02/05/2026
The soil bacterium that mirrors the effects of antidepressant drugs like Prozac is Mycobacterium vaccae (M.vaccae). This harmless, non-pathogenic microbe is found in healthy organic soil and has been shown to stimulate the same parts of the brain that produce serotonin, the “happy” chemical, without the side effects associated with pharmaceutical drugs.
🗂️How Mycobacterium vaccae Works. M.vaccae interacts with the human body and brain through several biological pathways:
📑Stimulating Serotonin Release: When humans are exposed to the bacterium—through inhalation, ingestion, or topical contact—it activates a specific group of neurons in the brain that produce serotonin. Specifically, it has been found to activate serotonergic neurons in the interfascicular part of the dorsal raphe nucleus (DRI).
📑Anti-inflammatory Response: The bacterium has long-lasting anti-inflammatory effects on the brain. This is critical because neuroinflammation is a known risk factor for mental health disorders, including anxiety and depression. By dampening this inflammation, M.vaccae helps promote stress resilience.
📑Increasing Serotonin Biosynthesis: In studies, treatment with M.vaccae increased the expression of tph2, an enzyme involved in the biosynthesis of serotonin.
📑Affecting Brain Regions: Increased serotonin levels have been specifically noted in the medial prefrontal cortex, a region of the brain that modulates anxiety and regulates emotional behavior.
🗂️Method of Exposure and Effects. Humans typically encounter M.vaccae while gardening or spending time in nature. The bacterium can enter the body by:
📑Inhaling it from the air or soil dust.
📑Ingesting it through water sources or from picking and eating fresh produce like lettuce or carrots.
📑Topical absorption through skin contact or entry through small cuts.
Research on both mice and humans suggests that these effects can last for up to three weeks after exposure. Beyond mood elevation, studies have indicated that M.vaccae may improve cognitive function and learning abilities; for example, mice exposed to the bacteria were able to navigate mazes twice as fast as those without it.
