Have you ever been on the subway and seen something that you did not quite recognize, something mysteriously unidentifiable?
Well, there is a good chance scientists do not know what it is either.
Researchers at Weill Cornell Medical College released a study on Thursday that mapped DNA found in New York’s subway system — a crowded, largely subterranean behemoth that carries 5.5 million riders on an average weekday, and is filled with hundreds of species of bacteria (mostly harmless), the occasional spot of bubonic plague, and a universe of enigmas. Almost half of the DNA found on the system’s surfaces did not match any known organism and just 0.2 percent matched the human genome.
“People don’t look at a subway pole and think, ‘It’s teeming with life,’ ” said Dr. Christopher E. Mason, a geneticist at Weill Cornell Medical College and the lead author of the study. “After this study, they may. But I want them to think of it the same way you’d look at a rain forest, and be almost in awe and wonder, effectively, that there are all these species present — and that you’ve been healthy all along.”
Dr. Mason said the inspiration for the study struck about four years ago when he was dropping off his daughter at day care. He watched her explore her new surroundings by happily popping objects into her mouth. As is the custom among tiny children, friendships were made on the floor, by passing back and forth toys that made their way from one mouth to the next.
“I couldn’t help thinking, ‘How much is being transferred, and on which kinds of things?’ ” Dr. Mason said. So he considered a place where adults can get a little too close to each other, the subway.
Thus was the project, called PathoMap, born. Over the past 17 months, a team mainly composed of medical students, graduate students and volunteers fanned out across the city, using nylon swabs to collect DNA, in triplicate, from surfaces that included wooden benches, stairway handrails, seats, doors, poles and turnstiles.
In addition to the wealth of mystery DNA — which was not unexpected given that only a few thousand of the world’s genomes have been fully mapped — the study’s other findings reflected New York’s famed diversity, both human and microbial.
The Bronx was found to be the most diverse borough in terms of microbial species. Brooklyn claimed second place, followed by Manhattan, Queens and Staten Island, where researchers took samples on the Staten Island Railway.
On the human front, Dr. Mason said that, in some cases, the DNA that was found in some subway stations tended to match the neighborhood’s demographic profile. An area with a high concentration of Hispanic residents near Chinatown in Manhattan, for example, yielded a large amount of Hispanic and Asian genes.
In an area of Brooklyn to the south of Prospect Park that roughly encompassed the Kensington and Windsor Terrace neighborhoods, the DNA gathered frequently read as British, Tuscan, and Finnish, three groups not generally associated with the borough. Dr. Mason had an explanation for the finding: Scientists have not yet compiled a reliable database of Irish genes, so the many people of Irish descent who live in the area could be the source of DNA known to be shared with other European groups. The study produced some less appetizing news. Live, antibiotic-resistant bacteria were discovered in 27 percent of the collected samples, though among all the bacteria, only 12 percent could be associated with disease. Researchers also found three samples associated with bubonic plague and two with DNA fragments of anthrax, though they noted that none of those samples showed evidence of being alive, and that neither disease had been diagnosed in New York for some time. The presence of anthrax, Dr. Mason said, “is consistent with the many documented cases of anthrax in livestock in New York State and the East Coast broadly.”
The purpose of the study was not simply to satisfy scientific curiosity, the authors said. By cataloging species now, researchers can compare them against samples taken in the future to determine whether certain diseases, or even substances used as bioterrorism weapons, had spread.
City and transit officials did not sound grateful for the examination.
“As the study clearly indicates, microbes were found at levels that pose absolutely no danger to human life and health,” Kevin Ortiz, a spokesman for the Metropolitan Transportation Authority, said in an email. And the city’s health department called the study “deeply flawed” and misleading.
Dr. Mason responded by saying he and his team had simply presented their complete results.
“For us to not report the fragments of anthrax and plague in the context of a full analysis would have been irresponsible,” he said. “Our findings indicate a normal, healthy microbiome, and we welcome others to review the publicly available data and run the same analysis.”
Thanks to Kebmodee for bringing this to the attention of the It’s Interesting community.