Research team discovers new kind of bacterial “fingerprint”

Forensic scientists may soon have a valuable new item in their tool kits—a way to identify individuals using unique, telltale types of hand bacteria left behind on objects such as keyboards and computer mice, according to a new CU-Boulder study.

The study showed that “personal” bacterial communities living on the fingers and palms of individual computer users that were deposited on keyboards and computer mice matched the bacterial DNA signatures of users much more closely than those of random people. While the development of the technique is continuing, it could provide a way for forensics experts to independently confirm the accuracy of DNA and fingerprint analyses, said CU-Boulder Assistant Professor Noah Fierer, chief author on the study.

“Each one of us leaves a unique trail of bugs behind as we travel through our daily lives,” said Fierer, an assistant professor in CU-Boulder’s ecology and evolutionary biology (EBIO) department. “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.”

Using powerful gene-sequencing techniques, the team swabbed bacterial DNA from individual keys on three personal computers and matched them up to bacteria on the fingertips of keyboard owners, comparing the results to swabs taken from other keyboards never touched by the subjects. The bacterial DNA from the keys matched much more closely to bacteria of keyboard owners than to bacterial samples taken from random fingertips and from other keyboards.

In the second test, the team swabbed nine computer mice that had not been touched in more than 12 hours and collected palm bacteria from the mouse owners. The team compared the similarity between the owner’s palm bacteria and the owner’s mouse with 270 randomly selected bacterial samples from palms that had never touched the mouse. In all nine cases, the bacterial community on each mouse was much more similar to the owner’s hand.

The study showed the new technique is about 70 to 90 percent accurate, a percentage that likely will rise as the technology becomes more sophisticated. “This project is one example of why I got into science,” said Fierer.

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