Mass transit as repository of microscopic organisms

A new study found all sorts of organic material in the New York City subway:

To get a clearer picture of what that ecosystem is made of, Mason and his team set out to map the vastness of the urban microbiome. Using nylon swabs and mobile phones, the group identified 15,152 different organisms lurking on railings, trash cans, seats, and kiosks in 466 New York City subway stations. Their findings were published this week in the journal Cell Systems.

The team also found that, on a microscopic level, the subway is littered with leftovers—evidence of what New Yorkers like to eat. Cucumber particles were the most commonly found food item, along with traces of kimchi, sauerkraut, and chickpeas. Bacteria associated with mozzarella cheese coated 151 stations. And other traces of pizza ingredients such as sausages and Italian cheese were everywhere. (The Wall Street Journal transformed much of that data into a clickable map that lets you explore the findings by subway line.)

And although Mason and his team also found particles of harmful bacteria related to the bubonic plague and anthrax, the levels were so low that they pose little danger to humans. “The important fact is that the majority of the bacteria that we found are harmless,” Mason said. Much more common were the protective bacteria that eliminate toxins and make the subway cleaner. “They represent a phalanx of friends that surround us,” he said…

Of the more than 10 billion DNA fragments that the team sequenced, about 5 billion were unaccounted for. That’s not to say that these DNA fragments belong to never-before-seen organisms. Rather, it shows that the library of sequenced genomes still has many empty shelves. Where beetles and flies were most prevalent in this sampling, evidence of cockroaches was absent—not because New York isn’t crawling with them (it is), but because scientists haven’t fully sequenced the cockroach genome yet. Once that information becomes available, cockroaches will become better represented in the sampling, according to Mason.

While I’m sure plenty of people will be grossed out by such knowledge, it highlights the level of microscopic complexity going on all around us and suggests there is a lot of scientific work in this area still be done. We know the bottoms of the oceans might be the last large frontier on Earth but it sounds like the NYC subway offers plenty of opportunities itself.

Now that we have such information about what is in the subway system, I want to know how the organic material interacts with humans on a regular basis. Where is this material? How many people are made sick and, conversely, does such a collection provide benefits for users?