S45: Soil microbial community responses to 10 years of warming as revealed by comparative metagenomics

Soil microbial communities are extremely complex, composed of thousands of low-abundance microbial species (<0.1% of total). How such complex communities respond to natural as well as anthropogenic fluctuations, including major perturbations such as global climate change, remains poorly understood, severely limiting our predictive ability of soil ecosystem functioning and resilience. In this study, we have compared six paired replicate whole-community shotgun metagenomic datasets from two adjacent grassland soils in Midwest USA; one that was undergoing infrared warming by 2°C for 10 years, which simulated the effects of climate change, and an adjacent soil that received no warming and thus, served as control. 10-15 Gb short read (100 X 100 bp) sequence data were obtained per dataset (~60 Gb per soil treatment), using the Illumina HiSeq-2000 platform. Our analyses revealed that the warmed communities showed small but highly significant shifts in composition and metabolism and these shifts were community-wide as opposed to being attributable to a few taxa. Key metabolic pathways related to carbon cycle, e.g., cellulose degradation (~13%) and CO₂ production (~10%), were significantly enriched under warming. These community shifts were interlinked, in part, with higher primary productivity of the aboveground plant communities favored by warming. Collectively, our results indicate that the microbial communities of the temperate grassland soils studied here show positive feedbacks to warming and advance understanding of the modes and tempo of soil microbial community adaptation to environmental perturbations. The bioinformatics challenges associated with the analysis of such complex and large datasets will be also discussed.