Project Summary & Abstract Bacteria communicate with their environment using a chemical language consisting of secreted small molecules, also referred to as natural products or secondary metabolites. Nowhere is this communication more relevant to human health than in the microbiome where hordes of beneficial microbes and pathogens `talk' and compete amidst a cacophony of small molecule exchanges. Corynebacteria are commensal residents of the skin and upper respiratory tract and have recently emerged as opportunistic, multidrug-resistant pathogens. However, virtually nothing is known about their secondary metabolomes and, thus, how they compete with other microbes and interact with host cells. In the current application, we propose to characterize the secondary metabolomes of three corynebacterial strains using high-throughput elicitor screening (HiTES), a state-of-the-art chemical biology and natural product discovery approach that identifies the small molecule products of silent or sparingly expressed biosynthetic genes. Specifically, we plan to uncover the secondary metabolites that the three Corynebacteria use to compete with one another in intra-genus chemical warfare, to antagonize Staphylococcus aureus in inter-genus competition, and to modulate cytokine production by host cells in inter-kingdom associations. Together, the results of this proposal will elucidate intra-genus, inter-genus and inter-kingdom interactions by important and underexplored bacteria in the body. The feasibility for the proposed exploratory grant is provided by recent application of the HiTES approach to streptococcal bacteria in the microbiome. The proposed studies can therefore be completed in the two-year period and thus shine light on the lifestyles of important microbiome members while at the same time contributing important knowledge that can be used to develop therapies against corynebacterial infections.