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The day his young daughter licked the handrail while riding the Subway, New Yorker and physiology professor Christopher Mason wondered what kind of bacteria she'd encountered. So he sequenced all 468 subway stations for pathogens, using more than 1,500 samples, collected at three spots per station.
"The goal was to create a molecular map of the city," he says, much like the graph of the stops on the 1 Train, and its intersecting lines.
Mason's team built a mobile app to cross-reference the sample with its geolocation, timestamp and a photo of its place of origin. The research, which took 18 months from the summer of 2013, found more than 656 identifiable species. Microbes ranged from bacteria associated with food, insects, plants and (mostly benign) disease, to human DNA.
For instance, South Ferry is host to a number of bacterial species usually found in oceans, after it was flooded by Hurricane Sandy in 2012. And a bacteria named Pseudomonas stutzeri is found abundantly in soil yet is by far the most common bacterium on the NYC subway.
"We could see different types of cheese related to the pizzas that people eat," says Mason, 37.
These findings make up what Mason calls the "microbio signature" of a city. So, with the global project Meta-genomics and Subways and Urban Biomes (MetaSub), Mason explored other cities. Shanghai, Stockholm, Chicago, Tokyo and Boston were among the 51 cities where, in June 2016, MetaSub launched a co-ordinated sampling experiment, to be repeated in each city every year for the next five years.
"It's called metagenomic forensics," says Mason. "Once we've built these maps, we can tell where you come from based on the microbes at the bottom of your shoe."
This article was originally published by WIRED UK
