"Gut Microbes: from their "rump" to your muscle" from "Isotope Queen-Biogeochemistry Memoir" Must read. https://isotopequeen.blogspot.com/2020/04/gut-microbes-from-their-rump-to-your.html

My Stable Isotope Journey in Biogeochemistry, Geoecology, and Astrobiology Marilyn L. Fogel Geochemical Perspectives Letters http://www.geochemicalperspectives.org/online/v8n2