Microplastics (MPs) and antibiotics co-occur widely in the environment and pose combined risk to microbial communities. The present study investigated the effects of erythromycin on biofilm formation and resistance mutation of a model bacterium, , on the surface of pristine and UV-aged polystyrene (PS) MPs sized 1–2 mm. The properties of UV-aged PS were significantly altered compared to pristine PS, with notable increases in specific surface area, carbonyl index, hydrophilicity, and hydroxyl radical content. Importantly, the adsorption capacity of UV-aged PS towards erythromycin was approximately 8-fold higher than that of pristine PS. Biofilms colonizing on UV-aged PS had a greater cell count (5.6 × 10 CFU mg) and a higher frequency of resistance mutation (1.0 × 10) than those on pristine PS (1.4 × 10 CFU mg and 1.4 × 10, respectively). Moreover, erythromycin at 0.1 and 1.0 mg significantly ( < 0.05) promoted the formation and resistance mutation of biofilm on both pristine and UV-aged PS. DNA sequencing results confirmed that the biofilm resistance was attributed to point mutations in segment of the bacterial genome. qPCR results demonstrated that both UV aging and erythromycin repressed the expression levels of a global regulator in biofilm bacteria, as well as two DNA mismatch repair genes and , which was likely to contribute to increased resistance mutation frequency.

中文翻译：

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红霉素对原始和紫外线老化聚苯乙烯微塑料上生物膜形成和大肠杆菌抗性突变的影响

微塑料 (MP) 和抗生素在环境中广泛共存，对微生物群落构成综合风险。本研究调查了红霉素对原始和紫外线老化聚苯乙烯 (PS) MP 尺寸 1-2 毫米表面上的生物膜形成和模型细菌耐药性突变的影响。与原始PS相比，经紫外线老化的PS的性能发生了显着改变，比表面积、羰基指数、亲水性和羟基自由基含量显着增加。重要的是，紫外线老化的 PS 对红霉素的吸附能力比原始 PS 大约高 8 倍。与原始 PS 上的生物膜（分别为 1.4 × 10 CFU mg 和 1.4 × 10）相比，在 UV 老化 PS 上定殖的生物膜具有更多的细胞计数（5.6 × 10 CFU mg）和更高的抗性突变频率（1.0 × 10）。此外，0.1 和 1.0 mg 的红霉素显着（< 0.05）促进原始和紫外线老化 PS 上生物膜的形成和抗性突变。 DNA测序结果证实，生物膜耐药性归因于细菌基因组片段的点突变。 qPCR 结果表明，紫外线老化和红霉素都会抑制生物膜细菌中全局调节因子以及两个 DNA 错配修复基因 和 的表达水平，这可能导致耐药突变频率增加。