Substrate quality and availability are the utmost important factors controlling the carbon cycling in cryoturbated permafrost soils and thus defining their response to global warming. Since metabolites are the end-products of gene expression, their levels can be regarded as the ultimate response of a biological system to environmental conditions.
Here, we attempted to apply metabolomics (a set of analytical and biostatistics methods) to examine links between in vivo biological activity and environmental parameters in different horizons of permafrost soils. We compared metabolic profiles of different horizons of cryoturbated soils from Taymyr peninsula, northern Siberia. Our soil metabolome database included 72 samples (observations) and 109 metabolites (variables). The analysis of the database clearly discriminated three groups of samples and defined the metabolites contributing most to the differences between genetically similar horizons. The relative abundances of low molecular compounds were highest in organic and mineral top soils and strongly decreased with soil depth, reflecting the impact of root exudates and microbes in organic topsoils. Microbial phospholipid fatty acids (PLFA) in the frozen horizon (mainly, short-chain PLFA) indicated presence of living microorganisms. Surprisingly, higher abundance of most discriminating metabolites was observed in permanently frozen material as compared to the non-frozen layer above.
Our data indicates preservation of the metabolites in the permanently frozen part of the soil and confirms the katabolic activity (presumably, fermentation) in soils with permanent below zero temperatures. We suggest that metabolomics approach is a useful tool in helping to decipher microbial processes in soil.