In a study published Tuesday in PeerJ, researchers report that the unique signatures of bacteria a person left in the air can be used to identify them in just four hours of analysis.
The researchers placed subjects in sanitized chambers for 90 minutes, then tested the "cloud" of microbes they'd left behind in the air. Previous research has shown that humans change the microbial balance of their environments quite quickly. Your house will have a bacterial signature that fits your family and pets, but it will change as soon as you hire a dog sitter and leave for vacation. Meanwhile, your hotel room -- full of strange bacteria -- will adapt to your family's microbiome within hours.
So it's not surprising that the subjects each left behind some of the most common human-associated microbes. But the ratios were unique enough to identify most (though not all) of the individuals, hinting that these auras might be more like fingerprints.
The study is a small one -- just 11 subjects participated -- but it adds to a growing body of evidence that our multitudes of microbes are singular enough to serve as forensic evidence. Other researchers have argued that the exchange of bacteria between victim and perpetrator could be used as evidence in sexual assault cases. Another group is working with police in Hawaii, testing to see if bacterial signatures left on and around homicide victims could help tie suspects to the crime.
Actually using these microbial fingerprints in a courtroom is probably a long way off. But it's becoming clear that our tiny passengers interact with the world around us just as much as we do.
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