| 英文摘要: | Over 100 gigatons of terrestrial plant matter are produced globally each year. Ninety percent of this biomass enters the pool of dead organic matter in soils. However, our understanding of how communities of decomposer microorganisms process this material is not yet clear enough to predict the rate of carbon and nutrient cycling through soils. This is a major gap in our knowledge of ecosystem stability, as the biochemical process of decomposition determines the balance between carbon storage on land and the amount of carbon dioxide released from the biosphere to the atmosphere. Decomposer microorganisms are a highly diverse group of organisms: hundreds of species of microbes can live on a piece of decomposing woody debris at any one time. The objective of this research is to identify the specific, biochemical ways in which these decomposer species interact during the decay of plant matter, and how these interactions shape the species composition and total activity of these important communities over time. The results of this research will provide detailed information on the biological processes that give rise to one of the largest natural fluxes of carbon dioxide to the atmosphere. The project will include training opportunities for a postdoctoral scholar, and graduate and undergraduate students. The PIs will disseminate a K-12 curriculum about the importance of decomposer microorganisms through summer programs for children.
Microbes are the engines of ecosystem-level biogeochemical cycling, such that their frequent synergistic and antagonistic interactions likely determine rates of these processes. A widely observed pattern of microbial species interactions occurs during decay of dead organic matter (i.e. litter), where communities of decomposer fungi succeed one another over time and track changes in the abundance of litter chemicals. Across systems, the same orders, genera, and species of fungi often dominate the decomposer community present at each stage of decay, yet the mechanisms by which these individual species consistently become dominant, and how they influence the biogeochemistry of the system, are unknown. The objective of this research is to identify the molecular-level factors that regulate these processes. While classic theories of species interactions originally developed for macroorganisms may apply to decomposers, new information on microbial metabolic strategies, such as cross-feeding between species and anticipatory regulation of growth and metabolism, may also account for the structure and activity of these communities. Changes in litter and microbial chemistry during decay constitute one of the most predictable sequences of stimuli for microorganisms in nature, yet it is not known how microbes respond to these stimuli, or how these processes vary across a diversity of fungi. The proposed research will address these questions by leveraging state-of-the-art transcriptomics, metabolomics, and metabolic flux modeling with a model fungal-litter system to 1) determine the molecular stimuli that mediates interactions between competitively dominant and rare fungal species, 2) develop metabolic network models that predict the outcomes of species interactions, community dynamics, and metabolite cycling through litter, and 3) test whether molecular-level models can successfully recapitulate community and biogeochemistry dynamics previously observed in natural litter decay. The potential contribution of this work will be a complete gene-to-ecosystem-level analysis of decomposer fungal interactions, expanding and building linkages between the fields of analytical chemistry, molecular biology, microbiology, community ecology, and ecosystem ecology. |