The strict anaerobic gut microbe Eubacterium hallii transforms the carcinogenic dietary heterocyclic amine 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP)

Summary 2‐Amino‐1‐methyl‐6‐phenylimidazo(4,5‐ b )pyridine ( PhIP ) is the most abundant food‐derived heterocyclic aromatic amine in well‐cooked meats and may contribute to the recognized carcinogenicity of processed meats. In this study, a panel of human gut microbes was tested for their ability to convert PhIP to a conjugate PhIP ‐M1. E ubacterium hallii was newly identified to catalyse the conversion of PhIP to PhIP ‐M1 with high efficiency. The reaction was shown to involve the metabolism of glycerol to 3‐hydroxypropionaldehyde as a key pathway. The proficiency of E . hallii in transforming PhIP in the presence of a complex intestinal microbiota was confirmed using batch fermentations inoculated with effluents from a continuous intestinal fermentation model mimicking human proximal and distal colon microbiota. In batch fermentations inoculated with proximal colon microbiota, PhIP ‐M1 transformation corresponded to an up to 300‐fold increase of E . hallii. In contrast, PhIP transformation of distal colon microbiota was low but increased by 120‐fold after supplementation with E . hallii . These findings indicate for the first time the relevance of the abundant commensal strict anaerobe E . hallii in the transformation of a dietary carcinogen that could contribute to its detoxification in the human colon.