Cross-Biome Comparisons of Soil Microbial Communities and Their Functional Potentials Via Shotgun Metagenomic Analyses.

We applied shotgun metagenomic analyses to 16 soils collected from a wide range of biomes, including multiple samples from polar deserts and hot deserts, as well as representative soils from boreal forest, arctic tundra,  tropical forest, and temperate forests/grasslands. All samples were compared at an equivalent sequencing depth (4 million quality reads per sample) with reads assigned to functional categories using MG-RAST tools. Overall, soils collected from arid environments shared metagenomes that were similar in composition. The desert metagenomes were distinct from those found in the more temperate soils and largely overlapping in composition suggesting that desert soil conditions (e.g. high pH, low moisture availability, and low levels of organic C inputs) shape metagenomes in a similar manner regardless of latitude. The desert soils also exhibited lower levels of functional diversity than the more temperate soils, a pattern that was mirrored in the taxonomic and phylogenetic diversity of the bacterial communities. We used both PCR-based 16S rRNA gene sequence data and the shotgun metagenomic data to characterize the bacterial communities in each of the soils and the taxonomic composition and structure of the communities was similar regardless of the method employed. Overall, we found that we could predict functional gene profiles across these 16 soils reasonably well from the bacterial community information, suggesting that the taxonomic and functional attributes of soil bacterial communities are strongly correlated across the wide range of biomes sampled here.