Two-carbon folate cycle of commensal Lactobacillus reuteri 6475 gives rise to immunomodulatory ethionine, a source for histone ethylation

What is it about?

We have discovered a novel form of folic acid (Vitamin B9) that is made by probiotic bacteria that live in humans. The bacteria utilize this novel vitamin B9 version to produce an unusual amino acid, ethionine, which can serve as a building block for proteins. When activated human immune cells are exposed to ethionine, they calm down, their normal immune response is suppressed. Our data provides the molecular basis for this immunosuppressive behavior, which adds to the understanding on how gut bacteria interact with the human immune system. Our findings contribute to a better understanding of the human gut flora and suggest potential future applications for the prevention or treatment of gut inflammation and cancer.

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