摘要

      污水处理厂（WWTPs）是世界范围内保护人类和环境健康的有效屏障，但也被认为是抗生素抗性基因（ARGs）进入环境前的选择和或贮存者。关于污水处理厂作为“ARG选择因子”的教条认为，生物处理室（如活性污泥；AS）是单一的、人口稠密的生态系统，具有较高的水平基因转移。然而，最近的研究表明，污水处理厂的生物处理室可能与之前认为的抗生素耐药（AR）结果不同，其他工艺因素，如细菌分离和特定的废物来源，可能是ARGs释放到环境中的关键。在这里，我们将16srRNA宏基因组测序和高通量qPCR相结合，对西班牙污水网络中的微生物群落和ARG进行了表征，该网络包括社区（即非临床城市）和医院来源。与预期相反，在下游接受水中发现的ARG并非主要由AS生物固体（RAS）控制，而是更类似于原始废水来源。事实上，污水处理厂液相废水和RAS中的ARGs和微生物群落存在显著差异（Bray-Curtis差异指数 = 0.66    0.11），进水ARGs和直接通过污水处理厂的生物体的相应比例与RAS的关联性有限。相反，RAS中的ARG和有机体可能更多地由生物固体分离和生物物理特性（如絮凝作用）来定义，而不是ARG运输。这解释了为什么RAS的ARG丰度（47     4 ARG s）显著低于液相废水（104    5 ARGs）、下游水柱（135    4 ARGs）和河流沉积物（120      5 ARGs）（Tukey检验，p <0.001）。这些数据表明RAS和液相污水处理厂的废水可能反映了两个平行的生态系统，它们的ARG交换可能有限。因此，在污水处理厂中减少ARGs应更加注重从液相中去除细菌宿主，减少AR源，并可能进行消毒，以减少ARGs释放到环境中。

      Wastewater treatment plants (WWTPs) are an effective barrier in the protection of human and environment health around the world, although WWTPs also are suggested to be selectors and-or reservoirs of antibiotic resistance genes (ARGs) before entering the environment. The dogma about WWTPs as "ARG selectors" presumes that biotreatment compartments (e.g., activated sludge; AS) are single densely populated ecosystems with elevated horizontal gene transfer. However, recent work has suggested WWTP biotreatment compartments may be different than previously believed relative to antibiotic resistance (AR) fate, and other process factors, such as bacterial separation and specific waste sources, may be key to ARGs released to the environment. Here we combined 16S rRNA metagenomic sequencing and high-throughput qPCR to characterise microbial communities and ARGs across a wastewater network in Spain that includes both community (i.e., non-clinical urban) and hospital sources. Contrary to expectations, ARGs found in downstream receiving waters were not dominated by AS biosolids (RAS), but more resembled raw wastewater sources. In fact, ARGs and microbial communities in liquid-phase WWTP effluents and RAS were significantly different (Bray-Curtis dissimilarity index = 0.66 ± 0.11), with a consequential fraction of influent ARGs and organisms passing directly through the WWTP with limited association with RAS. Instead, ARGs and organisms in the RAS may be more defined by biosolids separation and biophysical traits, such as flocculation, rather than ARG carriage. This explains why RAS has significantly lower ARG richness (47 ± 4 ARGs) than liquid-phase effluents (104 ± 5 ARGs), and downstream water column (135 ± 4 ARGs) and river sediments (120 ± 5 ARGs) (Tukey's test, p < 0.001). These data suggest RAS and liquid-phase WWTP effluents may reflect two parallel ecosystems with potentially limited ARG exchange. As such, ARG mitigation in WWTPs should more focus on removing bacterial hosts from the liquid phase, AR source reduction, and possibly disinfection to reduce ARG releases to the environment.

       https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6650630/