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[Display omitted] • Applied voltage improved performances of AnEMBR in treating high CTC wastewater. • Applied voltage greatly reduced ARGs abundances in effluent of AnEMBR. • HGT and microbial community shift contributed to ARGs proliferation in sludge. • Enriched tetracycline degradation gene at 0.7 V reduced ARGs 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 CH 4 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 CH 4 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. [ABSTRACT FROM AUTHOR]

Antibiotic resistance has become a global public health problem. Recently, various environmental pollutants have been reported to induce the proliferation of antibiotic resistance. However, the impact of multiple pollutants (e.g., heavy metals and antibiotics), which more frequently occur in practical environments, is poorly understood. Herein, one widely distributed heavy metal (Ag+) and one frequently detected antibiotic (tetracycline) were chosen to investigate their coexisting effect on the proliferation of antibiotic resistance in the activated sludge system. Results show that the co-occurrence of Ag+ and tetracycline at environmentally relevant concentrations exhibited no distinct inhibition in reactor performances. However, they inhibited the respiratory activity by 42%, destroyed the membrane structure by 218%, and increased membrane permeability by 29% compared with the blank control bioreactor. Moreover, the relative abundances of target antibiotic resistance genes (ARGs) (e.g., tetA , bla TEM-1 , and sulII) in effluent after exposure of coexisting Ag+ and tetracycline were increased by 92–1983% compared with those in control reactor, which were 1.1–4.3 folds higher than the sum of the sole ones. These were possibly attributed to the enrichments of antibiotic-resistant bacteria. The results would illumine the coexisting effect of heavy metals and antibiotics on the dissemination of ARGs in activated sludge system. [Display omitted] • Coexisting Ag+ and TC did not inhibit the bioreactor performance. • Coexisting Ag+ and TC caused more microbial damage. • Coexisting Ag+ and TC enriched ARGs in sludge and effluent. • Coexisting Ag+ and TC enriched heavy metal and antibiotic-resistant bacteria. [ABSTRACT FROM AUTHOR]

Earthworms have shown their effectiveness in reducing the abundances of antibiotic resistance genes (ARGs) from solid waste. However, the mechanisms of the reduced ARGs by earthworm and whether the solid waste would affect the ARGs profile in earthworm gut were poorly understood. Herein, the patterns of ARGs and microbial communities in digested sludge-amended soil and earthworm gut after 80-day cultivation were investigated. Results show that the enrichment of ARGs (e.g., tet A, tet Q, and sul II) in soil caused by digested sludge-amendment was temporary and would recover to their original levels before amendment. In addition, earthworms could contribute to the further reduction of ARG abundances, which was mainly attributed to their gut digestion via shifting the microbial community (e.g., attenuating the anaerobes). However, the amended soil could significantly increase ARGs abundance in the earthworm gut, which may enhance the potential risk of ARGs spread via the food chain. These findings may provide a new sight on the control of ARGs occurrence and dissemination in sludge-amended soil ecosystem with consideration of earthworms. [Display omitted] • ARGs enrichment in soil by digested sewage sludge amendment was temporary. • Earthworms contributed to further reduction in ARG abundances in amended soil. • Reduced ARGs were attributed to microbial community shift. • Digested sludge-amended soil increased ARG abundances in earthworm gut. [ABSTRACT FROM AUTHOR]

Anaerobic biological treatment technologies are one of the major hotspots of antibiotic resistance genes (ARGs). Previous studies have applied the electrochemical process to improve biogas production, however, it was challenged that high voltages might promote membrane permeability and reactive oxygen species overproduction to promote ARGs proliferation. Herein, the biogas production and ARGs proliferation in an anaerobic electrochemical membrane bioreactor (AnEMBR) were investigated at the gradient voltages of 0–0.9 V. Results show the reactor performances (average CH 4 production and current generation) were distinctly improved with the increase of applied voltage, and reached the optimum at 0.9 V. However, long-term application (>30 day) of 0.9 V deteriorated the reactor performances. Meanwhile, the relative abundances of most target ARGs in the supernatant and effluent of AnEMBR at 0.9 V increased by 0.68–1.55 and 0.42–1.26 logs compared to those before applying voltage, respectively. After disconnecting the circuit, these ARGs abundances all decreased to the original level. Significant correlations between intlI and ARGs (e.g., tetA , tetQ , sulI , and sulII) were observed, indicating horizontal gene transfer may contribute to the increased ARGs. Moreover, the shift of microbial communities caused by the applied voltage enriched potential ARGs-hosts (e.g., Tolumonas), contributing to the proliferation of ARGs. [Display omitted] • Introducing low voltage greatly improved the biogas production in AnEMBR. • Long-term application of high voltage (0.9 V) deteriorated AnEMBR performance. • Applying voltage shifted the microbial community in AnEMBR. • High voltage application increased ARGs abundances in AnEMBR. • Horizontal gene transfer and microbial community shift led to ARG proliferation. [ABSTRACT FROM AUTHOR]

Fish-associated antibiotic resistance genes (ARGs) have attracted increasing attention due to their potential risks to human beings via the food chain. However, data are scarce regarding the antibiotic resistance in fish themselves. Herein, the antibiotic resistance genes (ARGs) were assessed in the gut of four major Chinese freshwater carp (i.e., silver carp, grass carp, bighead carp, and crucian carp) from food retail markets. Results show that the abundances of target ARGs (e.g., tetA , tetO , tetQ , tetW , sulI , sulII , and bla TEM-1) and class 1 integrase (intI1) were in the range 9.4 × 10−6 - 1.6 × 10−1 and 6.7 × 10−5 - 5.2 × 10−2 gene copies per 16S rRNA gene, respectively. The sulI , sulII , and tetQ strongly correlated with silver and mercury resistance genes (e.g., silE and merR). The microbial taxa of fish gut could be partly separated among retail markets based on the PCA analysis. About 15.0% of the OTUs in fish gut were shared and 74.5% of the shared OTUs were identified as Acidobacteria , Bacteroidetes , Chloroflexi , Cyanobacteria , Firmicutes , and Proteobacteria. These phyla may constitute the core microbiota in the guts of the four Chinese freshwater carp. The possible ARG hosts were revealed based on the network analysis, and the presence of pathogen-associated resistant genera in fish gut highlights the need to fully understand their potential human health risks. Image 1 • The abundances of ARGs were quantified in the gut of Chinese freshwater carp. • SulI , sulII , and tetQ were strongly correlated with silE and merR in fish gut. • Microbial taxa of fish gut were different among retail markets. • Some pathogenic genera were observed in the gut of fish. This study investigated the abundances of ARGs and microbiota in fish gut and provided new insight on ARGs pollution in Chinese four major freshwater carp. [ABSTRACT FROM AUTHOR]

The prevalence of antibiotic resistance genes (ARGs) in municipal wastewater treatment plants (MWTPs) has emerged as a significant environmental concern. Despite advanced treatment processes, high levels of ARGs persist in the secondary effluent from MWTPs, posing ongoing environmental risks. This study explores the potential of gamma-ray irradiation as a novel approach for sterilizing antibiotic-resistant bacteria (ARB) and reducing ARGs in MWTP secondary effluent. Our findings reveal that gamma-ray irradiation at an absorbed dose of 1.6 kGy effectively deactivates all culturable bacteria, with no subsequent revival observed after exposure to 6.4 kGy and a 96-h incubation in darkness at room temperature. The removal efficiencies for a range of ARGs, including tetO , tetA , bla TEM-1 , sulI , sulII , and tetW , were up to 90.5% with a 25.6 kGy absorbed dose. No resurgence of ARGs was detected after irradiation. Additionally, this study demonstrates a considerable reduction in the abundances of extracellular ARGs, with the transformation efficiencies of extracellular tetracycline and sulfadiazine resistance genes decreasing by 56.3–81.8% after 25.6 kGy irradiation. These results highlight the effectiveness of gamma-ray irradiation as an advanced and promising method for ARB sterilization and ARG reduction in the secondary effluent of MWTPs, offering a potential pathway to mitigate environmental risks associated with antibiotic resistance. [Display omitted] • Gamma-ray irradiation reduced the abundances of ARGs by 1.69-3.69 logs. • Over 99% of VBNC bacteria were removed by Gamma-ray irradiation. • Gamma-ray irradiation reduced the transformation ability of released eARGs. • Direct action of irradiation was the major contributor to ARGs degradation. • Gamma-ray irradiation treatment improved the effluent quality. [ABSTRACT FROM AUTHOR]

Antibiotic resistance has been regarded as a global concern and biological wastewater treatment plants (WWTPs) are ideal hotbeds for the emergence and propagation of antibiotic resistance genes (ARGs). Extracellular polymeric substances (EPS), one of the primary components of activated sludge, might affect the distribution of extracellular ARGs in supernatant and EPS matrix, and thus alter their uptake potential by microbial cells. Herein, the presence and significance of EPS-associated ARGs in activated sludge from four WWTPs were assessed. Seven typical ARGs (sulI , sulII , bla TEM-1 , tetA , tetO , tetQ , tetW) and class I integron (intI1) in EPS-associated, cell-free, and intracellular DNA were quantified. Results show that the absolute abundances of EPS-associated, cell-free, and intracellular ARGs were 5.90 × 106–6.45 × 109, 5.53 × 104–4.58 × 106, and 2.68 × 108–1.79 × 1011 copies/g-volatile suspended solids, respectively. The absolute abundances of EPS-associated ARGs were 0.2–4.6 orders of magnitude higher than those of the corresponding cell-free ARGs. Considering the higher DNA contents in EPS, the transformation abilities of EPS-associated ARGs were 3.3–236.3 folds higher than those of cell-free ARGs. Therefore, EPS-associated ARGs are an important source of extracellular ARGs, and it may play a crucial role in horizontal gene transfer via transformation in WWTPs. ga1 • Presence and significance of EPS-associated ARGs in activated sludge were assessed. • EPS-associated ARG absolute abundances were 0.2–4.6 logs higher than cell-free ARGs. • EPS-associated ARGs had higher transformation potential than cell-free ARGs. • EPS-associated ARGs are an important source of extracellular ARGs. [ABSTRACT FROM AUTHOR]