Metagenomic Analysis Reveals Northwest Pacific Ocean as a Reservoir and Evolutionary Hub of Antibiotic Resistance Genes

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/659680v1_ufig1.gif" ALT="Figure 1"> View larger version (81K): org.highwire.dtl.DTLVardef@139e191org.highwire.dtl.DTLVardef@10834c4org.highwire.dtl.DTLVardef@1c0544aorg.highwire.dtl.DTLVardef@1ddfd8a_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG Antibiotic resistance genes (ARGs) were identified as a novel type of environmental contaminants. Ocean is thought to be one of the ultimate environments where ARGs gathered. Marine ecosystems represent vast reservoirs of ARGs, yet their dynamics in open-ocean environments remain poorly characterized. Through large-scale metagenomic profiling of the Kuroshio Extension, a hydrographically dynamic region in the Northwest Pacific, we identified a striking enrichment of ARGs (1.81 x 10-3 ppm) at a frontal zone site (S30). The ARG abundance at this site exceeded coastal levels by 90-fold. Notably, multidrug resistance genes dominated this hotspot, with efflux pumps contributing 62% of the resistance mechanisms, a pattern distinct from the target-alteration strategies prevalent in other regions. The site exhibited unique microbial consortia, including pathogenic Acinetobacter (30.2% abundance) carrying clinically critical determinants (blaOXA-23, adeJ). Co-occurrence networks revealed horizontal transfer risks, linking pelagic Sphingobium to terrestrial-derived {beta}-lactamase variants. Crucially, we discovered three novel plasmid-borne resistance genes circulating in >15% of microbial populations, demonstrating open-ocean ARG diversification independent of direct anthropogenic inputs. These findings redefine oceanic frontiers as crucibles of resistance evolution, demanding urgent integration into global antimicrobial stewardship strategies.