Eat Dirt!

Dust for breathing in.

Reported by CSIRO Australia ScienceMail, the soil bacteria Mycobacterium vaccae makes mice smarter and more relaxed, say researchers presenting at this week’s General Meeting of the American Society for Microbiology in San Diego.

Researchers Dorothy Matthews and Susan Jenks from the Sage Colleges in New York have found that M. vaccae increased the ability of mice to find their way through a maze.

Mycobacterium vaccae was first discovered on a cow udder in Austria in the 1970’s. It is widely distributed around the world and lives in soil.

In 2007 researchers from the University of Bristol found that M. vaccae stimulated certain neurons (nerve cells in the brain) and increased the levels of serotonin in the brain of mice who were treated with the bacteria. High levels of serotonin, which is a chemical that affects the signals in the brain, is linked to lower levels of anxiety and depression.

Dorothy Matthews decided to build on this research. ‘I wondered if [M. vaccae] had an effect upon learning because serotonin has multiple effects on the brain’, she said.

Unlike the 2007 study, which injected mice with M. vaccae that had been killed by a heat treatment, Dorothy and Susan fed mice live bacteria. They spread M. vaccae on small pieces of white bread along with lashings of peanut butter before feeding them to the mice.

Dorothy found that mice who were fed M. vaccae successfully navigated a complicated maze about twice as fast as mice who hadn’t eaten M. vaccae, and with less anxiety.

She then stopped feeding the mice M. vaccae but kept placing them in the maze a few times a week. She found that the mice who had eaten M. vaccae still performed better than the mice who did not, suggesting that the bacteria has a lasting affect on learning and memory.

Does this research mean that we should eat M. vaccae for breakfast to improve our memory? Perhaps not, says Dorothy, who thinks that the best way to get a dose of this bacteria is to breathe it in during a walk in the forest or by getting your hands dirty in the garden.


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