Abundance of Cell-associated and Cell-free Antibiotic Resistance Genes in Two Wastewater Treatment Systems

为探究污水处理系统中抗生素抗性基因(ARGs)、 特别是胞外游离态ARGs的赋存特征,本研究选取生活污水处理系统和工业废水处理系统各一座,采用荧光定量PCR对细胞态及游离态ARGs丰度变化开展研究.在生活污水处理系统M中,进水sul、tetC、blaPSE-1和ermB这4种ARGs细胞态的绝对丰度均大幅高于游离态的绝对丰度,生物处理未对抗生素抗性菌(ARBs)产生富集效应;MBR的超滤膜有效削减了水中细胞态和游离态DNA,最终ARGs的总去除率为2.54~4.95 logs.在焦化废水处理系统C中,生物处理对携带sul的ARBs产生了富集效应,但游离态sul的相对丰度和绝对丰度均有所降低;其后混凝-砂滤工艺使水中细胞态和游离态sul的绝对丰度分别出现了下降和上升,游离态sul在总sul中的比例从生物处理出水中的0.05%,上升到混凝-砂滤出水中的1.33%,并在25℃ 恒温避光静置5d后进一步上升至9.31%.ARBs深度去除及残留细胞裂解,使污水处理系统出水中游离ARGs在总ARGs中的比例有所上升.游离态ARGs介导ARGs在污水处理系统出水受纳环境中的传播扩散风险有待后续研究进行深入评估.For revealing the characteristics of antibiotic resistance genes (ARGs) in wastewater treatment systems, real-time PCR was adopted to investigate the variation of abundances of cell-associated ARGs and cell-free ARGs, in a municipal wastewater treatment system (M for short) and a coking wastewater treatment system ( C for short). In system M, the absolute abundances of the cell-associated ARGs, sul , tetC, blaPSE- 1, and ermB, were much higher than those of the cell-free fractions in the influent. The biological treatment process did not enrich antibiotic resistance bacteria ( ARBs) and membrane filtration of the MBR effectively reduced both cell-associated and cell-free DNA in water. The total ARGs removal was 2. 54-4. 95 logs. In system C, the biological treatment process enriched the sul -carried ARBs; however, the relative and absolute abundances of cell-free sul were decreased. The succeeding process, coagulation-sand filtration, decreased the absolute abundance of cell-associated sul , but increased the absolute abundance of cell-free sul in water. The proportion of cell-free sul in total sul gene increased from 0. 05% in the biological treatment effluent to 1. 33% in the sand filtration effluent and further increased to 9. 31% after the effluent was kept at 25℃and at dark for five days. The ratio of cell-free ARGs to total ARGs increased with deep removal of ARBs and lysis of residual cells. The risk of ARG proliferation by cell-free DNA in the effluent needs further evaluation.国家自然科学基金项目93823-38303