Wastewater treatment plants (WWTPs) are important sources of antibiotic resistance genes (ARGs). Increasing attention has been paid to extracellular ARGs in cell-free form due to their horizontal gene transfer via transformation. However, the fate of the adsorbed form of extracellular ARGs that exist in extracellular polymeric substances (EPS) of activated sludge in WWTP remains largely unknown. Herein, seven EPS-associated ARGs along the anaerobic-anoxic-aerobic (AAO) process were quantified using quantitative polymerase chain reaction. Results show that the absolute abundances of EPS-associated ARGs were 0.69–4.52 logs higher than those of cell-free ARGs. There was no significant difference in the abundances of EPS-associated ARGs along the AAO process. Among these target genes, the abundances of EPS-associated sul genes were higher than those of EPS-associated tet and bla genes. Proteobacteria and Bacteroidetes were identified as the major secretors of EPS-associated ARGs, and they may play an important role in the proliferation of extracellular ARGs. Moreover, the transformation efficiencies of EPS-associated ARGs were 3.55–4.65 logs higher than those of cell-free ARGs, indicating that EPS-associated ARGs have higher environmental risks. These findings have advanced our understanding of EPS-associated ARGs and are useful for the control and risk assessment of ARGs in WWTPs.

污水处理厂 (WWTPs) 是抗生素抗性基因 (ARGs) 的重要来源。由于它们通过转化进行水平基因转移，因此越来越关注无细胞形式的细胞外 ARG。然而，存在于 WWTP 活性污泥的胞外聚合物 (EPS) 中的胞外 ARGs 的吸附形式的命运仍然很大程度上未知。在此，使用定量聚合酶链反应对厌氧-缺氧-好氧 (AAO) 过程中的七个 EPS 相关 ARG 进行了量化。结果表明，EPS 相关 ARGs 的绝对丰度比无细胞 ARGs 高 0.69-4.52 个对数。在 AAO 过程中与 EPS 相关的 ARG 的丰度没有显着差异。在这些靶基因中，EPS 相关sul的丰度基因高于EPS相关的tet和bla基因。Proteobacteria和Bacteroidetes被确定为 EPS 相关 ARGs 的主要分泌者，它们可能在细胞外 ARGs 的增殖中起重要作用。此外，EPS相关ARGs的转化效率比无细胞ARGs高3.55-4.65 log，表明EPS相关ARGs具有更高的环境风险。这些发现加深了我们对 EPS 相关 ARGs 的理解，并有助于 WWTPs 中 ARGs 的控制和风险评估。