Project Summary The overarching goal of this supplement request for R35 GM128618 is to support Jasmine Walsh, a promising PhD candidate from an under-represented group, in her research training in the PI’s laboratory. Specifically, Jasmine is studying gut bacterial metabolism of endogenous steroid hormones. The Devlin lab has been studying gut bacterial conversion of glucocorticoids, metabolites that regulate immune function and metabolism, into progestins, metabolites that are neurosteroids and sex hormones. Jasmine will contribute to these efforts by identifying gut bacteria and bacterial enzymes that produce progesterone (P4), tetrahydroprogesterones (THPs), and 11β-hydroxy tetrahydroprogesterones (11β-OH THPs). She will also investigate the in vivo relevance of these findings by exploring whether gut bacteria produce these compounds in specific pathogen-free and gnotobiotic pregnant and non-pregnant female mice. Finally, she will characterize the effects of progestin metabolites on progesterone receptor (PR) signaling in vitro. This supplement will provide Jasmine with rigorous training in biochemistry, analytical chemistry, microbiology, cell culture, and mouse studies in the context of the microbiome field. In addition, the career development plan supported by this supplement will act as a springboard for Jasmine to progress to the next stage of her scientific career and will help her advance toward her ultimate goal, which is running her own laboratory. The proposed supplement will enhance the goals of the parent R35 while advancing the NIH mission for enhancing diversity.