When scientists exposed mice to friendly soil bacteria called Mycobacterium vaccae, it was found that the rodents perform a behavioral task commonly used to test the effectiveness of antidepressant drugs.
Mycobacterium, which has already been successfully used in people as a vaccine against tuberculosis and in asthma sufferers, also boosted the production of serotonin, a mood-regulating brain chemical.
Neuroscientist Christopher Lowry at the University of Bristol in England said, "These studies help us understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health. They also leave us wondering if we shouldn't all spend more time playing in the dirt."
According to Live Science, experts believe that the microbes are affecting the brain indirectly by causing immune cells to release chemicals called cytokines.
Cytokines are chemicals known to activate sensory nerves that stimulate the brain. The findings are published in the journal Neuroscience.
