A paper in Proceedings of the NAS showed that scientists were able to successfully predict who owned which keyboard and mouse based on the bacteria left behind on the keys. Each of us carries a wealth of micro-organisms (you've got 100 times more non-human cells in your body than human cells!) and that microbial nation is distinctive — maybe as distinctive as a fingerprint. Wired talked to a microbiologist who wasn't impressed with the technique for criminal forensics (we don't know yet if microbial nations are static or if they change over time, nor how unique each one truly is), but they do note that microbes are useful in forensically distinguishing between identical twins.

"The results demonstrate that bacterial DNA can be recovered from relatively small surfaces, that the composition of the keyboard-associated communities are distinct across the three keyboards, and that individuals leave unique bacterial 'fingerprints' on their keyboards," wrote Knight and his colleagues at the University of Colorado, Boulder in a new paper in the Proceedings of the National Academy of Sciences… "If humans are thought of as a composite of microbial and human cells, the human genetic landscape as an aggregate of the genes in the human genome and the microbiome, and human metabolic features as a blend of human and microbial traits, then the picture that emerges is one of a human 'supra-organism'," argued a 2007 Nature paper lead-authored by Peter Turnbaugh, a Harvard microbiologist.

You're Leaving a Bacterial Fingerprint on Your Keyboard

Forensic identification using skin bacterial communities

(Image: Toshiba M30 keyboard cleaning -IMGP7931, a Creative Commons Attribution image from footloosiety's photostream)