Lactobacillus reuteri—an old acquaintance takes on a new task in colorectal tumor surveillance.

In this issue of Cancer Cell , Bell et al. identify the commensal bacterium Lactobacillus reuteri and its major metabolite reuterin as an important gatekeeper and promising target in colorectal cancerogenesis. They decipher a metabolic interplay in which L. reuteri is suppressed by metabolites from dysplastic intestinal epithelial cells which in turn are highly sensitive to the oxidative effects of the electrophile reuterin. [ABSTRACT FROM AUTHOR]