Antarctic soil microbiomes encode structurally conserved and phylogenetically diverse beta-lactamases.

Antimicrobial resistance is a major global health threat shaped not only by clinical settings but also by environmental reservoirs, in line with the One Health framework. Antarctic and Subantarctic soils represent a largely unexplored component of the environmental resistome, particularly beta-lactamases, whose diversity, structural features, and biogeographic patterns remain poorly resolved. Here, we applied an integrative metagenomic approach combining sequence-, structure-, and function-based similarity to systematically identify putative beta-lactamase orthologs across an extensive collection of Antarctic and Subantarctic soil metagenomes. We detected multiple beta-lactamase classes and families, with a predominance of class A serine beta-lactamases and subclass B3 metallo-beta-lactamases. Several previously uncharacterized families and divergent variants were identified, many of which retain conserved catalytic architectures. Beta-lactamase diversity and relative abundance were strongly patterned across three major biogeographic clusters: Subantarctic islands, the Antarctic Peninsula and surrounding islands, and continental cold deserts, mirroring shifts in microbial community composition. The Antarctic Peninsula and maritime Antarctica exhibited the highest overall beta-lactamase abundance. Analysis of more than 3500 metagenome-assembled genomes indicated that most beta-lactamases were encoded by members of