We already know that New York City’s subways are hardly the beacon of cleanliness. After all, they’re frequented by 1.7 billion people each year who drag in their grubby hands and dirty boots. But after swabbing all those seats, railings and turnstiles, scientists have discovered an urban ecosystem that’s more diverse than you could imagine. More than 15,000 different species were detected in this busy underground world, almost half of which were bacteria. The team even discovered traces of the bacteria that cause bubonic plague and anthrax.
Far from just wanting to gross out germaphobes, the brains behind the new study hope that regularly monitoring the microscopic wildlife here will help scientists find new ways to track disease outbreaks. Furthermore, the information could help researchers detect bioterrorism attacks and fight the ever-growing problem of antimicrobial resistance.
The immense study, which has been published in Cell Systems and described in The Wall Street Journal, was conducted by scientists at Weill Cornell Medical College who had the laborious task of sampling New York’s 466 open subway stations, alongside one closed station. As you can probably imagine, this wasn’t the most pleasant task at times. As eloquently described in WSJ:
“The Cornell scientists and student volunteers gamely dodged rats and gingerly worked around discarded pregnancy tests, used condoms, puddles of vomit and rotting food to swab surfaces in every subway station.”
In total, 1,457 samples were collected across NYC, obtained from turnstiles, benches, kiosks and garbage cans. The genetic material in the samples was then sequenced and sorted by a supercomputer, and the results were compared with genome databases of the known inhabitants of Earth, including bacteria, viruses, plants and animals.
15,152 different organisms were detected from the fragments of DNA, almost half of which did not match any known species, highlighting how little we know about the microbial world around us. Of those that could be assigned to a particular organism, around half were bacterial DNA sequences. More than 550 different species of bacteria were identified from the samples, and although most were not harmful, 67 of these are associated with disease. However, these potential pathogens were found at such low levels that they were unlikely to be able to cause illness.
Interestingly, in South Ferry Station, which has been closed since 2012 after it was flooded, the scientists found bacteria that had only previously been isolated in Antarctica. Three different stations also yielded DNA from the bacterium that causes the plague, Yersinia pestis. This probably came from rats, which are known carriers of the bug.
The results even told a story of what New Yorkers like to fill their bellies with. Alongside identifying bacteria associated with the production of mozzarella cheese, they found lots of DNA from chickpeas, which could indicate a taste for falafels and hummus, and also cucumbers.
If you’re interested in finding out more about the wonderful diversity of DNA that the researchers found, The Wall Street Journal has published a cool interactive map that lets you look at the discoveries in each different area. It’s pretty interesting, but it may leave your skin crawling.