Why do we wash our hands after we’ve been riding on public transportation? Is it true that “using the handrails on the subway is like shaking hands with 100 people”? New York City-based typographer and designer Craig Ward heard that urban legend and, inspired by this petri dish handprint created by Tasha Sturm, wanted to test it.

In this video from Science Friday, we tour a few subway lines around New York City via his bacteria samples — lots of harmless and beneficial normal flora, as well as a few more suspicious characters. It’s a surprising (or perhaps not so surprising) portrait of a bustling city.

Want to make your own bacterial art? Check out Strum’s How-To comments at MicrobeWorld.org.

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