Midnight Riders: Microbial Life on the NYC Subway System

Have you ever wondered what kind of germs live on the poles of NYC subway cars?
Well ponder no more, for researchers at Cornell University have finally figured it out!

For this study, the researchers took over 1,000 swab samples at numerous locations (including poles, benches, handrails, and doors) in the New York City subway system, and then sequenced any DNA that they were able to pick up. They next compared these sequences to a database of DNA sequences that have been previously matched with specific strains of microorganisms. What they found was actually pretty interesting. For example, the Bronx is apparently a hot spot for microbial diversity, being the borough that had the greatest variety of microbes. Sorry Staten Island, but you came in dead last.

Now as you’d expect, the researchers found DNA sequences for infectious bacteria as well. Among them were Staphylococcus aureus (which causes staph infections), Bacillus anthracis (anthrax), Yersenia pestis (black plague), and E. coli (associated with fecal matter). Should you be worried though? Not at all. In fact, the E. coli strains they found were non-infectious. Meanwhile, Staphylococcus and B. anthrasis are commonly found in the environment and don’t normally result in infections. Finally, Yersenia pestis, though it was detected, really only infects 7 people per year with black plague in the US, and none of those cases were recently in NYC. But all those facts aside, we also can’t know if the DNA sequences they found were actually from live bacteria or not.

Now humans also have DNA and yes, they picked up some human DNA too. Interestingly, the profile of human DNA that they sequenced for each different location tended to match the demographic profile of that area. For example, genes associated with Hispanic ancestry were highly prevalent in one area near the Manhattan Chinatown where there are large populations of Hispanic residents.

What do the authors want to do with all this data? They hope that such large-scale studies of microorganisms can be used for forensic applications in the criminal justice system or in city-wide disease threat surveillance. They also discuss using their data, in combination with what we know about the human genome, to predict a person’s risk of infection, relative to the microbes present in their environment.

For even more information about the study, check out Elizabeth Harris’ story about it over at The New York Times.

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