Human beings are literally covered with bacteria, both inside and out. It’s estimated that we have about 150 different species of bacteria on our hands alone. Interestingly, we each possess a unique personal flora. Only about 13% of the bacteria on my hands will also be on yours. Noah Fierer and his University of Colorado team used that information to see if they could identify the owner of certain objects from the bacteria on those objects.
By some estimates, the microbes in and on our bodies outnumber the cells containing our chromosomes by ten to one. Every time we touch something, we leave a trail of bacteria from our hands on the surface we touched. Fierer and his colleagues swabbed computer keyboards and computer mice, as well as the fingers and hands of volunteers who may or may not have touched those devices. Using a rapid DNA sequencing technique called ‘metagenomic survey’, the types of bacteria from the various samples were identified and compared.
The scientists had a 70-90% accuracy rate in matching the right keyboard or mouse to the right user. In addition, they found that the bacterial colonies on the tested objects remained virtually unchanged for up to two weeks.
Although this could one day be a promising addition to the forensic science arsenal, allowing detectives to identify who touched objects even without fingerprints, the accuracy would have to be drastically improved first. Fierer himself admits that his experiments were simply proof-of-concept tests.
As Fierer explains:
If the technique were perfected, it would be amazingly compelling. After all, not even identical twins share the same skin flora.