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Effects of aging of polyethylene microplastics and polystyrene nanoplastics on antibiotic resistance gene transfer during primary sludge fermentation
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This study found that aged (weathered) microplastics and nanoplastics promoted the spread of antibiotic resistance genes during sewage sludge treatment more than fresh plastics did. The weathering process changed the surface properties of the plastics, making them better carriers for drug-resistant bacteria and their genes. This is concerning because sludge from treatment plants is often applied to farmland, potentially spreading antibiotic resistance through soil and into the food supply.
The increasing presence of nano and microplastics (NPs/MPs) in wastewater treatment plants and their inevitable accumulation in the sludge has raised serious concerns in recent years. This study investigated the effects of pristine and aged polyethylene microplastics (PEMPs), polystyrene nanoplastics (PsNPs), and their mixtures on the primary sludge fermentation process. Pristine MPs/NPs (150 μg/L and 2 g/L for PsNPs and PEMPs, respectively) underwent two weeks of weathering in the presence of humic and alginic acids. The results from a batch fermentation experiment (15 days, pH 10) revealed that the exposure to aged PEMPs/PsNPs experienced greater VFA production than pristine samples. Notably, the aged PEMPs/PsNPs mixture showed a 23.12% increase in VFA production over the pristine mixture. The relative abundance and total concentration of antibiotic resistance genes (ARGs) increased in all PEMPs/PsNPs batches compared to the control, with the most significant rise in total ARGs observed in the aged PEMPs sample. Aged PEMPs exhibited a 26.22-fold increase in tetA genes, while aged mix samples showed a 19.68-fold increase in tetM genes compared to their pristine counterparts. Both pristine and aged PEMPs/PsNPs, particularly the aged PEMPs adversely affected the microbial communities at the genus level and altered the microbial structure. Microbial richness and diversity were enhanced in samples exposed to pristine PEMPs/PsNPs and aged PsNPs but decreased in aged PEMPs and in the aged mixture group, suggesting a negative impact of aged polyethylene microplastics on microbial communities. Correlation analysis suggested that phyla Planctomycetes, Proteobacteria, and TM7 are potential hosts of ARGs. These findings manifest the substantial effects of aged nano/microplastics compared to their pristine forms, emphasizing the complex interplay between various forms of PEMPs/PsNPs and microbial dynamics in sludge fermentation processes.
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Impact of aging of primary and secondary polystyrene nanoplastics on the transmission of antibiotic resistance genes in anaerobic digestion
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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.
Aging attenuates threat: how moderate aging of microplastics suppresses antibiotic resistance gene proliferation during sludge anaerobic digestion
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Researchers examined how the degree of weathering of polyethylene and polypropylene microplastics affects their tendency to promote antibiotic resistance gene spread during sewage sludge digestion, and found a counterintuitive U-shaped relationship: moderately aged plastics actually suppressed resistance gene proliferation by up to 50% compared to fresh plastics, while more heavily aged plastics saw the effect bounce back. The mechanism involves weathering altering how microplastics affect microbial stress responses and gene transfer pathways. The findings highlight that the environmental history of microplastics matters when assessing their biological risks.
Microplastics 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
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This study found that microplastics in sewage sludge promote the spread of antibiotic resistance genes, which make bacteria harder to treat with antibiotics. Microplastics provided a surface for resistant bacteria to grow and helped them share resistance genes with other bacteria. The more microplastics present, the more antibiotic resistance spread, raising concerns about how plastic pollution in wastewater could contribute to the growing antibiotic resistance crisis.
Aged Microplastics and Antibiotic Resistance Genes: A Review of Aging Effects on Their Interactions
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This review explores how the aging of microplastics in the environment affects their ability to harbor antibiotic resistance genes. Researchers found that weathering processes like sunlight exposure increase the surface area of microplastics and generate reactive oxygen species, both of which can enhance the uptake and transfer of resistance genes among bacteria. The findings suggest that aged microplastics in the environment may be more effective at spreading antibiotic resistance than fresh ones.
Microplastics act as vectors for antibiotic resistance genes in landfill leachate: The enhanced roles of the long-term aging process
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This study examined whether the aging of microplastics in aquatic environments influences their role as vectors for antibiotic resistance genes (ARGs). Aged microplastics showed different ARG enrichment patterns on their surfaces compared to pristine particles, suggesting that weathering changes the capacity of plastic debris to accumulate and spread antibiotic resistance.
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