You are expelling a million microbes an hour, and they could be used to identify you

Your microbes are destroying the experiment.
Your microbes are destroying the experiment.
Image: Flickr/Robert Couse-Baker CC-BY
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You are not one organism, but a system of trillions. Each groove in the body and all its surfaces are teeming with microbes.

So it should be no surprise that anything you touch doesn’t just have your unique fingerprint but also your unique set of microbes. But the question that irked James Meadow at the University of Oregon and several of his colleagues was: did you also expel a unique microbial cloud in the air if we left out all the things you touch?

The answer according to their research, recently published in PeerJ, is yes. And the potential application in the field of forensics is fascinating, because while criminals might be able to avoid leaving behind their hair or their fingerprints, they will find it quite hard to stop any microbes on their bodies from leaking into a crime scene.

For their study, Meadow and his team put each participant in sterilized clothes in a sterilized room with filtered air and provided them with a sterilized laptop. The subject sat there watching YouTube videos or communicating with researchers via the laptop for six hours (with a break after four hours).

All the while, the researchers collected particles that flowed through the room and genetically sequenced those that were microbes. To be sure, they monitored a similar room with no person inside, as a control.

They found that each participant was expelling as many as a million microbes every hour. What was surprising was that they could tell the participants apart based on the microbes expelled, which mostly consisted of Streptococcus (found in the mouth), Propionibacterium and Corynebacterium (found on the skin), and for female participants even some common vaginal bacteria.

The total sample size of the study was only 11, so the results will have to repeated on a larger scale to be sure that the phenomenon wasn’t a fluke. But, from all we’ve been learning about microbes in the human body, the finding isn’t a shock.

It will take a lot of work for this to yield reliable forensic tools. Right now, it is not clear how easy it would be find someone’s microbial cloud in a non-sanitized environment. Also, we don’t know how often a person’s microbial cloud changes.

All of this may sound like a nightmare for germaphobes, but there is no need to worry. Humans and surely all other animals have been expelling these microbial clouds this whole time—it’s just more recent that we have the means to identify them.