Why do we sleep? For decades, scientists believed the answer was found only in the brain. But new research from Washington State University suggests microbes may also play a role. The team discovered that bacterial cell wall molecules called peptidoglycans are naturally present in the brain and change with sleep cycles.
This finding supports what researchers call the “holobiont condition” — the idea that sleep is not just a brain-driven process, but one shaped by communication between our nervous system and the microbes living inside us. Instead of a top-down system, sleep may emerge from microbial signals that influence brain activity. Scientists even propose microbes may have helped shape the evolution of sleep itself.
The implications are big. If sleep is partly governed by microbial activity, future treatments for insomnia and other sleep disorders could target gut-brain communication, not just the brain alone. With growing evidence that microbes affect mood, appetite, and cognition, this research may change how we think about human biology — and the very origins of sleep.
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