Syntrophy among microbial partners involves the exchange of metabolites, making processes possible that cannot be accomplished by either organism alone. These mutually beneficial relationships are now known to make essential contributions to the global carbon cycle. However, while syntrophic metabolism is found in nearly all anaerobic environments in nature, little is understood about the molecular, biochemical, or physiological basis of this important ecological process. The Syntrophomonas wolfei-Methanospirillum hungatei co-culture is the historical model for thermodynamically-limited syntrophic associations because both organisms are syntroph specialists that operate near the thermodynamic equilibrium, and that evolved by niche-associated interactions. This project will delineate the metabolic and regulatory systems involved in syntrophic metabolism in a well-defined model system. Syntrophic consortia are also excellent model systems to probe the mechanisms by which multispecies microbial communities interact because much about the metabolites used and the roles of each syntrophic partner is understood. Therefore, this project will serve as a paradigm for study of metabolism and gene expression in other multispecies microbial communities in key ecological habitats. The research will open up the next levels of study to decipher basic principles of this poorly understood biological process.
Broader Impacts This project will deepen understanding of the interesting phenomenon of syntrophy, of biological contributions to the global carbon cycle, and more broadly of the underlying molecular mechanisms at play in microbial communities. It will support training of graduate and undergraduate students in laboratory research involving anaerobic microbiology, microbial physiology, enzyme analysis, and analytical chemistry. The PIs will continue to be actively involved in developing undergraduate educational materials at their respective institutions. These include web-based materials that provide access for a wider audience. Existing programs are targeted for expansion to include institutions having significant underrepresented minority enrollments and students with disadvantaged backgrounds. In addition to educating, a goal is to promote interest in and enthusiasm for microbiology. Both PIs will also assist in judging local and/or national science fairs.
Syntrophic microbial partnerships are found in nearly all anaerobic ecosystems on Earth yet we understand very little about the molecular or biochemical basis of this important ecological process. Understanding how syntrophic consortia operate in anaerobic food chains at the metabolic and molecular levels is critical to understanding global carbon cycling and ecosystem function. The established S. wolfei-M. hungatei coculture was used to unravel the basic principles governing syntrophic partnerships. We hypothesized that special metabolic and sensory/regulatory systems are used by each syntrophic specialist to accomplish their syntrophic existence. Using a combination of high-throughput technologies including genome-wide expression profiling and proteomics we identified the metabolic network involved in syntrophic fatty acid catabolism. We determined the enzyme systems used for butyryl-CoA oxidation and which enzyme systems were used in electron bifurcation to drive this energetically difficult step. In the project we also dissected the metabolic pathways involved in the model methane producing partner. A major evaluation of the genome inventory and machinery used in methane formation was accomplished along with proteomic surveys to verify key predictions. We also constructed initial metabolic and regulatory models of both syntrophic partners to begin determining how each organism responds to the presence of its syntrophic partner. Together with the S. wolfei studies, these findings advance foundational knowledge needed to predict and explore related processes in other multispecies microbial communities. Our work will also serve as a paradigm to study other multispecies microbial communities.
