Almost half of all DNA present on the subway’s surfaces matches no known organism.
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Hundreds of species of bacteria are in the subway, mostly harmless. More riders bring more diversity.
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One station flooded during Hurricane Sandy still resembles a marine environment.
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Human allele frequencies in DNA on surfaces can mirror US Census data.
Summary
The panoply of microorganisms and other species present in our environment influence human health and disease, especially in cities, but have not been profiled with metagenomics at a city-wide scale. We sequenced DNA from surfaces across the entire New York City (NYC) subway system, the Gowanus Canal, and public parks. Nearly half of the DNA (48%) does not match any known organism; identified organisms spanned 1,688 bacterial, viral, archaeal, and eukaryotic taxa, which were enriched for genera associated with skin (e.g., Acinetobacter). Predicted ancestry of human DNA left on subway surfaces can recapitulate U.S. Census demographic data, and bacterial signatures can match a station’s history, such as marine-associated bacteria in a hurricane-flooded station. This baseline metagenomic map of NYC could help long-term disease surveillance, bioterrorism threat mitigation, and health management in the built environment of cities.