The Behavior And Correlations Of Antibiotic Resistance Genes And Microcvstins In Drinking Water Treatment Plants

Nowadays,environment resistance problems caused by the abuse of antibiotics have been increasingly drawn public attention,especially after the emergence of"super bug"in 2010.Contemporarily,the secondary pollution of Microcystins(MCs)arises from cyanobacterial blooms takes place in nature water bodies has also been a hot issue of global concern.In view of the environment hazad and health risk caused by these two pollutants,understanding and controlling the antibiotic resistance genes(ARGs)and MCs in drinking water supply systems have been the focus of relevant scientists,respectively.However,the bacterial characteristics and interactions between the two pollutants in case of the co-occurence conditions are still not been reported,which is of great significance for the scientific assessment of drinking water safety control.In this study,high-throughput quantitative real-time PCR,16S rRNA high-throughput sequencing and enzyme linked immunoserbent assay were respectively used to investigate ARGs,bacterial community and MCs in two drinking water treatment plants around South Taihu Lake.Based on the field research,the effect of MCs on the horizontal transfer of ARGs was studied in the laboratory,with the mechanism explored at the cellular and molecular levelsIt showed that conventional treatment processes didn’t captain effective removal abilities on ARGs,while post-ozone process greatly control the spread of ARBs.The correlation between activated carbon effluent and water plant effluent were confirmed,indicating the active carbon process actually affected the abundance and structure of ARGs in effluent.It was also found that the current washing back-washing method is not ideal for the removal of resistant bacteria.Conventional treatment processes had a certain effect on the production of microcystis,but not obviously on MCs.Activated carbon removed microcystins by adsorption mechanism,and the removal efficiency could reach up to 20.2%±1.5%However,with the redundant analysis,the concentration of microcystins and abundance of ARGs on activated carbon biofilm were significantly correlated.The result of conjugation transfer experiments showed that MC-LR was the most efficient in promoting conjugation transfer,which was 25.13 times than under natural conditions.The optimal concentration of MCs was consistent to that in drinking water environment with the 14.38 times promotion folds,which should be more valuedThe flow cytometry experiminet showed that microcystins produced oxidative stress by stimulating bacteria to produce reactive oxygen free radicals,which increased cell membrane permeability and facilitated the transfer of resistance genes to recipient bacteria.At the molecular level,microcystins affected conjugation transfer by regulating a series of gene systems,including increasing the expression of oxidative stress gene rpoS to regulate SOS responses;up-regulating the outer membrane protein encoding gene(ompA,ompF and ompC)to change the pore-forming process of cell membranes so that increased intercellular contact;down-regulating the global regulatory genes（korA,korB,trbA)to reduce the rejection of the junctional metastasis system.