Last week, in an issue of Nature Microbiology, we got a glimpse at the new, revised tree of life: a sprawling, unruly diagram that proved just how little we know about the world around us. All of the organisms we normally think of—animals and plants—are only a tiny fraction of the whole story. Most of the billions of life forms on Earth are bacteria.
A new era of scientific discovery is emerging—one that combines microbiology and our newfound ability to collect and process the microbial life around us and inside of us. In fact, you have a unique community of microbes that you carry around with you—scientists call this your "microbiome" and estimate it contains 100 times the amount of genetic information as your actual DNA. These bacteria affect everything from your digestion to your skin, and companies are already racing to market products that enhance the natural effects of your own vibrant microbial community.
Now, a paper published this week in the microbiology journal mSystems shows that even cities have their own unique bacterial fingerprints, too—as do offices. And yes: Your phlegmy coworker is part of it.
The researchers, led by John Chase of Northern Arizona University’s Center for Microbial Genetics and Genomics, wanted to study the microbial communities in offices—reflecting a growing interest in the microbiomes of built environments, or "BEs" as they’re often abbreviated in research. "We know that microbes in the [built environment] affect human health," they explain. "However, until recently, very little was known about the microorganisms that cohabit with us in these environments."
To study them, they started spec’ing.
They chose a specific type of carpet, a ceiling tile, and a brand of drywall to install in nine different offices across three cities—San Diego, Toronto, and Flagstaff—each in a different climate zone. Using the same material allowed them to compare whether, say, the floor under your desk is teeming with more bacteria than your wall. (Yes, it is.)
They also collected very personal samples from office workers—not only skin, snot, and saliva, but also fecal matter—to find out how their unique microbiomes affected the office’s. Then, over the course of a year in each office, the team collected bacterial samples from each architectural material swatch, creating a calendar of the office’s bacterial ebb and flow.
What did they find? First of all, that our offices are fairly hermetic spaces. These tightly controlled environments are "microbial wastelands" and "desert-like environments where microbes passively accumulate," microbiologist Sean Gibbons writes in a commentary published with the study. "Humanity’s transition from the outdoor environment to the built environment has reduced our exposure to microbial diversity." In fact, a lot of the microbes came from humans—about 30% from human skin, while a "small but consistent" amount from nasal matter.
But the team also decided to run an unusual test on the results: They created an algorithm that guessed which city a sample came from based on its microbes. Shockingly, it could guess with 85% accuracy—while within a given city, it was pretty bad at telling the specific offices apart.
That would suggest that each city has its own unique signature of bacteria, influenced by its people, its environment, its infrastructure, and its weather. Just as we think of humans from New York or Los Angeles as having certain relatively common characteristics, the microbial populations within cities might share some proclivities, too.
But truly understanding these types of communities will be a decades-long endeavor. As science journalist Sarah Zhang discovered when she had the microbiome of her apartment sequenced last year—and found that much of it was "unclassified" or unknown—this is an emerging field and an emerging technology.
So for now, the details of these vast urban oases of bacteria will remain largely unknown beyond the fact that they do indeed exist, resting just beyond the reach of our current technological capabilities. We're standing at the brink of discovering this new world—one that we can't see but that flourishes inside us, our buildings, and even our cities.