PROJECT SUMMARY/ABSTRACT: Ecologically-guided approaches have helped to reinvigorate natural products chemistry discovery efforts in recent years. Such approaches take advantage of ecological relationships in which chemical defenses produced by microbial symbionts benefit a host animal. These ecological relationships have recently been appreciated to be ubiquitous and sampling of these systems has an impressive track record of delivering novel, active compounds. However, generalized approaches for efficiently accessing novel chemical scaffolds and analogs of promising compounds have not been developed. As such, the potential for chemical discovery from such systems remains unrealized. The proposed project develops a host-associated biogeography framework for chemical discovery by tapping into a completely unexplored ecological niche with outstanding discovery potential: bacterial symbionts of Trachymyrmex ants in the American Southwest. In addition to uncovering novel antibiotic compounds, this work will quantify chemical diversity across this niche and determine geographic, environmental, and biological factors that predict the presence of active novel compounds. In Aim 1, a diverse library of 150 natural product extracts will be assembled from cultures of symbiotic bacteria isolated from southwestern Trachymyrmex ants. These ants will be systematically sampled from sites across the American Southwest such that the library captures diversity across multiple biogeography variables: location, host ant species, and habitat. Aim 2 will establish how these biogeography variables predict the distribution of antibiotic activity and chemical diversity across this library. Antibiotic activity screening against both ecologically-relevant and clinically-relevant microbial pathogens will establish correspondence between ecological and clinical activity. Metabolomics analysis of this library will reveal how molecules are distributed as a function of biogeography variables. Aim 3 of this proposal will deliver on ecologically-guided discovery from this unexplored niche by characterizing highly active novel compounds from this library, with a particular focus on synergistic antibiotics. Through activity-guided fractionation and detailed chemical characterization, this aim will yield 2-4 novel bioactive compounds. This proposal will lay the groundwork for further chemical discovery from this and other ecological niches. Undergraduate researchers will be engaged in all components of this work through modular summer and senior thesis research projects as well as a course-based research experience. The project will strengthen the research environment of multiple institutions at the Claremont Colleges through enhanced research opportunities on significant research, through a variety of new collaborations, as well as through bringing modern instrumentation to the Keck Science Department.