This project, named PathMap and led by Dr. Christopher E. Mason, a geneticist at Weill Cornell Medical College, was born out of his interest in watching his toddler-aged daughter place objects in her mouth as she explored new environments. For over 17 months, a variety of students and volunteers visited all Metropolitan Transit Authority (MTA) stations in order to create a “genetic profile” of the city’s subway system. They collected DNA from a variety of surfaces including, seats, doors, poles, turnstiles and benches, eventually identifying over 15,000 life forms.
From this large number, the group was able to further identify 562 types of bacteria, 67 of which could be dangerous to humans. In other words, nearly half of the DNA in the subway system is unknown to scientists and only 0.2 percent matched the human genome–statistics seemingly scary enough to make a germophobe out of the most dirt-loving individual.
Still, bacteria are not necessarily a problem. According to the Wall Street Journal, a typical individual is home to approximately a hundred trillion microbial cells or approximately 5 pounds of microorganism for each individual. In fact, microbial cells (both inside and outside the body) outnumber human cells 10 to one.
But some of the recovered DNA was not derived from harmless species. These less friendly bugs includedÂ an antibiotic resistant bacteria called Stenotrophomonas maltophilia, which was present in 409 stations, and another antibiotic resistant microbe called Acinetobacter baumannii, found in 220 stations. Other bacteria included those that cause food poisoning, urinary-tract infections, meningitis and sepsis, staph infections and tetanus.
Dr. Mason, however cautions that he hopes to intrigue people and not terrify them, though he acknowledged some people might be “unsettled.” Also upset was the New York City Department of Health and Mental Hygiene, which argued that the bacteria identified by the Cornell team were not done properly. In a statement, the organization wrote, “The interpretation of the results are flawed, and the researchers failed to offer alternative, more plausible explanations for their findings. The NYC subway system is not a source of plague or anthrax disease…”
Interestingly, for all the biodiversity identified on the subway, it is not as rich as the diversity found in normal soil. In fact, the dirt in Central Park contains 167,000 types of microorganisms, though how many of them are potentially dangerous are unknown to the author.
(Photo courtesy of Sakeeb Sabakka)