Our bellybuttons are home to hundreds of undiscovered species

The Belly Button Biodiversity project recently began taking DNA samples from people's navels to find out what bacteria is living within. Of the roughly 1,400 bacterial strains discovered thus far, at least 662 of them are completely unknown.

We wrote about the North Carolina State project a couple months back, and now the initial results on their first human investigations are in. The researchers swabbed the bellybuttons of 95 volunteers, and then used the 16S ribosomal RNA of the various bacterial strains to identify them. Using that method, they found they couldn't even identify the family, let alone the species, of hundreds of microbes, which strongly suggests they were previously unknown.

That's a dramatic result, but the researcher say it shouldn't necessarily be considered too surprising. Indeed, they say it's a testament to just how little we actually know about bacterial diversity. Team member Jeri Hulcr says this is the microbial equivalent of European explorers setting eyes on African game for the first time - once you get used to the fact of their existence, they quickly stop seeming all that exotic.

This also throws into high relief just how difficult it can be to properly identify bacterial species. The current benchmark for microbes is that any two strains that share 97% identical 16S ribosomal RNA are part of the same species...a standard that, if applied to mammals, would mean cats and dogs would be considered the same species. That ignores millions of years of divergent evolution in the mammals, and there's reason to think a similar finding in bacteria is just as ignorant of the strains' respective evolutionary paths.

Either way, for all this huge diversity and wealth of undiscovered species, our bellybuttons still feature a lot of familiar faces. In fact, the same forty or so species account for 80% of the bacteria in our navels, and the researchers hope to now find out whether these represent the "good, core biome of bacteria" while the others are more like unwelcome strangers, posing a threat to us by their mere existence in the bellybutton.

Via New Scientist. Image by fleshheadfilms on Flickr.