A new study reveals how cities in North America apparently possess not only unique cultural and economic characteristics but also, their very own distinct microbial communities. 

In this new study, researchers studied samples of germ specimens from nine different offices and work spaces from three cities in North America. Scientists discovered that human skin can also greatly affect the bacterial composition of surfaces indoors and office floors possess more germs as opposed to other surfaces, that are most likely caused by dirt from soil and shoes.

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According to author of the study, professor of biological sciences , J. Gregory Caporaso from the Northern Arizona University, this significant presence of germs is due to the absence of extreme environmental conditions outdoors like flooding, where microbes just continue to accumulate on surfaces inside the office environment as opposed to evolving into an active process.

This continuing process to learn more about microbiology and microbial communities in a human made environment can provide crucial insight about impacts on human health that can help future research efforts.

Researchers examined three offices during a one year period on Flagstaff, San Diego and Toronto. Each office had three sampling plates located on various locations, the floor, the ceiling and on the wall. Each of these plates had two or three swatches each of drywall paint, a ceiling tile and carpet that are all equipped with sensors as the team observed the parameters of the ecosystem indoors, such as humidity, light, occupancy and temperature.

The results revealed that there are more microbes on the floor specimens compared to walls or ceilings, where each city has its own distinct microbial community. The Arizona microbes were more dense and rich, while Sand Diego and Toronto microbes where more similar to each other.

Caporaso says that this is remarkable since each office in each city, were totally different in terms of size, usage and ventilation systems, suggesting that geography is a crucial factor that drives the bacterial community composition, within the studied ranges.

The team also discovered that indoor variables did not affect the richness of indoor microbial communities but found out that human skin are the one of the biggest sources of office microbes, making up a total of 25 to 30 percent of office germs. This new study is published in the journal mSystems.