Space & Innovation

Cities Have Unique Bacterial Fingerprints

Human skin is the largest identifiable source of the bacterial samples, making up 25 to 30 percent of the microbiomes. Continue reading →

Used to be you knew which city you were in from the food, the sports team, the historic sites, even the local brew.

Now a team of microbiologists discovered they can tell cities apart by their unique bacterial fingerprints.

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The surprising finding was made after an intense study led by John Chase of Northern Arizona University's Department of Biological Sciences and Center for Microbial Genetics and Genomics. He and his colleagues spent a year swabbing for samples at nine offices in San Diego, Flagstaff, and Toronto.

They wanted to find out what kind of impact factors like geography, location in a room, seasons, and human interaction have on the microbial communities we spread around, called microbiomes. The researchers wanted to study microbiomes in the built environment, meaning bacteria around offices. Yeah. I can only imagine.

Their strategy involved installing the same carpeting, ceiling tiles, and drywall swatches in the various city offices to compare bacteria. In addition to swabbing those materials, they collected skin, nasal, oral, and fecal microbiome samples from office workers and the researchers doing the sampling. Science!

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First, their results showed that bacterial communities don't actually differ by the material in an office, but they do vary by location within an office. "Floor samples were significantly richer than either ceiling or wall samples," the researchers wrote in their findings. In other words, the floor is really grody. Don't sleep there.

Another conclusion was that human skin was the largest identifiable source of the samples, making up 25 to 30 percent of the microbiomes. The biggest finding, though, was that regardless of factors like season or office location, the microbiomes are city-specific.

In order to test their results, the team created a computer model that used machine learning to guess which city a particular sample came from based entirely on the microbes. Amazingly, their model, called a support vector machine, predicted the city of origin with 85 percent accuracy.

The team's results were published this week as an editor's pick in the microbiology journal mSystems. "...we find that offices have city-specific bacterial communities, such that we can accurately predict which city an office microbiome sample is derived from," the scientists concluded.

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Spring cleaning is a creepy reminder that dust is full of dead skin, and I try very, very hard not to think about that. So it's not entirely surprising that a bunch of people working together in an office would contribute to a unique microbial community.

What's truly weird to me is that these are a city-specific communities rather than office-specific ones. I guess that once a city gets under your skin, it's hard to simply brush it off.

via Co.Design

Images from satellites and spacecraft can provide big-picture perspective, as it were, on how cities develop and grow. Above is Earth's most populous city, Shanghai, as seen at night from the International Space Station. For more images and galleries, check out NASA's sprawling

Visible Earth



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