Dementia with Lewy bodies (DLB), one of the most common forms of dementia, has no cure. Previous studies suggested that gut bacteria, the microorganisms that live in the human digestive tract, play a role in Parkinson’s disease, another neurodegenerative disorder, but the bacteria involved in DLB had not been identified. Now, a group led by researchers at the Nagoya University Graduate School of Medicine in Japan has identified three bacteria involved in DLB—Collinsella, Ruminococcus, and Bifidobacterium. Their findings, reported in npj Parkinson’s Disease, suggest new avenues for diagnosis and treatment.