Taxonomic and functional patterns across soil microbial communities of global biomes

Soil microbial communities have been shown to vary across many spatial scales, yet while variability exists between samples closely located in the same soil, variation between soils of different ecosystems is larger, creating biogeographic trends. Herein, thirty publically-available metagenomes from 11 globally distributed ecosystems were selected. These metagenomes were clustered by biome (i.e. forest, grasslands, tundra, semiarid and desert) based on morphoclimatic features. Protein biosynthesis, central carbohydrate metabolism, and antibiotic resistance were the most statistically different SEED subsystems among biome groups. CAZy-based annotation revealed that genes related to biomass degradation, sucrose and starch metabolism, and cell wall biosynthesis were overrepresented in forest and grasslands soils. As expected, desiccation and other stress resistance genes were prevalent in desert and semiarid soils. Antibiotic Resistance Genes (ARGs) were more abundant in forest and grassland soils, and multidrug efflux pumps were the most abundant ARG class. Heat Shock Proteins (HSPs) were generally more abundant in tundra, semiarid and desert. However, HSP60 and HSP20, predominantly from Archaea, were enriched in the Saline Desert soils. These results suggest that while a core microbiome and functional potential exist in all studied soils, local environmental conditions select for enrichment of specific functions important for survival in a given ecosystem. (C) 2017 Elsevier B.V. All rights reserved. (AU)