Effect of Microplastics on the Spreading of Biofilm Resistomes. The spread of antibiotic resistance genes (ARGs) by microplastics has received a great concern in coexisting "hotspots". Despite most microplastics suffering from natural aging, little is known about the effect of aging microplastics (A-MPs) on ARGs dissemination. Here, we demonstrated significant suppression of A-MPs on ARGs dissemination in natural rivers. Although ARGs and mobile genetic elements (MGEs) were effectively enriched on A-MPs, the relative abundance of ARGs and MGEs on A-MPs as well as in receiving water decreased by approximately 21.4% to 42.3% during a period of 30 days of dissemination. Further investigation revealed that (•)OH was consistently generated on A-MPs with a maximum value of 0.2 μmol/g. Importantly, scavenging of (•)OH significantly increased the relative abundance of ARGs and MGEs both on A-MPs and in receiving water 1.4-29.1 times, indicating the vital role of (•)OH in suppressing ARGs dissemination. Microbial analysis revealed that (•)OH inhibited the potential antibiotic-resistant bacteria in surface biofilms, such as Pseudomonas and Acinetobacter (with a decrease of 68.8% and 89.3%). These results demonstrated that (•)OH was extensively produced on A-MPs, which greatly reduced both the vertical and horizontal gene transfer of ARGs. This study provided new insights into the dissemination of ARGs through microplastics in natural systems.202540359213
858430.9998Microplastics enhance the prevalence of antibiotic resistance genes in mariculture sediments by enriching host bacteria and promoting horizontal gene transfer. Microplastics (MPs) and antibiotic resistance genes (ARGs) pose significant challenges to the One Health framework due to their intricate and multifaceted ecological and environmental impacts. However, the understanding of how MP properties influence ARG prevalence in mariculture sediments remains limited. Herein, the polystyrene (PS) and polyvinyl chloride (PVC) MPs with different sizes (20-120 μm and 0.5-2.0 mm) were selected to evaluate their impacts and underlying mechanisms driving ARGs dissemination. The results showed that PS and PVC MPs increased the relative abundance of ARGs by 1.41-2.50-fold and 2.01-2.84-fold, respectively, compared with control, particularly high-risk genes. The polymer type effect was identified as more influential than the size effect in driving the sediment resistome evolution. PVC shifted the microbial community assembly from stochastic to deterministic processes, thus enriching ARG host pathogens. Furthermore, the highly hydrophobic PS not only recruited the host bacteria colonization but also facilitated ARG exchange within the plastisphere. The exogenous additives released by PVC (e.g., heavy metals, bisphenol A, and tridecyl ester) and the particles synergistically promoted ARG conjugative transfer by inducing oxidative stress and enhancing cell membrane permeability. These findings revealed how MPs characteristics facilitated the spread of ARGs in marine benthic ecosystems, underscoring the importance of mitigating MPs pollution to maintain mariculture ecosystem health, prevent zoonotic diseases, and balance global mariculture with ecological health.202540052062
798040.9998Effect of dissolved biochar on the transfer of antibiotic resistance genes between bacteria. The spread of antibiotic resistance genes (ARGs) is a global environmental issue. Dissolved biochar is more likely to contact bacteria in water, producing ecological risks. This study explored the effects of dissolved biochar on ARGs transfer in bacteria. Conjugative transfer efficiency was significantly different following treatment with different types of dissolved biochar. Typically, humic acid-like substance in dissolved biochar can significantly improve the transfer efficiency of ARGs between bacteria. When the concentration of dissolved biochar was ≤10 mg biochar/mL, humic acid-like substance substantially promoted ARGs transfer. An increase in dissolved biochar concentration weakened the ARGs transfer from humic acid-like substance. The inhibitory effects of small-molecule matters dominated, decreasing conjugative transfer frequency. At a concentration of 100 mg biochar/mL, the conjugative transfer efficiency of all treatments was lower than that of control. Compared with corn straw dissolved biochar, there were more transconjugants in pine sawdust dissolved biochar. Following treatment with 10 mg biochar/mL pine sawdust dissolved biochar, the number of transconjugants was at its maximum; approximately 7.3 folds higher than the control. We also explored mechanisms by which dissolved biochar impacts conjugative transfer. Due to the complex composition of dissolved biochar, its effects on the expression of conjugative transfer-related genes were also dynamic. This study investigates the ecological risk of biochar and guides its scientific application.202134274650
793150.9998The stress response of tetracycline resistance genes and bacterial communities under the existence of microplastics in typical leachate biological treatment system. Landfill leachate is an important source of microplastics (MPs) and antibiotic-resistance genes (ARGs). Here, in the presence of polystyrene MPs (PS-MPs) and polyethylene MPs (PE-MPs), the nitrogen and phosphorus removal effect and sludge structure performance were affected in an anaerobic-anoxic-aerobic system, a typical biological leachate treatment process. The abundance of tetracycline-resistance genes (tet genes) in biofilms on the two types of MP was significantly higher than that in the leachate and sludge, and the load on PE-MPs was higher than that on PS-MPs because of the porous structure of PE-MPs. Aging of the MPs increased their surface roughness and abundance of oxygen-containing functional groups and shaped the profile of ARGs in the MP biofilms. The biofilm biomass and growth rate on the two types of MP increased with the incubation time in the first 30 days, and was affected by environmental factors. Structural equation models and co-occurrence network analysis demonstrated that the MPs indirectly affected the spectrum of ARGs by affecting biofilm formation, and, to a lesser extent, had a direct impact on the selective enrichment of ARGs. We discuss the mechanisms of the relationships between MPs and ARGs in the leachate treatment system, which will have guiding significance for future research. Our data on the colonization of microorganisms and tet genes in MPs biofilms provide new evidence concerning the accumulation and transmission of these ARGs, and are important for understanding the mechanisms of MPs in spreading pollution.202439018858
808360.9998Alteration of the migration trajectory of antibiotic resistance genes by microplastics in a leachate activated sludge system. The environmental behavior of emerging contaminants of microplastics (MPs), antibiotics and antibiotic resistance genes (ARGs) in the leachate activated sludge system has been monitored and analyzed comprehensively. The results suggested that MPs could effectively alter the migration trajectory of tetracycline resistance genes (tet genes) in the leachate activated sludge system under intermittent and continuous influent conditions. After adding MPs, the total average abundance of tet genes in leachate increased from 0.74 ± 0.07 to 0.78 ± 0.07 (log(10)tet genes/log(10) 16S rRNA) and that in sludge increased from 0.65 ± 0.08 to 0.70 ± 0.06 (log(10)tet genes/log(10) 16S rRNA). Except for tetA, the abundance of tetB, tetO, tetM and tetQ on MPs increased with increasing TC concentration under both aerobic and anaerobic conditions. MPs not only significantly affect the abundance level and migration trajectory of ARGs in the leachate activated sludge system, but also remarkably improve the level of heavy metals in the ambient environment, indirectly promoting the selective effect of antibiotic-resistant bacteria (ARB) and promoting the development of antibiotic resistance (AR). In addition, MPs changed their physicochemical properties and released hazardous substances with aging to force tet genes to migrate from the leachate activated sludge system to the MPs, making AR more difficult to eliminate and persisted in wastewater treatment plants. Meanwhile, microorganisms played a driving role, making MPs serve as a niche for ARGs and ARB colonization. The co-occurrence network analysis indicated the specific distribution pattern of tet genes and microorganisms in different media, and the potential host was speculated. This study improves the understanding of the environmental behavior of emerging contaminants in leachate activated sludge system and lays a theoretical for protecting the ecological environment.202337321316
750270.9998Differential dose-response patterns of intracellular and extracellular antibiotic resistance genes under sub-lethal antibiotic exposure. Although antibiotics are one of the most significant factors contributing to the propagation of antibiotic resistance genes (ARGs), studies on the dose-response relationship at sub-lethal concentrations of antibiotics remain scarce, despite their importance for assessing the risks of antibiotics in the environment. In this study, we constructed a series of microcosms to investigate the propagation of intracellular (iARGs) and extracellular (eARGs) ARGs in both water and biofilms when exposed to antibiotics at various concentrations (1-100 μg/L) and frequencies. Results showed that eARGs were more abundant than iARGs in water, while iARGs were the dominant ARGs form in biofilms. eARGs showed differentiated dose-response relationships from iARGs. The abundance of iARGs increased with the concentration of antibiotics as enhanced selective pressure overcame the metabolic burden of antibiotic-resistant bacteria carrying ARGs. However, the abundance of eARGs decreased with increasing antibiotic concentrations because less ARGs were secreted from bacterial hosts at higher concentrations (100 μg/L). Furthermore, combined exposure to two antibiotics (tetracycline & imipenem) showed a synergistic effect on the propagation of iARGs, but an antagonistic effect on the propagation of eARGs compared to exposure to a single antibiotic. When exposed to antibiotic at a fixed total dose, one-time dosing (1 time/10 d) favored the propagation of iARGs, while fractional dosing (5 times /10 d) favored the propagation of eARGs. This study sheds light on the propagation of antibiotic resistance in the environment and can help in assessing the risks associated with the use of antibiotics.202337257347
756380.9998Polystyrene microplastics alleviate the effects of sulfamethazine on soil microbial communities at different CO(2) concentrations. Microplastics were reported to adsorb antibiotics and may modify their effects on soil systems. But there has been little research investigating how microplastics may affect the toxicities of antibiotics to microbes under future climate conditions. Here, we used a free-air CO(2) enrichment system to investigate the responses of soil microbes to sulfamethazine (SMZ, 1 mg kg(-1)) in the presence of polystyrene microplastics (PS, 5 mg kg(-1)) at different CO(2) concentrations (ambient at 380 ppm and elevated at 580 ppm). SMZ alone decreased bacterial diversity, negatively affected the bacterial structure and inter-relationships, and enriched the sulfonamide-resistance genes (sul1 and sul2) and class 1 integron (intl1). PS, at both CO(2) conditions, showed little effect on soil bacteria but markedly alleviated SMZ's adverse effects on bacterial diversity, composition and structure, and inhibited sul1 transmission by decreasing the intl1 abundance. Elevated CO(2) had limited modification in SMZ's disadvantages to microbial communities but markedly decreased the sul1 and sul2 abundance. Results indicated that increasing CO(2) concentration or the presence of PS affected the responses of soil microbes to SMZ, providing new insights into the risk prediction of antibiotics under future climate conditions.202133592488
857890.9998Impact of earthworms on suppressing dissemination of antibiotic resistance genes during vermicomposting treatment of excess sludge. Earthworms play a crucial role in suppressing the dissemination of antibiotic resistance genes (ARGs) during vermicomposting. However, there is still a lack of how earthworms influence the spread of ARGs. To address this gap, a microcosm experiment was conducted, incorporating earthworms and utilizing metagenomics and quantitative PCR to assess the impact of earthworms on microbial interactions and the removal of plasmid-induced ARGs. The findings revealed that vermicomposting led to a reduction in the relative abundance of ARGs by altering microbial communities and interactions. Significantly, vermicomposting demonstrated an impressive capability, reducing 92% of ARGs donor bacteria and impeding the transmission of 94% of the RP4 plasmid. Furthermore, through structural equation model analysis, it was determined that mobile genetic elements and environmental variables were the primary influencers of ARG reduction. Overall, this study offers a fresh perspective on the effects of vermicomposting and its potential to mitigate the spread of ARGs.202438885722
8583100.9998Microplastics Enhance the Prevalence of Antibiotic Resistance Genes in Anaerobic Sludge Digestion by Enriching Antibiotic-Resistant Bacteria in Surface Biofilm and Facilitating the Vertical and Horizontal Gene Transfer. Antibiotic resistance genes (ARGs) and microplastics (MPs) are recognized as emerging contaminants and threats to global human health. Despite both of them being significantly detected in their "hotspots", i.e., waste activated sludge (WAS), rare studies on how MPs affect ARGs and antibiotic-resistant bacteria (ARB) in anaerobic sludge digestion are available. Herein, the fate of ARGs and ARB after exposure to MPs of three dosages (10, 30, and 80 particles/g-TS), three polymer types (LDPE, PET, and PS), and three branching extents (LDPE, LLDPE, and HDPE) in anaerobic sludge digestion was investigated. Metagenomic results indicated that all variants of MPs resulted in an increase of the relative abundance of ARGs in the digester compared to the control. The abundance of ARGs demonstrated a dosage-dependent relationship within the range from 10 to 80 particles/g-TS, resulting in an increase from 4.5 to 27.9% compared to the control. Branching structure and polymer type influence ARG level in the sludge digester as well. Mechanism studies revealed that LDPE selectively enriched potential ARB and ARGs in the surface biofilm, possibly creating a favorable environment for ARB proliferation and ARG exchange. Furthermore, vertical transfer of ARGs was facilitated by LDPE through increasing bacterial cell proliferation accompanied by the enhancement of relevant functional genes. The elevated abundance of mobile genetic elements (MGEs) and ARGs-carrying plasmids also demonstrated that MGE-mediated horizontal transfer was promoted by LDPE at 80 particles/g-TS. This effect was compounded by increased oxidative stress, cell membrane permeability, and cell cohesion, collectively facilitating horizontal ARG transfer. Consequently, both vertical and horizontal transfer of ARGs could be concurrently promoted by LDPE an in anaerobic sludge digester.202337733635
8588110.9998Does lipid stress affect performance, fate of antibiotic resistance genes and microbial dynamics during anaerobic digestion of food waste? The dissemination of antibiotic resistance genes (ARGs) in food waste (FW) disposal can pose severe threats to public health. Lipid is a primary composition in FW, while whether lipid stress can affect ARGs dynamics during anaerobic digestion (AD) process of FW is uncertain. This study focused on the impacts of lipid stress on methane production, fate of ARGs and its microbial mechanisms during AD of FW. Results showed that high lipid content increased methane yield but prolonged hydrolysis and lag time of methane production compared to AD of FW without oil. Moreover, variations of ARGs were more susceptible to lipid stress. Lipid stress could facilitate the reduction of total ARGs abundances compared to the group without oil, particularly restraining the proliferation of sul1, aadA1 and mefA in AD systems (P < 0.05). Mantel test suggested that integrons (intl1 and intl2) were significantly correlated with all detected ARGs (r: 0.33, P < 0.05), indicating that horizontal gene transfer mediated by integrons could be the driving force on ARGs dissemination. Network analysis suggested that Firmicutes, Bacteroidetes, Synergistetes and Proteobacteria were the main potential hosts of ARGs. In addition, under the lipid stress, the reduction of host bacteria was responsible for the elimination of several specific ARGs, thereby affecting ARGs profiles. These findings firstly deciphered ARGs dynamics and their driving factors responding to lipid stress during anaerobic biological treatment of FW.202133250254
7531120.9998Microplastics exacerbate co-occurrence and horizontal transfer of antibiotic resistance genes. Microplastic pollution is a rising environmental issue worldwide. Microplastics can provide a niche for the microbiome, especially for antibiotic-resistant bacteria, which could increase the transmission of antibiotic resistance genes (ARGs). However, the interactions between microplastics and ARGs are still indistinct in environmental settings. Microplastics were found to be significantly correlated with ARGs (p < 0.001), based on the analysis of samples taken from a chicken farm and its surrounding farmlands. Analysis of chicken feces revealed the highest abundance of microplastics (14.9 items/g) and ARGs (6.24 ×10(8) copies/g), suggesting that chicken farms could be the hotspot for the co-spread of microplastics and ARGs. Conjugative transfer experiments were performed to investigate the effects of microplastic exposure for different concentrations and sizes on the horizontal gene transfer (HGT) of ARGs between bacteria. Results showed that the microplastics significantly enhanced the bacterial conjugative transfer frequency by 1.4-1.7 folds indicating that microplastics could aggravate ARG dissemination in the environment. Potential mechanisms related to the up-regulation of rpoS, ompA, ompC, ompF, trbBp, traF, trfAp, traJ, and down-regulation of korA, korB, and trbA were induced by microplastics. These findings highlighted the co-occurrence of microplastics and ARGs in the agricultural environment and the exacerbation of ARGs' prevalence via rising the HGT derived from microplastics.202336878032
7033130.9998Environmental drivers and interaction mechanisms of heavy metal and antibiotic resistome exposed to amoxicillin during aerobic composting. The environmental accumulation and spread of antibiotic resistance pose a major threat to global health. Aerobic composting has become an important hotspot of combined pollution [e.g., antibiotic resistance genes (ARGs) and heavy metals (HMs)] in the process of centralized treatment and resource utilization of manure. However, the interaction mechanisms and environmental drivers of HMs resistome (MRGs), antibiotic resistance (genotype and phenotype), and microbiome during aerobic composting under the widely used amoxicillin (AMX) selection pressure are still poorly understood. Here, we investigated the dynamics of HMs bioavailability and their MRGs, AMX-resistant bacteria (ARB) and antibiotic resistome (ARGs and intI1), and bacterial community to decipher the impact mechanism of AMX by conducting aerobic composting experiments. We detected higher exchangeable HMs and MRGs in the AMX group than the control group, especially for the czrC gene, indicating that AMX exposure may inhibit HMs passivation and promote some MRGs. The presence of AMX significantly altered bacterial community composition and AMX-resistant and -sensitive bacterial structures, elevating antibiotic resistome and its potential transmission risks, in which the proportions of ARB and intI1 were greatly increased to 148- and 11.6-fold compared to the control group. Proteobacteria and Actinobacteria were significant biomarkers of AMX exposure and may be critical in promoting bacterial resistance development. S0134_terrestrial_group was significantly negatively correlated with bla(TEM) and czrC genes, which might play a role in the elimination of some ARGs and MRGs. Except for the basic physicochemical (MC, C/N, and pH) and nutritional indicators (NO(3) (-)-N, NH(4) (+)-N), Bio-Cu may be an important environmental driver regulating bacterial resistance during composting. These findings suggested the importance of the interaction mechanism of combined pollution and its synergistic treatment during aerobic composting need to be emphasized.202236687604
8589140.9998Impacts of microplastic type on the fate of antibiotic resistance genes and horizontal gene transfer mechanism during anaerobic digestion. Microplastics (MPs) and antibiotic resistance genes (ARGs) are important pollutants in waste activated sludge (WAS), but their interactions during anaerobic digestion (AD) still need to be further explored. This study investigated variations in ARGs, mobile genetic elements (MGEs), and host bacteria during AD under the pressure of polyamide (PA), polyethylene (PE), and polypropylene (PP). The results showed that the MPs increased methane production by 11.7-35.5%, and decreased ARG abundance by 5.6-24.6%. Correlation analysis showed that the decrease of MGEs (plasmid, prophage, etc.) promoted the decrease of the abundance of multidrug, aminoglycoside and tetracycline resistance genes. Metagenomic annotation revealed that the reduction of key host bacteria (Arenimonas, Lautropia, etc.) reduced the abundance of major ARGs (rsmA, rpoB2, etc.). Moreover, PP MPs contributed to a reduction in the abundance of functional genes related to the production of reactive oxygen species, ATP synthesis, and cell membrane permeability, which was conducive to reducing the potential for horizontal gene transfer of ARGs. These findings provide insights into the treatment of organic waste containing MPs.202438772228
7042150.9998Response of antibiotic resistance genes abundance by graphene oxide during the anaerobic digestion of swine manure with copper pollution. The pollution of various environments with antibiotic resistance genes (ARGs) is an urgent problem that needs to be addressed, especially in heavy metal-polluted environments. This study investigated the responses of ARGs and mobile genetic elements (MGEs) to the addition of graphene oxide (GO) to swine manure containing a high concentration copper during anaerobic digestion. The total copy numbers of ARGs and MGEs were significantly enhanced by the pressure due to Cu. GO significantly decreased the ARG and MGE copy numbers, where the low GO concentration performed better than the high GO concentration. Network analysis showed that most of the ARGs and MGEs co-occurred and they shared the same major potential host bacteria. The contributions of different factors to ARG abundances were assessed by redundancy analysis and MGEs had the most important effect on the fate of ARGs. Thus, GO may reduce the abundance of ARGs mainly by removing MGEs.201930445329
7566160.9998Antibiotic sulfadiazine degradation by persulfate oxidation: Intermediates dependence of ecotoxicity and the induction of antibiotic resistance genes. To preserve the water resources, this study has analyzed the ecotoxicity and antibiotic resistance genes (ARGs) induction capacity of sulfadiazine degradation intermediates resulting from persulfate activation oxidation enhanced by ultraviolet, ultrasound and microwave. The five degradation pathways caused by the contribution discrepancy of electron transfer and singlet oxygen ((1)O(2)) and variations in the ecotoxicity of different degradation products were analyzed. Microcosm experiment exhibited that the microbial community in actual water changed significantly with SDZ and degradation intermediates, in which the dominant genera were Aeromonas, Cupriavidus, Elizabethkingia and Achromobacter. Except for the selective pressure on bacteria, the degradation intermediates also exert a certain degree or even stronger induction on sulfonamide ARGs (sul4, sul1 and sul2) than SDZ. Furthermore, the potential hosts for sulfonamide ARGs were revealed by network analysis. These results provide a better understanding of antibiotics degradation mechanism and ARGs occurrence, which is useful for controlling the spread of ARGs.202336372382
8591170.9998Nanoscale zero-valent iron alleviate antibiotic resistance risk during managed aquifer recharge (MAR) by regulating denitrifying bacterial network. The frequent occurrence of antibiotics in reclaimed water is concerning, in the case of managed aquifer recharge (MAR), it inevitably hinders further water purification and accelerates the evolutionary resistance in indigenous bacteria. In this study, we constructed two column reactors and nanoscale zero-valent iron (nZVI) amendment was applied for its effects on water quality variation, microbial community succession, and antibiotic resistance genes (ARGs) dissemination, deciphered the underlying mechanism of resistance risk reduction. Results showed that nZVI was oxidized to iron oxides in the sediment column, and total effluent iron concentration was within permissible limits. nZVI enhanced NO(3)(-)-N removal by 15.5% through enriching denitrifying bacteria and genes, whereas made no effects on oxacillin (OXA) removal. In addition, nZVI exhibited a pivotal impact on ARGs and plasmids decreasing. Network analysis elucidated that the diversity and richness of ARG host declined with nZVI amendment. Denitrifying bacteria play a key role in suppressing horizontal gene transfer (HGT). The underlying mechanisms of inhibited HGT included the downregulated SOS response, the inhibited Type-Ⅳ secretion system and the weakened driving force. This study afforded vital insights into ARG spread control, providing a reference for future applications of nZVI in MAR.202438134694
7981180.9998Dissolved biochar eliminates the effect of Cu(II) on the transfer of antibiotic resistance genes between bacteria. The proliferation of antibiotic resistance genes (ARGs) has posed significant risks to human and environmental health. Research has confirmed that Cu(II) could accelerate the conjugative transfer of ARGs between bacteria. This study found that adding dissolved biochar effectively weakened or eliminated the Cu(II)-facilitated efficient transfer of ARGs. The efficiency of conjugative transfer was promoted after treatment with Cu(II) (0.05 mg/L) or dissolved biochar at a pyrolysis temperature of 300 °C. When exposed to the combination of Cu(II) and dissolved biochar, the transfer frequency was significantly reduced; this occurred regardless of the Cu(II) concentration or pyrolysis temperature of dissolved biochar. In particular, when the Cu(II) concentration exceeded 0.5 mg/L, the transfer efficiency was entirely inhibited. Gene expression analysis indicated that different treatments affect transfer efficiency by regulating the expression of three global regulatory genes: korA, korB, and trbA. Among them, humic acid repressed the expression of these genes; however, Cu(II) formed complex with the humic acid-like components, gradually weakening the inhibitive effect of these components. The promotion of low molecule organic matters dominated, resulting in a dynamic decline in the transfer efficiency. This study provides a new environmental contaminant treatment approach to eliminate the heavy metal-facilitated transfer of ARGs between bacteria.202234583164
8082190.9998Deciphering the toxic effects of antibiotics on denitrification: Process performance, microbial community and antibiotic resistance genes. The extensive application of antibiotics, and the occurrence and spread of antibiotic resistance genes (ARGs) shade health risks to human and animal. The long-term effects of sulfamethoxazole (SMX) and tetracycline (TC) on denitrification process were evaluated in this study, with the focus on nitrogen removal performance, microbial community and ARGs. Results showed that low-concentration SMX and TC (<0.2 mg L(-1)) initially caused a deterioration in nitrogen removal performance, while higher concentrations (0.4-20 mg L(-1)) of both antibiotics had no further inhibitory influences. The abundances of ARGs in both systems generally increased during the whole period, and most of them had significant correlations with intI1, especially efflux-pump genes. Castellaniella, which was the dominant genus under antibiotic pressure, might be potential resistant bacteria. These findings provide an insight into the toxic effects of different antibiotics on denitrification process, and guides future efforts to control antibiotics pollution in ecosystems.202032250829