摘要
      抗生素的共同暴露对废水处理厂的抗生素抗性基因（ARGs）和微生物群落聚集具有重要影响。然而，目前尚不清楚历史抗生素暴露压力的差异是否可以决定微生物和ARGs对联合抗生素的反应。通过选择高浓度（30mg·L-1）的磺胺甲恶唑（SMX）和甲氧苄啶（TMP）作为历史暴露应激条件，在短期实验中探讨了SMX和TMP联合污染对ARGs、细菌群落及其相互作用的影响。基于高通量定量PCR，共检测到13个ARGs，绝对丰度为2.21-5.42拷贝·μL-1（对数，DNA，下同）。其中，sul2、ermB、mefA和tetM-01是样本中的主要亚型，绝对丰度在2.95至5.40拷贝·μL-1之间。SMX和TMP的联合污染可能导致ARGs和可移动遗传元件（MGEs）的富集；然而，它们对每种亚型的影响是不同的，SMX的历史遗留效应高于TMP。在不同的暴露历史下，ARG之间存在共现和共排斥模式。此外，MGEs（尤其是intI-1）与磺酰胺类药物（sul1和sul2）、四环素类药物[tet（32）]和大环内酯类林可酰胺链脲菌素（MLSB）抗性基因（ermB）显著相关。在对微生物进行全面分类的基础上，发现不同类群的微生物群落结构对组合污染的反应不同，条件丰富类群（CAT）明显富集。Thauera属、假黄单胞菌属和副球菌属是主要的耐药菌属。此外，通过网络分析，共鉴定了31个ARGs的潜在宿主，这些宿主以条件稀有类群（CRT）为主。特别是Candidatus_Alysionsphaera和Fusibacter与大多数ARGs呈正相关，它们是常见的保护宿主。重要的是，一些稀有属（RT、Varibacter、Aeromonas、Cloacibacterium等）是转座子IS613的潜在宿主，其在ARGs的增殖和传播中发挥了重要作用。总之，本研究揭示了历史抗生素应激对ARGs及其宿主的遗留影响，为减少污水处理厂ARGs污染提供了新的思路和理论依据。
Abstract 
The co-exposure of antibiotics has important effects on antibiotic resistance genes (ARGs) and microbial community aggregation in wastewater treatment plants (WWTPs). However, it is unclear whether differences in historical antibiotic exposure stress can determine responses of microbes and ARGs to combined antibiotics. By selecting a high concentration (30 mg·L-1) of sulfamethoxazole (SMX) and trimethoprim (TMP) as historical exposure stress conditions, the effects of SMX and TMP-combined pollution on ARGs, bacterial communities, and their interactions were explored in short-term experiments. Based on high-throughput quantitative PCR, a total of 13 ARGs were detected, and the absolute abundance was 2.21-5.42 copies·μL-1 (logarithm, DNA, the same below). Among them, sul2, ermB, mefA, and tetM-01 were the main subtypes in the samples, and the absolute abundance was between 2.95 and 5.40 copies·μL-1. The combined contamination of SMX and TMP could cause the enrichment of ARGs and mobile genetic elements (MGEs); however, their effects on each subtype were different, and the historical legacy effect of SMX was higher than that of TMP. Under the different exposure histories, the co-occurrence and co-exclusion patterns existed between ARGs. Moreover, MGEs (especially intI-1) were significantly correlated with sulfonamides (sul1 and sul2), tetracyclines[tet(32)], and macrolide-lincosamide-streptogramin (MLSB) resistance genes (ermB). Based on the full-scale classification of microorganisms, it was found that the microbial community structure of various groups responded differently to combined pollution, and the conditionally abundant taxa (CAT) were obviously enriched. Thauera, Pseudoxanthomonas, and Paracoccus were the dominant resistant bacterial genera. Furthermore, a total of 31 potential hosts of ARGs were identified with network analysis, which were dominated with conditionally rare taxa (CRT). Particularly, Candidatus_Alysiosphaera and Fusibacter were positively correlated with most of the ARGs, being the common protentional hosts. Importantly, some rare genera (RT, Variibacter, Aeromonas, Cloacibacterium, etc.) were potential hosts of transposon IS613, which played an important role in the proliferation and spread of ARGs. In conclusion, this study revealed the legacy effects of historical antibiotic stress on ARGs and their hosts, which could provide new ideas and theoretical basis for reducing ARGs pollution in WWTPs.

https://europepmc.org/article/med/36224139