PNNL

Abstract

Bio?lms are ubiquitous throughout aquatic environments and they are thought to promote the acquisition and dissemination of antibiotic resistant genes (ARGs). This study focused on the occurrence and distribution of ?ve types of ARG in naturally-occurring bio?lms, in comparison to associated sediment and water samples, from the Yangtze Estuary, which borders the meta-city of Shanghai, China. The detection frequency and abundances of most ARGs showed the following order: bio?lm > sediment > water, which can be attributed to a high level of antibiotics and metals that can accelerate the generation and propagation of ARGs in bio?lms. Most of ARG abundances were contributed by extracellular DNA (eDNA) in bio?lm and sediment samples. ARGs (sul1, sul2, tetAandtetW) in eDNA were signi?cantly correlated with TOC in both bio?lm and sediment samples. Furthermore, both intracellular DNA-associated ARGs per gram of microbial biomass carbon (MBC) and eDNA-associated ARGs per gram of non-MBC and were higher in bio?lms than sediments, and the partitioning coef?cients of ARGs in eDNA between bio?lm and water were higher than those between sediment and water. Our results provide new insight for evaluating the occurrence and abundance of ARGs in aquatic environments, con?rming that bio?lms are a signi?cant sink for ARGs in the estuarine environment.