Using Metatranscriptomics to Understand Carbon Decomposition in Forest Soils
Decomposition of plant materials in soils is accomplished by a complex and highly diverse community of microorganisms. The vast majority of these microbes cannot be grown in laboratories, and the roles of different species in decomposition and responses to changing environmental conditions are not well understood. Ecologists have demonstrated that the addition of nitrogen to forest soils significantly slows the rate of carbon decomposition, but it is not well understood why this change occurs. Recent advances in soil metatranscriptomics, the direct analysis of microbial community gene expression in environmental samples, have provided researchers with a more sophisticated set of tools to track changes in microbial community structure and function. In a new study, a collaborative team of scientists at Los Alamos National Laboratory and the University of Michigan have completed a metatranscriptomic analysis of forest soils at a long-term ecological experiment examining impacts of nitrogen addition. By developing a new technique for metatranscriptomic sampling, the team was able to complete a much deeper analysis of community metabolic potential than has been previously attempted. Using this approach, fungal and bacterial genes involved in degradation of plant lignocellulose were determined to undergo large changes in expression at two separated sites with elevated nitrogen. Overall pattern shifts were consistent with decreased carbon decomposition rates, but specific mechanisms appeared to vary between the different forest sites. As climate change processes shift environmental variables and agricultural practices continue to alter nitrogen inputs in terrestrial soils, understanding their coupled impacts on microbial community activities will be crucial to more confidently modeling and predicting impacts on different ecosystems.
Hesse, C. N., R. C. Mueller, M. Vuyisich, L. Gallegos-Graves, C. D. Gleasner, D. R. Zak, and C. R. Kuske. 2015. “Forest Floor Community Metatranscriptomics Identify Fungal and Bacterial Response to N Deposition in Two Maple Forests,” Frontiers in Microbiology, DOI: 10.3389/fmicb.2015.00337.