The source and dissemination of ARGs in pristine environments: Elucidating the role of migratory birds in the Arctic.

Antibiotic resistance genes (ARGs) are a class of emerging contaminants that significantly threaten public health. In this work, the profiles of ARGs and microbial communities in the soil, sediment, migratory bird, and local deer fecal samples collected from the Arctic were characterized using a metagenomic approach. The results retrieved the baseline profiles of ARGs and identified the role of migratory birds in disseminating ARGs in the Arctic. A total of 26 ARG types and 718 subtypes were determined, and 131 core ARGs were identified. All the samples were dominated by multidrug resistance genes, and some genes resistant to antibiotics commonly used in anthropogenic were also detected. Characterization of ARGs in bird fecal samples was significantly distinct from other media, with higher abundance, richness, and unique ARGs detected. Proteobacteria was the most predominant phylum in soil and fecal samples, while Thaumarchaeota was prevalent in sediment samples. Firmicutes harbored the majority of ARGs in all samples. The results of FEAST indicated that migratory birds were crucial allochthonous ARG sources in the Arctic. These significant findings shed light on the global spread of ARGs and should facilitate efforts to map baseline levels of ARGs before the era of antibiotics.