基于宏基因组学解析不同污水处理系统的耐药基因组分布特征和传播机制

Distribution Characteristics and Transmission Mechanism of Antibiotic Resistome in Different Wastewater Treatment Systems Based on Metagenomic Analysis

污水处理厂是向水环境中传播抗生素抗性基因(antibiotic resistance genes,ARGs)的热点。与城镇污水相比,工业园区废水成分复杂、污染物浓度高,更有利于ARGs的增殖和扩散。为探究不同类型废水环境的ARGs组成特征和潜在的传播风险,采用宏基因组学技术分别对城镇生活污水处理系统(W1-SD)、工业园区废水处理系统(W1-SI)和2个城镇综合污水处理系统(W2-LH1和W2-LH2)进行取样调查。结果显示,多重耐药类、磺胺类、氨基糖苷类和杆菌肽类抗性基因是废水环境中的主要耐药类型,Ⅰ型整合子、转座酶基因等可移动遗传元件(MGEs)对sul1、aadA和ereA等基因亚型的增殖扩散发挥了关键作用,通过序列分型发现质粒型ARGs的相对丰度更高,尤其是在进水样品中,氨基糖苷类和磺胺类等抗性基因是主要的质粒型ARGs;污水处理过程削减了ARGs多样性,且经过二次沉淀工艺,ARGs丰度均明显降低,但在W1-SI和W2-LH2中,后续的深度处理工艺又使ARGs丰度升高;与城镇污水处理系统相比,W1-SI的ARGs组成更为稳定,最终排水中富集了较高丰度的质粒型ARGs,同时识别到了高频率的潜在水平基因转移事件和2条携带多种抗性基因的重叠群序列(contigs),表明工业园区废水排放具有更高的ARGs传播风险。本研究丰富了不同类型废水环境耐药基因组的已有认知,为有效管控废水排放特别是工业园区废水排放的健康风险提供了科学依据。

Wastewater treatment plants(WWTPs)are hotspots for the spread of antibiotic resistance genes(ARGs)into the aquatic environment.Compared with domestic wastewater,wastewater from industrial parks has complex composition and high pollutant concentration,which may be more conducive to the proliferation and diffusion of ARGs.In order to explore the composition characteristics of ARGs in different types of WWTPs and their potential transmission risks,metagenomics was used to investigate the antibiotic resistome in a domestic WWTP(W1-SD),an industrial WWTP(W1-SI),and two integrated WWTPs(W2-LH1 and W2-LH2).The results showed that multidrug,sulfonamide,aminoglycoside and bacitracin resistance genes were the main ARG types in the WWTPs.Mobile genetic elements(MGEs)such as typeⅠintegron and transposase genes played key roles in the proliferation and diffusion of ARG subtypes such as sul1,aadA,and ereA.Sequence typing showed that the relative abundance of plasmid-borne ARGs was higher than other types of sequences,especially in the influent samples,and aminoglycosides and sulfonamides resistance genes were the main plasmid-borne ARGs.The diversity of ARGs was reduced in the wastewater treatment process,and the abundance of ARGs decreased significantly after secondary precipitation.However,in W1-SI and W2-LH2,the abundance of ARGs increased after advanced treatment.Compared with the domestic wastewater treatment system,the ARGs composition of W1-SI was more stable.A higher abundance of plasmid-borne ARGs was enriched in the final effluents.Meanwhile,a high frequency of potential horizontal gene transfer events and two contigs carrying multiple resistance genes were identified.The results indicated that wastewater discharge from the industrial parks had a higher risk of ARGs transmission than urban area.This study enriches the existing knowledge of antibiotic resistome in different types of WWTPs,and provides a scientific basis for the health risk management of wastewater discharge,especially in industrial parks.