Distribution and sources of antibiotic resistance genes in seamount sediments system

Antibiotic resistance genes (ARGs) are an emerging pollutant which have been detected in marine environments. Seamounts represent a prominent feature of the seafloor, exhibiting remarkable biodiversity and specificity. However, little is known for the existence of ARGs in seamounts, let alone the profiles of ARGs and their associations with microbial communities in seamount ecosystems. In this study, high-throughput sequencing and metagenomic approaches were employed to investigate the distribution, possible hosts, mobility, and potential sources of ARGs in sediments across various depths and slopes of the Zhongnan Seamount. Results showed that the most abundant ARG types were elfamycin, aminoglycoside, and tetracycline, accounting for 71.00% of the total ARG abundance. ARG abundance was significantly higher in abyssopelagic zone sediments, suggesting that the seamount acts as a sink and deep-sea regions may be a major reservoir for ARGs. A strong positive correlation between ARG abundance and mobile genetic elements (MGEs) indicated a high potential for horizontal gene transfer (HGT), with key genes EF-Tu, rpsJ, parC, and parE, identified as predominant mediators of horizontal transfer. Based on the analysis of metagenome-assembled genomes (MAGs), 36 bacterial genera were identified as ARG hosts, dominated by Methylomirabilota and Pseudomonadota. Fast expectation-maximization microbial source tracking (FEAST) model identified particles from the continental input which contributed 44.31% of ARG in seamount, indicating direct anthropogenic influences due to long-distance terrestrial pollutant dispersal from coastal area to deep sea. The origins of the other ARGs remain unidentified, suggesting the existence of abundant natural ARGs in the seamount. Overall, these findings indicate that a seamount is a hotspot for ARGs, provides valuable insights into the prevalence of ARGs in seamount environments and enhances our understanding of their sources, hosts and dissemination in seamount ecosystems.