We all carry around a personalized "cloud" of microbes so unique to each of us that it could possibly be used like a fingerprint to identify us.
Scientists have long known that humans harbor a mostly beneficial population of microbes on the skin and in the gastrointestinal tract — a microbial colony known as the microbiome.
Some of that microbiome is emitted by people as a sort of haze or cloud that goes wherever they go, researchers at the University of Oregon report in the journal Peer J.
In their experiments, the researchers found that they could identify individuals from air samples taken in a sealed chamber after the person had left — just from the makeup of their personal bacterial "cloud."
"We expected that we would be able to detect the human microbiome in the air around a person, but we were surprised to find that we could identify most of the occupants just by sampling their microbial cloud," said study author James F. Meadow of the university's Biology and the Built Environment Center.
The researchers found that they could identify the experiment's 11 participating individuals in the sanitized chamber within four hours from the unique combination of bacteria each person left behind.
The researchers performed genetic sequencing on thousands of kinds of bacteria in 312 samples of air and dust gathered from the chamber to identify the types of bacteria present.
Several groups of bacteria the researchers identified are common to humans – including Streptococcus, commonly found in the mouth, and Propionibacterium and Corynebacterium, present on the skin – but the different combinations and percentages in samples were key to identifying the individuals.
"Our results confirm that an occupied space is microbially distinct from an unoccupied one, and demonstrate for the first time that individuals release their own personalized microbial cloud," the study authors reported.
Although the findings suggest a possible forensic use in identifying people such as crime suspects, the researchers caution that further research and refinement of the technique will be needed since the patterns they discovered "are likely to be more nuanced in a crowd of occupants, in a larger indoor space or in the presence of resuspended dust."
Still, they pointed out, the finding may further our understanding of how infectious diseases can be spread in indoor environments.
