Unveiling soil microbial communities and resistomes in northern Alaska National Wildlife Refuges

Abstract

Microbial communities residing in pristine high-latitude soils play a critical role in ecosystem function, but also harbor potential threats such as acting as reservoirs of antimicrobial resistance (AMR) genes. Current knowledge about these microbial communities and the resistance genes they carry presents limits to the ability to predict how these ecosystems will respond to climate change. This knowledge gap is particularly concerning in light of the potential public health threat posed by antimicrobial resistance harbored within these communities as antibiotic-resistant human infections continue to increase. This study investigated the microbial communities and details the antimicrobial resistance gene reservoirs in previously unsurveyed soils of three northern Alaska National Wildlife Refuges representing three distinct high-latitude biomes. I used a combination of 16S rRNA gene sequencing and metagenomic sequencing to characterize microbial community diversity and composition, as well as the AMR gene resistome. Also, I analyzed soil chemical components to evaluate their potential role in shaping these communities. My findings reveal significant geographic structure in microbial communities likely driven by differences in soil properties and dispersal limitation. Additionally, I found variation in pH significantly explained differences in alpha diversity, with slightly acidic soils harboring the highest diversity. The pattern of resistome structure matched the pattern of community structure, with microbial communities within the same refuge showing less variation than communities between refuges. Additionally, the data revealed significantly fewer AMR genes in the Selawik National Wildlife Refuge than in the other refuges. I found that variation in pH and in phosphorus concentrations significantly explained variation in AMR gene abundance with higher pH and higher phosphorus resulting in more AMR genes detected. My analysis identified that over 60% of AMR genes encoded resistance to lastresort glycopeptide antibiotics. My findings reveal that soil chemistry, particularly pH, plays a key role in shaping both microbial communities and AMR gene reservoirs in these pristine high-latitude soils. This study's characterization provides a crucial foundation for understanding how climate change and human activities might impact these ecosystems. Understanding the presence and distribution of AMR genes within microbial communities of pristine soils is essential for conserving these ecosystems and mitigating public health risks, including those associated with the spread of antibiotic resistance genes, especially those encoding resistance to last-resort antibiotics.