Folks who “aren’t afraid to get their hands dirty” are admired in America.

They always seem to be robust, strapping people who know how to… as the saying goes… get ’er done.

Could it be they are getting a little help from microscopic friends who live in the soil?

Scientists suspect people who physically dig into dirt with their hands may be encountering “friendly” bacteria that stimulate positive brain responses.

British researchers had a hunch this type of interaction might be taking place when they noticed human cancer patients exposed to a type of bacteria during treatment unexpectedly began to cheer up.

They speculated that the bacteria affected brain cells that contain serotonin [sara-toe-nin], a powerful neurotransmitter believed to affect mood.

From this seed of an idea, the scientists examined the brains of mice that were given treatments that contained the bacteria, and found that it did indeed help sprout serotonin in the brain.

The researchers wrote in the journal Neuroscience that these beneficial bacteria, normally found in the soil, actually seem to affect behavior much like an antidepressant drug.

In that respect, the study sheds light on how the body and brain interact with the environment, and why a healthy immune system is important for maintaining mental health.

Future studies may determine whether bacteria in the environment can indeed directly affect our moods.

But in the meantime, don’t fret if you get a little dirt under your fingernails once in a while.

It may be good for you.