Life in Your Belly Button

National Geographic:

The whole thing started about two years ago. An undergrad's only-in-a-biology-lab idea—sampling colleague's navel bacteria for a holiday card—struck a chord with the North Carolina State University team, which had adopted a new focus on citizen science.

What better way to get the public interested in science than by showing them their skin's own thriving ecosystems? "And belly buttons are just ridiculous enough to appeal to almost everyone," Dunn added. . . .

From 60 belly buttons, the team found 2,368 bacterial species, 1,458 of which may be new to science.

Some belly buttons harbored as few as 29 species and some as many as 107, although most had around 67. Ninety-two percent of the bacteria types showed up on fewer than 10 percent of subjects—in fact, most of the time, they appeared in only a single subject.

There is a sense in which bacteria are still the normal form of life, since however you count they make up most of it. They also make up most of life's diversity, especially at the biochemical level. If they disappeared, we would be gone in days; if we disappeared, they would not notice.

Yes, they live on you, all over you. Get used to it.