A unique fog of germs follows us wherever we go, and it's so distinctive it may turn out to be better at identifying someone than the person's fingerprints, a study suggests.
These personal bacterial "clouds" are simultaneously so unique and so persistent they may even be a factor in future forensic investigation, researchers say.
In the journal Science, the researchers describe following seven families moving from one home to another, discovering that bacteria on your body will spread to colonize your new living spaces in a hurry.
"Everyone thinks hotels are icky," says Jack Gilbert at the Argonne National Laboratory, "but when one young couple we studied moved into a hotel, it was microbiologically identical to their home within 24 hours."
"No matter what you do to clean a hotel room," says Gilbert, one of the study authors, "your microbial signal has wiped out basically every trace of the previous resident within hours."
It happened even though the study participants swabbed and cleaned their hands, feet and noses and cleaned counters, floors and other surfaces of whatever home they were occupying, the researchers say.
Each participant's microbiome -- the combination of all of their microbial interactions -- was so unique it allowed the researchers to detect individual interactions among family members, determine what rooms each had been in, and even detect how long they spent in one part of the home versus another.
The forensic possibilities are obvious and almost endless, Gilbert says.
"We could go all J. Edgar Hoover on this and make a database of microbial fingerprints of people all over the world," Gilbert said, "and it's far more sophisticated than a standard fingerprint, which is just a presence or absence indication."
A person's microbiome could reveal who a person is, where they are or have been, what they've been eating and who else they might have interacted with.
The researchers say they've already worked with police in Hawaii, examining biomes left behind on dead bodies.
In the case of a homicide, for example, bacterial colonies might identify the last person with whom the victim was in contact, Gilbert says.
A fingerprint is rarely found on a body, Gilbert explains, but a microbial fingerprint certainly would be.
We acquire our own personal microbiome quickly, the researchers point out.
While babies when born are almost sterile, they quickly begin to pick up germs from their mothers, they said.
"You acquire your mother's microbiome and that kickstarts you into a progression that goes up to about the age of 2 years old," Gilbert says. "By the time you are 2, you have reached this stable unique fingerprint."