Abstract:The transmission of antibiotic resistance genes (ARGs) is a potential threat to human health.ARGs are present as both intracellular and extracellular fractions of DNA in the environment.Intracellular ARGs (iARGs) and extracellular ARGs (eARGs) have different distribution and transmission characteristics in different environments.In this paper,we first categorized chromosomal,plasmid-borne,phage-associated ARGs into iARGs and eARGs with regarding to their occurrence states,and then summarized the methods for the isolation and detection of iARGs and eARGs from soil,water,and the atmosphere.Afterwards,we described the abundance distribution of iARGs and eARGs in livestock and aquaculture farmlands,wastewater treatment plants,rivers,oceans,and the atmosphere and compared their transmission methods and ability.This paper is expected to provide a theoretical reference for the control and assessment of the health risks of ARGs in the future.