The composition of the gut microbiota changes as we age, which has been linked to healthy aging as well as susceptibility to disease. In a cohort of Japanese centenarians (aged 100 years and older), Honda and colleagues now show that compared to elderly and young individuals, centenarians are enriched in gut microbes capable of generating unique secondary bile acids, including iso-, 3-oxo-, allo-, 3-oxoallo- and isoallo-lithocholic acid (LCA). Through a culturing screen, they identify bacteria belonging to the Odoribacteraceae family, and describe the key enzymes and biosynthetic pathway that these bacteria encode for the production of isoalloLCA. They also demonstrate that this novel bile acid inhibits the growth of a range of Gram-positive gut pathogens in vitro, and protects mice against C. difficile expansion during infection. The authors suggest that it may be possible to exploit the unique bile acid-metabolizing capabilities of these bacterial strains to rationally manipulate the bile acid pool for health benefits.
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