Pollution Characteristics And Influencing Factors Of Extracellular And Intracellular Antibiotic Resistance Genes In The Sediments Of Haihe Estuary,China

Antibiotic resistance genes(ARGs)were one of the emerging contaminants,which have potential threat to human health.With the increasing ARG pollution,the high abundance of ARGs has been detected in terrestrial water and soil,especially in the urban,agricultural and animal husbandry intensive areas.Estuaries lie between terrestrial/freshwater and marine ecosystems,receive considerable pollutants input from land-based sources,and are considerably influenced by human activities.However,little attention has been paid to combined research on extracellular ARGs(e ARGs)and intracellular ARGs(i ARGs)in the estuarine environment.In this study,we profiled e ARGs and i ARGs in sediments from Haihe Estuary,China by adopting high-throughput quantitative PCR and investigated their relationship with mobile genetic elements(MGEs),the bacterial community and environmental factors.The results showed that the abundance of e ARGs ranged from 9.06×10~6 to1.32×10~8 copies/g and that of i ARGs ranged from 3.31×10~7 to 2.93×10~8 copies/g.The high diversity and abundance of e ARGs and i ARGs detected in estuarine sediments indicated that estuarine sediments were key hotspots of e ARGs and i ARGs and the high abundance of ARGs carried in the extracellular DNA cannot be ignored.The abundance of multidrug resistance genes was the highest in all estuarine e DNA and i DNA samples and high abundance of vancomycin and carbapenemase resistance genes was detected in estuarine sediments.These three ARGs will pose a potential health risk to human,which we should pay attention on.Salinity,total phosphorus,temperature,p H and other environmental factors altered the composition and structure of the bacterial community and the abundance of some human pathogens increased along the estuary.Co-occurrence network analysis showed significant correlation between ARGs and bacterial community.These bacterial communities correlated to ARGs were thought to be possible ARG hosts.Partial redundancy analysis showed that the bacterial community and MGEs appeared to be the major drivers of ARG variance in estuarine sediment.This study provides an overview of the pollution and diffusion of broad-spectrum e ARG and i ARG along the Haihe Estuary,which provides evidence for the control of ARGs pollution and draws attention to the need to control pollutants in estuary ecosystems.