Germs in Your Gut Are Talking to Your Brain.

Germs in Your Gut Are Talking to Your Brain. Scientists Want to Know What They’re Saying.

Carl Zimmer

He and his colleagues gave antibiotics to mice prone to develop a version of Alzheimer’s disease, in order to kill off much of the gut bacteria in the mice. Later, when the scientists inspected the animals’ brains, they found far fewer of the protein clumps linked to dementia.
Just a little disruption of the microbiome was enough to produce this effect. Young mice given antibiotics for a week had fewer clumps in their brains when they grew old, too.

“I never imagined it would be such a striking result,” Dr. Sisodia said. “For someone with a background in molecular biology and neuroscience, this is like going into outer space.”

Following a string of similar experiments, he now suspects that just a few species in the gut — perhaps even one — influence the course of Alzheimer’s disease, perhaps by releasing chemical that alters how immune cells work in the brain.

He hasn’t found those microbes, let alone that chemical. But “there’s something’s in there,” he said. “And we have to figure out what it is.”

[Laird]

The article in the OP is now paywalled, and I haven't been able to read it, but this thread seems like a good place anyway in which to post this:

Scientists May Have Found Humanity’s Sixth Sense—In Our Gut

Darren Orf
Popular Mechanics
Jul 28, 2025

This new study, published yesterday in the journal Nature, describes the flagellin as the method through which neuropods, essentially neurons in your gut, regulate appetite.

According to the scientists, neuropods contain a receptor known as “toll-like receptor 5,” or TLR5, which then sends impulses to the brain via the vagus nerve—the gut-brain information highway that is also the longest nerve of the body’s autonomic nervous system. This shows how microbes living in our gut can communicate with the human brain.

To test the idea, scientists fasted mice overnight, and when supplied with a dose of flagellin to the colon, the mice ate less than expected. When the same experiment was conducted with mice that lacked the TLR5 receptor, the mice ate their fill and quickly gained weight. This suggests that this microbe-to-brain communication pathway plays a role in giving humans—and other mammals—the “I’m full” sense. This is what the researchers call our “neurobiotic sense,” and it very well could be our sixth sense. Or, maybe seventh? Or eighth? We’ve lost count.