WASHINGTON (Reuters) – People leave more than fingerprints when they touch stuff — they also deposit a tell-tale trail of germs that could help investigators solve crimes, US researchers reported yesterday.

They were able to map a unique bacterial genetic signature left by nine different people, and said this germy DNA lasted though day-to-day temperature changes, humidity and sunlight.

“Each one of us leaves a unique trail of bugs behind as we travel through our daily lives,” Noah Fierer, a researcher at the University of Colorado at Boulder who led the study, said in a statement. “While this project is still in its preliminary stages, we think the technique could eventually become a valuable new item in the toolbox of forensic scientists,” he said.

Researchers have been learning that people are colonized with billions of microbes, both inside and on the body. And studies have shown that these colonies are unique to the individual and even to the place on the body.

Fierer’s team wanted to see how much of a trail might be left by these mostly benign bacteria. So they swabbed the computer keyboards of volunteers to show that indeed, each person left not only a trail of unique bacteria, but one that lasted.

In each case, they could show the DNA from the keyboards and computer mice more closely matched DNA from germs on the hands of the owners than they did anybody else’s hands.