Amir Mani Amir Mani Cory Henn Cory Henn Claire Couch Claire Couch Sonal Patel Sonal Patel Thora Lieke Thora Lieke Justin T. H. Chan Justin T. H. Chan Tomas Korytar Tomas Korytar Irene Salinas Irene Salinas American Association for the Advancement of Science 2024 Ectotherms have peculiar relationships with microorganisms. For instance, bacteria are recovered from the blood and internal organs of healthy teleosts. However, the presence of microbial communities in the healthy teleost brain has not been proposed. Here, we report a living bacterial community in the brain of healthy salmonids with bacterial loads comparable to those of the spleen and 1000-fold lower than in the gut. Brain bacterial communities share >50% of their diversity with gut and blood bacterial communities. Using culturomics, we obtained 54 bacterial isolates from the brains of healthy trout. Comparative genomics suggests that brain bacteria may have adaptations for niche colonization and polyamine biosynthesis. In a natural system, Chinook salmon brain microbiomes shift from juveniles to reproductively mature adults. Our study redefines the physiological relationships between the brain and bacteria in teleosts. This symbiosis may endow salmonids with a direct mechanism to sense and respond to environmental microbes. PDFDocument eng 2024-12-04T08:51:39.043529Z 2024 Animals Brain Microbiology Homeostasis Microbiota Salmonidae Microbiology RNA Ribosomal 16S Genetics Phylogeny Bacteria Classification Genetics Isolation & Purification 10934409 b application/pdf http://creativecommons.org/licenses/by-nc/4.0/