Antibiotic resistance genes (ARGs) in activated sludge include intracellular ARGs (iARGs) and extracellular ARGs (eARGs), both of which are recognized as emerging pollutants. While the activated sludge process has been commonly considered for treating wastewater contaminated with radionuclide, the effects and mechanisms of radioactive heavy metals on the fate of iARGs and eARGs (i/e-ARGs) in activated sludge are largely elusive. Here, the distribution, mobility, and hosts of i/e-ARGs in activated sludge during environmental concentrations (50 μg/L and 5000 μg/L) of radioactive uranium (U) stress were explored via metagenomics. The results revealed that the total relative abundance of iARGs and eARGs decreased by 11.62% and 10.41%, respectively, after 90 days of 50 μg/L of U treatment. In contrast, both i/e-multi- and tetracycline ARGs remarkably increased after being exposed to 5000 μg/L of U. Additionally, exposure to 5000 μg/L of U triggered notable decrease in i/e-insertion sequences and plasmids abundance, but significantly enriched i/e-integrons (p < 0.05). Partial least squares pathway modelling indicated that the prevalence of iARGs and eARGs in activated sludge was primarily driven by bacterial hosts and functional genes, respectively. Our findings revealed the dichotomous variation landscape and mechanisms of i/e-ARGs dynamics in activated sludge during U exposure, offering valuable insights for controlling ARGs risk during radioactive wastewater treatment.

中文翻译：

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铀在调节活性污泥细胞内和细胞外抗生素抗性基因中的二分法作用的宏基因组分析


活性污泥中的抗生素耐药基因 （ARG） 包括细胞内 ARG （iARG） 和细胞外 ARG （eARG），这两种基因都被认为是新兴污染物。虽然活性污泥工艺通常被认为用于处理受放射性核素污染的废水，但放射性重金属对活性污泥中 iARG 和 eARG （I/E-ARG） 命运的影响和机制在很大程度上是难以捉摸的。在这里，通过宏基因组学探讨了在放射性铀 （U） 应激环境浓度（50 μg/L 和 5000 μg/L）期间活性污泥中 i/e-ARGs 的分布、迁移率和宿主。结果显示，50 μg/L U 处理 90 d 后，iARGs 和 eARGs 的总相对丰度分别下降了 11.62% 和 10.41%。相比之下，i/e-多环素和四环素 ARGs 在暴露于 5000 μg/L 的 U 后均显著增加。此外，暴露于 5000 μg/L 的 U 导致 i/e 插入序列和质粒丰度的显着降低，但 i/e 整合子显著富集 （p < 0.05）。偏最小二乘通路模型表明，活性污泥中 iARGs 和 eARGs 的普遍性分别主要由细菌宿主和功能基因驱动。我们的研究结果揭示了 U 暴露期间活性污泥中 i/e-ARGs 动力学的二分变化景观和机制，为控制放射性废水处理过程中的 ARGs 风险提供了有价值的见解。