Our Personal Microbial Cloud
Everywhere you go, in everything you do, you are surrounded by an aura of microbes. They drift down from your hair when you scratch your head, they fly off your hand when you wave to your friend, they spew out of your mouth when you talk. Even when you sit around doing nothing, you’re sitting in your own, personal microbial bubble. Made up of millions, billions, trillions of bacteria, yeast, cells, and cell parts, this bubble is actually more like a cloud—a cloud, new research suggests, that is unique to you.
According to a new study in the open-access journal Peerj, scientists can distinguish the make-up of the cloud is uniquely yours—a personal marker that is as particular to you as your fingerprints or your genome. That’s a biological calling card that could have implications for epidemiology, environmental engineering or even criminal forensics.
The new study was conducted by a group of investigators from the University of Oregon, led by environmental scientist James Meadow. The team already knew a lot about how readily human beings leave their microbial mark on their surroundings. Within just a few days of moving into a new home, for example, the occupants have already filled the air and seeded the surfaces with detectable microscopic organisms.
And while microbes shed outdoors may be quickly dispersed with the wind, microbes shed indoors—in what environmental scientists call the built environment—stick around and collect. Since people in industrialized societies spend an estimated 90% of their day indoors, that’s a lot of time for us to steep in one another’s overlapping clouds.
The Experiments
To determine how distinct those clouds are, the investigators ran two experiments. In the first, they had three subjects spend two hours one day and four hours the next sealed alone inside a sanitized sampling chamber. All of the surfaces within the chamber had been cleaned with antiseptics and the air had been filtered. If the chamber grew too hot or too cold, the temperature could be adjusted via heating coils in the floor—avoiding the contaminants that would be introduced by an air conditioner or a forced-air heater. At the end of the sessions, microbial samples were collected from several settling dishes placed near the subject.
In the second experiment, eight different subjects spent just 90 minutes at a time confined in the chamber. After that comparatively brief period, the air, not the surfaces, was sampled for microbes.
For simplicity’s sake, the researchers limited their analysis to 12 different bacterial families—including Staphylococcus, Streptococcus and Lactobacillus—which are common parts of a human microbiome and are usually found in higher levels in rooms people have occupied. Comparing the samples they collected from the chamber to samples they collected directly from each individual, they found that while all of the subjects emitted more or less the same collection of microbes, the ratios of each were indeed unique to the individuals.
“Our results confirm that an occupied space is microbially distinct from an unoccupied one,” the authors wrote, “and reveal for the first time that individuals occupying a space can emit their own distinct personal microbial cloud.” The differences among the samples ranged from as little as 4% of the bacterial population to as much 61%. The presence of one bacteria family alone—Lactobacillus—was sufficient to determine the gender of the occupant, because it is a microbe most commonly found in vaginal samples from healthy women.
What Our Microbial Signature Might Mean
Understanding the interplay between the microbial cloud and environment could form the basis for attempts to better engineer indoor spaces to prevent the transmission of diseases. We could potentially design our buildings around that. If we know there’s an airborne disease risk, maybe we could develop ventilation accordingly. Places like hospitals or offices could stand to benefit, for example.
Another potential real-world application for microbial cloud research is forensics. We already know, for example, how to distinguish between the bacterial fingerprints people leave on their computer keyboards. And while it may be years down the road, our ability to distinguish between people based on their airborne microbial signatures will likely get better and better.
We might also change our view of the people we share indoor spaces with. Given that we spend 90% of our lives indoors, our microbial clouds also colonize the places we live and work—and, yes, the people around us.