(Photo courtesy of Northern Arizona University)

A configuration of the sampling site in a Flagstaff office. The study set up similar configurations in offices in other cities.

The microbial communities in offices are generally similar — as long as those offices are in the same city. But every city has its own microbial fingerprint, according to a study led by Northern Arizona University.

Biologists sampled offices in Flagstaff, San Diego and Toronto. They used DNA sequencing to identify microbes on the floors, walls and ceilings.

Each city had a unique microbial community — so unique the scientists could predict the origin of an unlabeled sample just by looking at the microbes. 

John Chase is the lead author of the NAU study.

“My working hypothesis would be that the differences we’re seeing in cities are being driven by the microbes in the environment around the city,” he said. “I would expect that any city with different climates would have sort of a unique microbial fingerprint.”

People drive the composition of office microbes as well. A quarter of the microbes sampled came from human skin.

Chase suspects offices have mostly dead or dormant microbial communities, because the microbes didn’t react to changes in humidity or temperature during the experiment. NAU scientists plan to test that hypothesis next.