The Future of Sterolbiome Research 

Professor Ridlon's pioneering discovery of the genes encoding bacterial steroid desmolase provides a mechanism by which host-associated microbiomes generate androgen sex hormones. The genes, known as desABCE, were found in both the gastrointestinal tract microbial communities, and also bacteria inhabiting the urinary tract. The enrichment of these genes in the urinary tract of some men may represent a life-long risk factor for prostate cancer, which is driven by androgens. Professor Ridlon assembled a multi-disciplinary team to measure desAB genes in the urine of healthy control men, and men newly diagnosed with prostate cancer. He has been developing a research focus known as the host "sterolbiome," the collection of microbiome genes involved in steroid metabolism. His work resulted in characterization of many novel enzymes.  

During his CAS release-time appointment, Professor Ridlon will utilize several approaches to map out the urinary sterolbiome. This work has significant implications for medical diagnostics which rely on accurate measurements of urinary steroids. If bacteria modify host steroids in the urine, patients may not receive the correct diagnosis. The production of androgens also has implications for the results of doping tests performed on professional athletes. Furthermore, epithelial cells that line the colon express androgen receptor, as do immune cells that infiltrate and survey the intestinal barrier. The gut is thus expected to be highly responsive to androgens, and this may represent a form of host­ microbe communication that has yet to be explored.