摘要
      抗生素联合暴露对活性污泥系统氮去除、微生物群落组装和抗生素抗性基因增殖的影响是活性污泥系统中的一个热点。然而，目前尚不清楚历史上的抗生素应激如何影响微生物和ARGs对联合抗生素的后续反应。在本研究中，研究了不同剂量（0.005-30mg/L）的磺胺甲恶唑（SMX）和甲氧苄啶（TMP）联合污染对SMX或TMP应激遗留活性污泥的影响，以阐明抗生素遗留效应。在较高水平的联合暴露下，硝化活性受到抑制，但总氮去除率较高（～70%）。基于全面分类，过去抗生素应激的遗留效应对条件丰富类群（CAT）和条件稀有或丰富类群（CRAT）的群落组成有显著影响。稀有类群（RT）是微生物网络中的关键类群，中心属的反应也受到抗生素胁迫的影响。硝化细菌和基因被抗生素抑制，好氧反硝化细菌（假单胞菌、Thaurea和Hydrogenophaga）在高剂量下富集，关键反硝化基因（napA、nirK和norB）也富集。此外，94个ARG的出现和共同选择关系受到遗留效应的影响。同时，发现了一些共享宿主（如柠檬酸杆菌）和中枢ARG（如mdtD、mdtE和acrD）。总的来说，抗生素残留可能会影响活性污泥对联合抗生素的反应，并且在较高的暴露水平下，残留效应更强。
Abstract
The effect of combined antibiotics exposure on nitrogen removal, microbial community assembly and proliferation of antibiotics resistance genes (ARGs) is a hotspot in activated sludge system. However, it is unclear that how the historical antibiotic stress affects the subsequent responses of microbes and ARGs to combined antibiotics. In this study, the effects of combined sulfamethoxazole (SMX) and trimethoprim (TMP) pollution on activated sludge under legacy of SMX or TMP stress with different doses (0.005-30 mg/L) were investigated to clarify antibiotic legacy effects. Nitrification activity was inhibited under higher level of combined exposure but a high total nitrogen removal (∼70%) occurred. Based on the full-scale classification, the legacy effect of past antibiotic stress had a marked effect on community composition of conditionally abundant taxa (CAT) and conditionally rare or abundant taxa (CRAT). Rare taxa (RT) were the keystone taxa in the microbial network, and the responses of hub genera were also affected by the legacy of antibiotic stress. Nitrifying bacteria and genes were inhibited by the antibiotics and aerobic denitrifying bacteria (Pseudomonas, Thaurea and Hydrogenophaga) were enriched under legacy of high dose, as were the key denitrifying genes (napA, nirK and norB). Furthermore, the occurrences and co-selection relationship of 94 ARGs were affected by legacy effect. While, some shared hosts (eg., Citrobacter) and hub ARGs (eg., mdtD, mdtE and acrD) were identified. Overall, antibiotic legacy could affect responses of activated sludge to combined antibiotic and the legacy effect was stronger at higher exposure levels.

https://www.sciencedirect.com/science/article/abs/pii/S1001074222005526