Every City Has A Unique Microbial Community

It turns out that cities have microbial signatures that make them unique. Scientists have found that communities of microbes within a city don't vary much, but between cities, they do.

Samples of microbes were studied in nine offices in three North American cities. Monitoring them for a year in Flagstaff, San Diego and Toronto helped scientists to install three sampling plates---one on the floor, one on the ceiling and the third on the wall.

By also installing sensors in various sites, scientists could monitor parameters of the environment, such as relative humidity, light, occupancy and temperature. The researchers gathered samples over four to six weeks.

"We suspect that in the absence of extreme conditions like flooding, microbes may be passively accumulating on surfaces in the built environment rather than undergoing an active process," said J. Gregory Caporaso, one of the researchers involved in the study from the Northern Arizona University in Flagstaff. "As we continue to expand our understanding of the microbiology of the built environment, possibly including routine monitoring of microbial communities to track changes that may impact human health, our results will help inform future research efforts."

More microbial samples were found on the floor, rather than on the wall or the ceilings. The rich microbial communities were found in Flagstaff offices compared to those in San Diego or Toronto. Over nine offices, researchers discovered that human skin bacterial communities characterized the microbial communities.

However, there were not too many differences inside cities, but more between them.

"This was especially interesting because even within each city, the offices we studied differed from each other in terms of size, usage patterns and ventilation systems, suggesting that geography is more important than any of these features in driving the bacterial community composition of the offices with the ranges that we studied," Caporaso said.

More information is available about the bacterial communities in offices, which may enable researchers to find out which location the bacteria originated from.

The findings were recently published in the journal mSystems.