This episode is sponsored by Skillshare. [INTRO ♪].

I have a secret to tell you:. The device you're watching this video on is covered in microbes.

There are millions of little bacteria, fungi, and other tiny, microscopic things squirming around all over it. But, you can put away that hand sanitizer. Because microbes are all around us, all the time, and even the ones found in places that we think of as filthy and disgusting—like the New York City subway—are usually harmless.

We often see big scary headlines when studies looking at microbes get published. You know, ones like “Your Cell Phone Is 10 Times Dirtier Than a Toilet Seat!” But the truth is, microbes are everywhere all the time. And for the most part, that's really OK.

You're probably most familiar with the microbes that can make you sick—they're sometimes called pathogens. But there are a lot of microbes that don't affect humans at all. And a ton of microbes can actually be good for us.

Some are even necessary for our bodies to work. Human digestion, skin health, and so much more depend on and can be supported by, quote, “good” microorganisms. So while bacteria might sound like a dirty word, it's really not.

And a study of the New York City subway from 2015 shows why. See, a research team at Cornell sampled the New York City subway system and found microbes that didn't exactly line up with the subway's “gross” reputation. A team swabbed subway cars, stations, handrails, kiosks, and about every piece of every subway station in New York City—466 stations in total.

They then used DNA sequencing to figure out what was living on these surfaces. While you might expect a place like the subway to be riddled with disease-causing bacteria, the researchers found the exact opposite. Most of the microbes they found were harmless.

For example, the researchers found a lot of Lysinibacillus sphaericus, a bacterial parasite of insects that isn't harmful to humans or other animals. And the team even spotted some good microbes: ones that are often found in healthy human microbiomes. The team did specifically look for pathogens, too, and at first they seemed to find them at low levels in several places.

But a closer analysis of the data revealed they were just bacteria related to pathogenic species, not ones that are really dangerous. As they worked, the team also meticulously logged their samples in a special mobile app that they built. This let them create a map of all of the microbes in the city.

The idea is that this map would be used to monitor these microbes going forward so that if there was a dangerous outbreak or even a bioterrorism threat, it could help emergency responders figure out where to act. They'd know if a microbe was new to an area, for example. Or what other areas tend to have related microbes, and therefore might be more connected than geography would suggest.

Realizing the full potential of such a map will require more data, but it's already revealing some interesting things about the New York City subway— like, that the microbes which inhabit a particular area often reveal detailed information about what has happened there. Take the South Ferry subway station, for example. While it looks like your typical subway station, it was full of microbes more commonly found in the ocean.

That's because, in 2012, the South Ferry subway station was fully submerged during Superstorm Sandy, and the microscopic marine species that washed in were still living there three years after the flooding. They also found hot-spots of microbes associated with certain foods—like the bacteria that ferment Kimchi and sauerkraut. Basically, an area's favorite foods were reflected in the subway station's microbes.

This study and others continue to show that there's so much more going on around us than we realize. Living things that we can't see with the naked eye are everywhere, and there's still a lot left to learn about them. In fact, about half of the microbe DNA the researchers sequenced didn't match any known organism.

These mysterious microbes show just how little we know about our microscopic companions. But one thing we do know is that they're everywhere, and for the most part, they don't cause us harm. So, yeah, your phone might be teeming with bacteria and places you think of as grimy, smelly, or just plain gross probably are full of microbial life.

While I wouldn't go around licking turnstyles or anything, if you did, most likely, the bacteria living there wouldn't do you any harm. And that's more broadly true of basically everything that's quote “covered in microbes”. Which is, well ... everything.

Not only are microscopic organisms all around us, some of them are downright useful. If you're a baker, for example, you already know your creations depend on helpful microbes. And if you're not a baker but wish you were?

Well, Skillshare can help. You see, over 7 million creators are learning with Skillshare. And there are tons of classes that can help level up your cooking—like chef Julia Turshen's class on Easy and Versatile Baking.

In it, you'll get to know yeast—the microbe that helps bread rise—so you can become a better baker yourself. And there are over 25,000 other courses on Skillshare, so you can try your hand at everything from dough-making to interior design. And the first 500 SciShow viewers to sign up using the link in the description will get a 2 month free trial.

Yes, you heard that right—FREE. And you'll be helping support SciShow when you do it, so it's a win-win all around. [OUTRO ♪].