The Secret's in the Dirt

By Edward Tenner

It's not exactly what Ben Hogan had in mind with the phrase, but the Washington Post reports the latest evidence of the power of good bacteria:

Now scientists are beginning to think there could be medical and educational reasons for parents and teachers to encourage kids to play in dirt.

That's what Dorothy M. Matthews and Susan M. Jenks, biology professors at Sage College in Troy, New York, think they discovered in testing mice who ate Mycobacterium vaccae, a harmless bacteria or germ found in dirt almost everywhere.

The professors made little sandwiches of white bread, with a little smear of the bacteria, topped with peanut butter.

"Mice love peanut butter," said Matthews. "It was their reward when they ran through our tests."

The professors gave one group of mice M. vaccae (pronounced "emm vah-kay") sandwiches and another group just little peanut butter sandwiches, then watched how quickly the animals could work their way through a difficult maze to the peanut butter reward at the end.

"The mice fed M. vaccae navigated the maze twice as fast and showed far less anxiety than the other mice," Matthews said. "We did a second test, and removed M. vaccae from the first group's diet, and they still maintained their learning edge. And testing three weeks later -- which for mice is about the same as 2 1/2 years for humans -- showed that mice exposed once to M. vaccae could remember what they learned for a long time."

Don't try this at home? Actually we have been experimenting with ourselves and our children ever since the discovery of bacterial disease in the late nineteenth century. More recently, though, science has revealed the critical role of bacteria in the human body. As Discover noted a few years ago:

Today we know that trillions of bacteria carpet not only our intestines but also our skin and much of our respiratory and urinary tracts. The vast majority of them seem to be innocuous, if not beneficial. And bacteria are everywhere, in abundance--they outnumber other cells in the human body by 10 to one. David Relman and his team at Stanford University and the VA Medical Center in Palo Alto, California, recently found the genetic fingerprints of several hundred new bacterial species in the mouths, stomachs, and intestines of healthy volunteers.

"What I hope," Relman says, "is that by starting with specimens from healthy people, the assumption would be that these microbes have probably been with us for some time relative to our stay on this planet and may, in fact, be important to our health."

The Hygiene Hypothesis -- the idea that cleaner living paradoxically reprograms the immune system to allergic reactions -- has been gaining scientific support. The question is whether and when to shift major scientific research funds to a frontier study like the human microbial ecosystem. I think the slowdown in the rate of approval of new pharmaceuticals is telling us something -- not that regulators are too conservative but that it is getting harder to repeat past triumphs with past methods, even augmented by genomics and other new techniques. It's time to rethink research directions.

This article available online at:

http://www.theatlantic.com/technology/archive/2010/08/the-secrets-in-the-dirt/61673/