What lurks beneath? New York's subway system is a bacterial city beneath the city. Photo / Getty Images
Some 15,000 life forms were detected in DNA sampled from the turnstiles, keypads and seats of 466 of New York's subway stations. Most of it is what you'd expect: mozzarella, blowflies, staph — and anthrax. Then there's the weird stuff: Tasmanian devil, Himalayan yak and Mediterranean fruit fly.
But, that only accounts for half of the DNA collected and sequenced in the recent study of the thriving metropolis' underground biome (habitat).
The other half is, well … unknown.
Is the New York subway the closest thing on Earth to the primordial goop that first sparked life on this planet?
Or is it the favoured mode of terrestrial transport for extraterrestrials (the UN is based in New York, after all)?
The Wall Street Journalhas compiled the results of the New York subway network study by the PathoMap project into an interactive map.
Yes, there's a thriving metropolis of bacteria down there.
And it's even divided itself into communities.
It's all been made possible due to the increasing speed and ease with which DNA analysis can be conducted. Samples don't need to be big — simple scrapings will do. Your average lab can do the sequencing.
"We know next to nothing about the ecology of urban environments," evolutionary biologist Jonathan Eisen at the University of California at Davis told the Wall Street Journal. "How will we know if there is something abnormal if we don't know what normal is?"
And if you want to find something, a subway used by 5.5 million commuters every day is where you're going to find it.
They found more than 10 billion fragments of biochemical code, and sifted it through a supercomputer.
The only problem was the library of known DNA it was all matched to.
So, no. The unknown DNA isn't likely to be our evolutionary future. Nor is it likely to be the Illuminati, Daleks, Cloverfields — or any number of other alien life form that has invaded New York on our screens.
of that library are still largely bare.
So when a result matches 'no known life form', that's exactly what it means.
It simply hasn't been identified and catalogued yet.
Humans. Blowflies. Beetles.
The DNA of all of the above were found in abundance.
But not cockroaches.
That's because they've not been fully sequenced yet.
And why did the test throw up Tasmanian devils and Himalayan yaks — both somewhat unlikely to use the New York subway?
Because fragments of DNA can be similar between species. And an incomplete catalogue will throw up only what it knows.
This is why PathoMap later retracted its claims to have found anthrax and bubonic plague in the subway system: it blamed an 'error of interpretation' for the misdiagnosis.
The study has a serious side.
It is looking at what potentially harmful (disease carrying) bacteria is thriving beneath the city's streets, where it came from and how it got there.
It's seeded by the bacteria on the food commuters eat, the pets and plants they keep, carried by their shoes and clothes, and left behind by their trash, couches and unwashed hands.
More than half of the identified bacteria came from human gastrointestinal and urogenital tracts (faeces). About a third was the mostly harmless stuff that lives on our skin. Most of the remainder was associated with coughing or sneezing.
The scientists pointed out the levels of bacteria they detected in the subway system poses no public-health problem.
But the list of bacteria species they found at New York's 466 stations is revealing:
— 220 stations had traces of antibiotic resistant bacteria
— 215 had food-poising bacteria
— 192 carried urinary tract infections
— 151 had traces of mozzarella cheese
— 66 had meningitis and depsis
— 60 had saurcraut
— 37 were harbouring staph infections