Summary The purpose of this proposal is to provide equipment support to our currently funded NIGMS research project (2R35GM118159-08). Despite the possibility that the gut microbiome may represent a critical and readily modifiable component of human biology, the contribution of the gut microbiota to health, disease risk, and response to therapy remains largely undefined. The overall goal of the parent grant is to understand the principles, mechanisms, and processes that shape the interaction between gut microbial communities and their hosts. Our strategy is to combine anaerobic microbial genetics and high-throughput mass spectrometry with gnotobiotic (germfree and ex-germfree) mouse models to dissect these interactions. The central analytical approach in these studies is mass spectrometry, which we use to precisely measure microbial metabolism of dietary and other compounds and identify metabolites produced as a result of these activities. Although we have made significant progress in the project, the main limiting factor is the restricted access to time on a mass spectrometer. For this reason, we request funds to partially support the purchase of a mass spectrometer to support this project. The purchase cost, site preparation, installation, and maintenance of this instrument will also be significantly supported by the university.