Microbial niche breadth as a tool to identify controls on carbon and nutrient cycling across environmental gradients

Soil microbes govern biogeochemical processes such as carbon and nutrient cycling, but the microbial controls on soil nutrient stoichiometry vary under different environmental contexts. Recent evidence suggests that microbial genomic traits such as GC content and genome size correlate with soil pH and soil C: N ratios, but how this pattern relates to the fate of soil organic carbon (SOC) and in which microbial groups this occurs is inconclusive. The rapid generation of environmental metagenomic datasets presents a unique and relatively untapped resource that can be used to examine microbial niche breadth, or soil resource use and reuse, and how specific groups of microbes respond to environmental gradients. Metagenome assembled genomes (MAGs) for soil microbes can describe the functional potential of populations, serving as valuable descriptors of niche breadth for soil microbial communities.  Here, we aimed to identify the ecological factors structuring microbiological nutrient cycling functions, and how they vary with microbial traits and functional groups by harmonizing soil metagenome datasets with soil nutrient measurements across space and time. We applied the Hutchinsonian niche hypervolume concept to examine relationships between microbial functional niche and environmental resource space. We expect that comparative analysis of MAGs across diverse environments varying in soil organic C and N can identify specific functional and/or taxonomic groups of microbes contributing to SOC dynamics, such as fungal saprotrophs. Biotic and abiotic controls such as climate and vegetation that influence these groups of microbes can then be identified using large-scale amplicon sequence datasets that represent broad spatiotemporal scales.