Who knew that the one time you checked Facebook to stalk on your ex at your friend’s house had you leaving a telltale bacterial trail behind you?
Although it may sound far-fetched, the bacterial DNA that resides on human skin may someday be used for legal evidence in the courtroom. In a paper published online on March 15, Noah Fierer and his team at the University of Colorado, Boulder, revealed that the microbes on people’s fingers and hands leave a trail distinctive enough to identify who touched a particular object.
“Theoretically, as long as the DNA sequencing is very comprehensive, we could identify a person from their unique bacterial fingerprint with absolute certainty,” says Martin Blaser, a microbiologist at New York University who was not involved in the study.
Previous studies have found that our fingers and hands harbor an enormous diversity of bacteria — about 100 kinds of microbes typically grow on human skin. In addition, bacterial communities stay constant over time. For example, soap and hand sanitizers kill many bacteria on the palm and fingers, but the remaining microbes can restore the original composition of bacteria within hours.
In the current study, Fierer’s team proposed that it may be possible to take advantage of microbial diversity on human skin to identify a person. He and his colleagues swabbed keys from three computer keyboards, extracting as much bacterial DNA as possible. After matching the microbe communities on the keys to those on the fingertips of the computer owners, they were able to determine the owner of each keyboard.
Fierer also tried swabbing a computer mouse and comparing the bacteria on the mouse with a database of microbial fingerprints from more than 250 hands, including the hand of the mouse owner. He obtained, on average, 1,400 bacterial gene sequences per sample and was able to match the microbial fingerprint on the mouse to its proper owner. The team also successfully analyzed bacterial DNA two weeks after it had been left on a surface. The findings appear in the early online edition of Proceedings of the National Academy of Sciences.
To read Noah Fierer and his team’s work, visit the March 15 edition of Proceedings of the National Academy of Sciences at http://www.pnas.org/content/early/2010/03/01/1000162107.abstract
Although bacterial fingerprinting is an enticing option, human DNA forensics and fingerprint identification are way ahead of the game, Blaser says. The United States government already maintains large human DNA and fingerprint databases as well as technology to sequence and categorize data for easy retrieval, all of which would need to be developed for microbes.
“Fierer’s work is still preliminary, but the techniques are solid and show promise,” Blaser says. “With more time, bacterial fingerprinting may make its way into the courtroom.” Until then, the jury is out.
