Coastal mudflats as reservoirs of extracellular antibiotic resistance genes: Studies in Eastern China

Despite coastal mudflats serving as essential ecological zones interconnecting terres-trial/freshwater and marine systems, little is known about the profiles of antibiotic resis-tance genes (ARGs) in this area. In this study, characteristics of typical ARGs, involving both intracellular (iARGs) and extracellular ARGs (eARGs) at different physical states, were ex-plored in over 1000 km of coastal mudflats in Eastern China. Results indicated the presence of iARGs and eARGs at states of both freely present or attached by particles. The abundance of eARGs was significantly higher than that of iARGs (87.3% vs 12.7%), and their dominance was more significant than those in other habitats (52.7%-76.3%). ARG abundance, espe-cially for eARGs, showed an increasing trend ( p < 0.05) from southern (Nantong) to northern (Lianyungang) coastal mudflats. Higher salinity facilitated the transformation from iARGs to eARGs, and smaller soil particle size was conducive to the persistence of eARGs in northern coastal mudflats. This study addresses the neglected function of coastal mudflats as eARGs reservoirs. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.