Project Summary/Abstract Microbial communities inhabit nearly all environments on earth, including the human body, where they can influence health in myriad ways. These communities are often composed of hundreds or more species that form networks of metabolic interactions. Because metabolic interactions are complex and difficult to study at a molecular level, my research program focuses on interactions involving one family of metabolites – corrinoid cofactors – as a model to understand metabolic interactions among bacteria. Corrinoids are the vitamin B12 family of cobalt-containing metabolites that are used as enzyme cofactors for a variety of reactions. Corrinoids, like many amino acids, nucleobases, and other cofactors, are synthesized by only a fraction of bacteria that use them, and therefore are considered to be shared metabolites. Corrinoids are unique in their structural diversity, with over a dozen different forms discovered and up to eight of these forms found in microbial community samples, including the human gut. This structural diversity is a significant factor in microbial interactions because most bacteria are selective in the corrinoids they can use. The hypothesis driving this work is that structurally distinct corrinoids can be used as handles to manipulate microbial communities. Our previous NIGMS-funded research has laid the groundwork for the proposed research by establishing experimental methods; discovering and characterizing new genes; investigating corrinoid selectivity in enzymes, riboswitches, and bacteria; and creating a bioinformatic pipeline to predict corrinoid metabolism in bacteria. Our long-term vision is to build on this foundation to generate a newly detailed understanding of microbial community interactions through the study of corrinoids across scales, from molecular mechanisms to whole community perturbations. We will achieve this goal by (1) identifying genome sequence signatures predictive of bacterial corrinoid preferences in corrinoid- dependent enzymes and riboswitches, with an emphasis on evolutionary approaches and (2) investigating the molecular basis of corrinoid-dependent community dynamics by applying sequencing, culture-dependent, and genetic approaches to a model human gut-derived enrichment culture. As a test of our ability to understand and predict corrinoid-based metabolism and community dynamics, we will design and build bacterial strains with corrinoid-dependent metabolic networks, as well as consortia of bacteria with predictable dynamics. This research will be accomplished by using a combination of genetics, biochemistry, microbiology, and bioinformatics, building upon the past research of my group. Our work on corrinoids will not only serve as a model for microbial community interactions across systems, but may also lead to the development of new methods to alter microbial communities for beneficial outcomes.

Project Narrative A more complete understanding of the complex microbial communities that inhabit the human body is needed in order to develop new strategies to manipulate these communities for beneficial health outcomes. This research addresses this need by examining the vitamin B12 family of essential metabolites that are shared among bacteria and can influence microbial community structure.