Over the past several years at the Round Lab, Allison Weis, Ph.D., a Postdoctoral Research Fellow at the Huntsman Cancer Institute, conducted research that resulted in the discovery that Bacteroides uniformis prevents CRC tumorigenesis by enhancing anti-tumor immune responses and reduces tumor growth through Natural Killer cells. But the bacterial factor that activates Natural Killer (NK) cells was still unknown. In this study, we extracted the spleens of three Germ Free Wild Type mice and isolated naive NK cells by cell sorting. We incubated those NK cells with different types of bacteria and their cell free supernatant (CFS) and analyzed the Natural Killer cells using flow cytometry through nine various cell markers. Specifically, PD-1, a protein found on the surface of NK, T and B cells saw a notable increase. These data indicates that protein PD-1 is one of the factors on NK cells that react after B. uniformis-induced activation towards reducing CRC tumorigenesis in mouse models.