Mapping the microbial diversity and natural resistome of north Antarctica soils

Abstract

The rising of multiresistant bacterial pathogens is currently one of the most critical threats to global health, demanding a better understanding of the origin and spread of antibiotic resistance. In this regard, the resistome hosted by the microbiota from natural and remote environments remains poorly explored. Moreover, little is known about the availability of antimicrobial resistance genes (ARGs) from these environments to be disseminated through horizontal transfer, potentially mediating the rise of novel resistance factors among clinically relevant pathogens. In this context, the North Antarctica soils are attractive ecosystems to study due to the presence of a microbiota naturally adapted to thrive in harsh conditions, including potential factors to resist natural toxic substances. In this work, we evaluated the antibiotic resistance of bacteria isolated from soils collected in humanized and non-intervened areas of North Antarctica. We identified resistance to a wide array of antibiotics, with isolates harboring up to 10 simultaneous resistances, mainly native Pseudomonas. Genomic analysis revealed the presence of a wide array of genes encoding efflux pumps but the lack of genes explaining some of the resistance phenotypes, suggesting novel uncharacterized mechanisms. Also, using 16S rRNA amplicon and shotgun metagenome sequencing, we explored the microbial diversity in the sampled soils and evaluated the presence of ARGs and their host microbiota. High microbial diversity was found in all the sites, with Proteobacteria, Bacteroidota, Acidobacteriota, and Verrucomicrobiota being the most abundant Phyla, while Candidatus Udaeobacter, RB41, Polaromonas, and Ferruginibacter the most abundant genera. We identified hundreds of genes potentially conferring resistance to more than 15 drug classes, both by short reads analyses and ARG detection among assembled contigs and MAGs obtained combining short and long-read sequence data. Polaromonas, Pseudomonas, Streptomyces, Variovorax, Bhurkolderia, and Gemmatimonas were the main host taxa of the identified ARGs. Part of these ARGs was found inside predicted plasmids, including a putative OXA-like beta-lactamase from Polaromonas harboring the key conserved residues of this kind of enzyme and a conserved predicted protein structure. All this evidence indicates that microbial communities from North Antarctica soil have a highly diverse natural resistome, part of it located inside mobile genetic elements, which would act as a source of novel ARGs.