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Metagenomic insight into the enrichment of antibiotic resistance genes in activated sludge upon exposure to nanoplastics
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Researchers used metagenomic analysis to show that polystyrene nanoplastics at environmentally relevant concentrations increased antibiotic resistance genes in activated sludge by up to 59%, primarily by promoting horizontal gene transfer and enriching Proteobacteria host populations — raising concerns about nanoplastic-driven spread of antibiotic resistance in wastewater treatment.
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.
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Metagenomic Analysis Reveals the Effects of Microplastics on Antibiotic Resistance Genes in Sludge Anaerobic Digestion
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Researchers used metagenomic analysis to study how microplastics in sewage sludge affect the spread of antibiotic resistance genes during anaerobic digestion. They found that microplastics increased antibiotic resistance gene levels by up to 30 percent, with polyethylene having the strongest effect, and also boosted the mobile genetic elements that help resistance genes spread between bacteria. The findings raise concerns about microplastics facilitating the spread of antibiotic resistance through wastewater treatment systems.
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Researchers studied how aged and non-aged nanoplastics from both manufactured and environmentally degraded polystyrene affect the spread of antibiotic resistance genes during sewage sludge treatment. They found that higher concentrations of nanoplastics inhibited the treatment process and increased the abundance of antibiotic resistance genes, with environmentally degraded particles having a stronger effect due to their altered surface properties. The study raises concerns that nanoplastic pollution in sewage systems may be contributing to the spread of antibiotic resistance.
Metagenomic analysis reveals the responses of microbial communities and nitrogen metabolic pathways to polystyrene micro(nano)plastics in activated sludge systems
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Scientists used genetic analysis to study how polystyrene micro- and nanoplastics disrupt the bacteria that process nitrogen in wastewater treatment systems. At high concentrations, the plastics reduced nitrogen removal efficiency by up to 30% by generating harmful reactive oxygen species that damaged key microbial processes. This is concerning because less effective wastewater treatment means more pollutants, including microplastics themselves, could end up in waterways.
Impact of polystyrene nanoplastics on primary sludge fermentation under acidic and alkaline conditions: Significance of antibiotic resistance genes
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Researchers studied how polystyrene nanoplastics affect the fermentation of sewage sludge at different pH levels. They found that low doses stimulated hydrogen gas production while higher concentrations suppressed it, and that nanoplastic exposure promoted the spread of antibiotic resistance genes in the microbial community. The findings raise concerns about nanoplastics in wastewater systems potentially contributing to the broader problem of antibiotic resistance.
Microplastics as hubs enriching antibiotic-resistant bacteria and pathogens in municipal activated sludge
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Researchers demonstrated that microplastics in municipal wastewater treatment plants act as "hubs," selectively concentrating antibiotic-resistant bacteria and pathogens in their surface biofilms, with antibiotic-resistance genes enriched up to 4.5-fold compared to sand particles — raising concerns about microplastics spreading drug-resistant microbes into the environment.
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