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Biodegradable Microplastics Increase the Health Risks of Antibiotic Resistance Genes in Eutrophic Urban Lake
Summary
Researchers conducted an in-situ experiment in an urban lake comparing how biodegradable and conventional plastics accumulate antibiotic resistance genes on their surfaces. They found that biodegradable polymers like PBS and PLA harbored significantly more resistance genes than conventional polystyrene, and that bacterial communities on all plastics differed markedly from those in the surrounding water. The study suggests that biodegradable microplastics may actually pose higher health risks by serving as hotspots for antibiotic resistance in polluted freshwater environments.
Urban lakes are active interfaces between human activity and microbes, yet the health risks associated with antibiotic resistance genes (ARGs) on plastisphere biofilms are not well understood. An in-situ colonization experiment was conducted in East Lake, a eutrophic urban lake, using two biodegradable polymers (polybutylene succinate, PBS; polylactic acid, PLA) and two conventional polymers (polyvinyl chloride, PVC; polystyrene, PS). The bacterial communities, ARGs, and mobile genetic elements (MGEs), and a risk weighted index were analyzed based on the metagenomic data. Biodegradable PBS with higher hydrophilicity was found to be easier to be colonized. Plastisphere communities were compositionally distinct from lake water and showed higher diversity, with Pseudomonadota dominating plastics while Cyanobacteriota dominated water, indicating strong polymer specific selection. PBS and PLA supported greater detected number and relative abundance of ARGs than water, whereas PS showed the lowest relative abundance among plastics. In terms of subtype richness, β-lactam resistance genes were the most diverse (89 subtypes, 31.3% of all ARG subtypes). While, bacitracin resistance genes accounted for the largest composition in terms of relative abundance, followed by multidrug resistance genes. MGE compositions were also polymer dependent, and total MGE abundance was higher on PBS and PVC than in water, while PS was even lower than water. ARG hosts shifted toward taxa of concern, with marked enrichment of multidrug resistance bearing Pseudomonadota on microplastics compared with water. The risk weighted index separated polymers, with biodegradable microplastics showing risks comparable to or exceeding PVC and higher than PS. Therefore, these patterns indicate greater mobility potential and stronger pathogenic host associations within biodegradable plastisphere communities, which should be pay more attention in the urban lake management for human health.