摘要

      本研究将六座城市污水处理厂剩余活性污泥按其紧密结合程度的不同，分层成上清液、黏液、微键合胞外聚合物（LB-EPS）和紧密结合EPS（TB-EPS）四种胞外组分和一种胞内组分（颗粒）污泥微生物聚集并测定了7种抗生素抗性基因（sul-I、sul-II、tet-C、tet-X、blaTEM、mefA和cat）和1种流动基因（MGEs）（IntI-1）的丰度。胞外ARGs占总ARGs的0.1%-74.2%，胞外DNA与总DNA的比值仅为1.2%-4.2%，说明EPS是污泥中主要的ARGs库。sul-I、tet-C和mefA基因在LB-EPS、粘液和上清液中所占比例从0.5%到32.7%不等，具有最高的迁移率，这表明介导ARGs向环境迁移的风险增加。相比之下，污泥中TB-EPS中的小蠊所占比例为0.3%-34.9%，导致污泥的流动性有限。SulⅡ、tet-X、cat和IntI-1在细胞中所占比例约为82.6%-99.6%，流动性较差。本研究提出ARGs和MGEs具有不同的迁移率。在废水处理和污泥利用过程中，位于污泥最外层的污泥具有更高的移动性，有可能进入自然环境，从而增加可转移的风险。

       The present study stratified excess activated sludge from six municipal wastewater treatment plants into four extracellular fractions including supernatant, slime, slightly-bond extracellular polymeric substances (LB-EPS) and tightly-bond EPS (TB-EPS) and one intracellular fraction (pellet) according to their different degrees of tight binding to sludge microbial aggregates and determined the abundance of seven antibiotic resistance genes (ARGs) (sul-I, sul-II, tet-C, tet-X, blaTEM, mefA and cat) and one mobile genetic elements (MGEs) (IntI-1) in each fraction. Extracellular ARGs were found to make up 0.1% - 74.2% of total ARGs, while the ratio of extracellular DNA to total DNA was only 1.2% - 4.2%, implying that EPS was a major ARG reservoir in sewage sludge. The genes of sul-I, tet-C and mefA have the highest mobility owing to a large proportion ranging from 0.5% to 32.7% in the fractions of LB-EPS, slime and supernatant, which indicates an increased risk of mediating the transfer of ARGs to environment. Comparatively, the proportion of blaTEM in the TB-EPS of sludge accounted for 0.3%-34.9% and caused limited-mobility. Sul-II, tet-X and cat and IntI-1, made up approximately 82.6% - 99.6% proportion in the cells, and were thus less mobile. This study proposes that ARGs and MGEs can have different mobilities. Those located in the outermost layers of sludge have a higher mobility potential of propagation into the natural environment during wastewater treatment and sludge utilization, leading to an increased risk of transferability.

       https://linkinghub.elsevier.com/retrieve/pii/S0048-9697(19)34153-1