WHEN YOU TOUCH a surface, you leave behind fingerprints—distinctive swirling patterns of oils that reveal your identity. You might also deposit traces of DNA, which can also be used to identify you. And you leave microbes. You are constantly bleeding microbes into your surroundings, and whenever you touch something, bacteria hop across from your skin.
It’s increasingly clear that everyone has a unique community of microbes—or microbiome—living on their bodies. We share species and strains but the exact roll call varies from person to person. “If you take a collection of people, their microbes will look very different but their genomes will look mostly the same,” says Curtis Huttenhower from the Harvard School of Public Health. So, could the DNA of these tiny variable residents also reveal our identity, just like fingerprints or our own DNA?