Co-occurrence Of CrAssphage And Antibiotic Resistance Genes In Agricultural Soils Of The Yangtze River Delta

Human intestinal bacteria-specific phage crAssphage is strongly correlated with the occurrence of antibiotic resistance genes(ARGs)in environments,which can potentially indicate ARGs contamination,and its indicator effect requires validation by analyzing large-scale environmental data.This thesis investigated the occurrence and abundances of crAssphage and typical ARGs in farmland soils in the Yangtze River Delta and explored their co-occurrence network and potential influencing factors.The outcomes provided theoretical support for the early warning and control of farmland soil ARGs pollution.The main findings are as follows:(1)The relative abundance of total ARGs was 2.26×10^-4?1.16×10^-1 copies/16S r RNA copies in agricultural soils in the Yangtze River Delta,and the average concentrations of tetracycline,quinolone and sulfonamide antibiotics were 27.03,12.48and 3.25 ng/g dry weight soil,respectively.(2)The detection rate of crAssphage in agricultural soils was 73.8%,mainly distributed along the Yangtze River,in the west bank of Lake Tai and in southern Zhejiang;the absolute abundances of crAssphage in all samples ranged from limit of detection to 7.46×10⁵ copies/g,which were affected by regional sewage treatment capacity and population density.High sewage treatment capacity could effectively reduce crAssphage in farmland soils.(3)The abundance of crAssphage was significantly positively correlated with ARGs in farmland soils,especially the tetracycline resistance gene tet W(rho=0.55,p<0.01).As the abundance of crAssphage increased,the frequency of coexisting ARGs also increased.When the relative abundance of cr Asshage was greater than 4.94×10^-4copies/16S r RNA copies,more than three ARGs could be detected with total relative abundance of ARGs above 3.95×10^-2 copies/16S r RNA copies.