Above: Image © istockphoto.com/DawnPoland

Did you know? Many commonly used antibiotics, including penicillin and vancomycin, were originally discovered in soil.Have you noticed how springtime can bring smiles to faces that were frozen, scowling, and hidden behind scarves all winter? It could be the result of more daylight, warmer temperatures, and less shoveling. However, some scientists would argue that soil bacteria called Mycoplasma vaccae might also be partly responsible.

As you head outside to clean up the garden or enjoy a walk in the newly-thawed woods, you may be getting a dose of mood-boosting drugs courtesy of this microscopic friend. In fact, a series of scientific studies have shown that this dirt-living bug not only makes people happier, it may also may make them smarter!

Serotonin booster

M. vaccae is a bacteria with a long medical record, having been used to stimulate the immune system of both tuberculosis and cancer patients. Researchers also noticed that cancer patients deliberately exposed to M. vaccae experienced less pain, could think more clearly, and had higher energy levels than patients who were not. Curious about why this might be, another group of scientists injected mice with dead bacteria and watched what happened.

The mice were put through a series of tests, and those injected with the bacteria performed better on a stress test called the Forced Swim Test. The bacteria-injected (or test) mice swam for longer than those what did not receive injections (the control mice). In addition to performing better on the stress test, the test mice were also able to find their way through a maze more quickly than the control group.

Did you know? In Canada, 5% of male youth and 12% of female youth have experienced serious depression.Even if you’re not that interested in rodent swimming lessons, the test showed that M. vaccae produced exactly the same effect as treating mice with anti-depressant drugs. And when researchers studied the mice’s brains, they found that the test mice had higher levels of serotonin than the control group.

Serotonin is a naturally-occurring chemical that is part of group of molecules called neurotransmitters. It carries messages across the gaps (synapses) that separates nerve cells (neurons) in the brain. More specifically, serotonin carries messages within the limbic (emotional) system of the brain to create feelings of happiness and well-being. If your brain doesn’t have enough serotonin to send these signals, you can be more susceptible to mental disorders like depression, anxiety, and schizophrenia.

These conditions are often treated with Serotonin Selective Reuptake Inhibitors (SSRIs), which prevent serotonin from being absorbed by surrounding cells. This increases the amount of useable serotonin in the gaps between cells, keeping messages moving and moods stable.

Scientists believe that when M. vaccae enters the human body, it causes your immune system to boot up, setting off a cascade of events that ends with a rise in the amount of serotonin in your brain. M. vaccae also produce cytokines, which are a group of proteins released by cells in your immune system. When cytokine levels increase, serotonin levels go up as well.

Do live bacteria make a difference?

Another group of researchers wondered what would happen if mice were exposed to live bacteria instead of the heat-killed version used in the previous study. They spiked samples of peanut butter with M. vaccae and let the mice eat it. Just like in the first study, test mice were able to complete tasks more quickly and while showing less stress than the mice that hadn’t ingested the bugs.

Did you know? A long list of celebrities suffer from depression, including funny-guy Owen Wilson, pop singer Britney Spears and baseball star Ken Griffey Jr.Scientists also discovered that the improvement in brain power continued for about three weeks after the mice stopped eating peanut butter spiked with live bacteria, whereas the positive effects of the heat-killed bacteria on brain power only lasted about three days. If you consider that a mouse only lives for about two years, a three-week boost to their smarts is pretty impressive!

Don’t worry: no one is suggesting that you to eat bacteria-containing peanut butter to cheer you up and clear your head! You can enjoy the benefits of M. vaccae simply by taking some deep breaths of fresh air. There’s a chance bacteria suspended in the air will make their way into your lungs. Better yet, get your hands dirty. Small cuts or scratches in your skin provide another way for the bacteria to enter your system.

Even if you don’t have a serious mental health condition, you’ve likely experienced stress related to school commitments, social engagements, and all of the other demands on your time. And I’d guess that when assignments are due or it’s the night before a big exam you would be thrilled to think more clearly. Instead of energy drinks and all-nighters, for a boost to your mood and brain power you may want to consider closing the book, putting down the tablet, walking away from the computer and going outside to take in a little M. vaccae… and then get back to studying!

Learn more!

Ingestion of Mycobacterium vaccae decreases anxiety-related behavior and improves learning in mice (2013)
D. M. Matthews & S. M. Jenks, Behavioural Processes 96
Link to abstract. Subscription required to view full text.

Identification of an immune-responsive mesolimbocortical serotonergic system: Potential role in regulation of emotional behavior (2007)
C. A. Lowrya et al., Neuroscience 146

Scientific articles on the effect of M. vaccae on the serotonin system, mood, and behaviour.

Is Dirt the New Prozac? (2007)
Josie Glausiusz, Discover

News article on research into the antidepressant effects of M. vaccae.

Shawna Hiley

Shawna first fell in love with science when she won her grade 7 science fair with a project on Solutions, earned a trip to the regional fair and met lots of smart kids fired-up about all kinds of cool projects. The science bug stuck and she went on to complete a B.Sc. in Biochemistry and a Ph.D. in Molecular Genetics. She eventually shifted her focus from research to teaching, and more recently has branched out again with writing. She finds all kinds of science fascinating and loves to share that passion with anyone who will listen!



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