Microbe–Host Messaging

The bacteria inside human guts are more than mere passengers. They're believed to influence a variety of aspects of human health including metabolism, immunity, and maybe even mental health. But how could bacteria in the stomach possibly exert effects in distantly located body tissues like the brain? While the bacteria themselves don't penetrate the wall of the gut, some researchers think the bugs communicate with body’s tissues and organs via small membrane-bound vesicles. These tiny capsules, released from the bacteria, contain cell components such as proteins and metabolites and have been suggested to travel through the host’s blood stream. Evidence supporting this theory has been garnered from work in mice whose cells were programmed to glow red if they received specific signals from genetically engineered gut bacteria. Sure enough cells all around the animals’ bodies were found to light up, including neurons in their brains (pictured).

Written by Ruth Williams

Ruth Williams

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Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

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• Image from work by Miriam Bittel and Patrick Reichert, and colleagues
• Institute of Neurology (Edinger Institute), Goethe University, Frankfurt am Main, Germany
• Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in Journal of Extracellular Vesicles, October 2021