Most microbes produce small molecule secondary metabolites as signals and/or antibiotics that control interactions between species. Despite their immense medical importance, the natural diversity and function of these molecules remains obscure. This prevents a full understanding of how microbial communities maintain critical ecosystem functions such as healthy host-microbe relationships. To further understand these systems, this project will generate networks of microbial interactions and their associated secondary metabolites based on the co-occurrence of particular microbes and secondary metabolites in environmental samples. Work will be conducted on the fungus-growing ant Trachymyrmex septentrionalis as an experimental model for these studies, profiling host-microbe interactions that are mediated by secondary metabolites within ant colonies collected throughout the Eastern USA. The T. septentrionalis symbiosis will also be utilized to broadly demonstrate the basics of animal-microbe interactions via a public display that will be linked to newly designed web resources. In addition, postdoctoral, graduate, and undergraduate researchers will be trained in microbiology and chemical ecology, including members of underrepresented groups. This project will therefore broadly advance understanding of the diversity and natural function of secondary metabolites and their impacts of host-microbe interactions.
Nearly all microbes produce secondary metabolites. These molecules are particularly common in symbioses, where they mediate host-microbe interactions. Such interactions are typically studied using low-throughput approaches that remove secondary metabolite-producing organisms from their natural communities. These experiments are therefore insufficient to determine in situ secondary metabolite diversity, and cannot unambiguously link specific molecules to the ecological interactions that they naturally mediate. To overcome these limitations, this project will develop an approach to comprehensively identify interspecific interactions mediated by secondary metabolites by identifying patterns of co-variation between interacting taxa and the secondary metabolites that mediate these interactions, using the fungus-growing ant Trachymyrmex septentrionalis as an experimental model. In this approach, taxa that interact mutualistically will co-occur with both each other and the metabolite that mediates this mutualistic interaction. Reciprocally, taxa that interact antagonistically will rarely co-occur, and the metabolite that mediates this antagonistic interaction will co-occur with the producing taxon but not the target taxon. In situ interactions will be recapitulated using laboratory ant colonies microbial cultures. Researchers at various levels will be trained in these molecular and chemical ecology methods and museum and online resources to disseminate results to the broader public will be developed. Together, this project will provide a methodological approach to map interactions mediated by secondary metabolites in microbial communities and identify the in situ functions of such molecules.
