Mycobacterium vaccae is a nonpathogenic[1] species of the Mycobacteriaceae family of bacteria that lives naturally in soil.
Research areas being pursued with regard to killed Mycobacterium vaccae vaccine include immunotherapy for allergic asthma, cancer, depression,[4][5] leprosy,[6] psoriasis, dermatitis, eczema and tuberculosis.[6]
A research group at Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, England, UK has shown that Mycobacterium vaccae stimulated a newly discovered group of neurons, increased levels of serotonin and decreased levels of anxiety in mice.[1] Other researchers fed live Mycobacterium vaccae to mice, then measured their ability to navigate a maze compared to control mice not fed the bacteria. "Mice that were fed live M. vaccae navigated the maze twice as fast and with less demonstrated anxiety behaviors as control mice", according to Dorothy Matthews, who conducted the research with Susan Jenks at the Sage Colleges, Troy, New York, USA.[7]
https://en.wikipedia.org/wiki/Mycobacterium_vaccae