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Science has finally breached the abyss, the ultimate heart of darkness, the deepest jungle … the belly button.

In a report in PLOS One this week, researchers from a handful of institutions say that they have found more than 2000 bacterial and archaeal phylotypes in the navels of 60 volunteers — an average of 67 different bacteria types per belly button.

Using multiplex pyrosequencing of 16S rDNA libraries, the researchers examined the types of bacteria present in subjects’ bellybuttons, as well as their diversity, to see if the diversity in one sample group could predict the diversity in a second sample group. It did. Moreover, most of the 2000 types the group identified were exceedingly rare. Only six phylotypes occurred on more than 80 percent of the volunteers.

“The vast majority of the species — 2188 all told — lived on six or fewer people,” writes Carl Zimmer (who offered his own belly button to the group’s scrutiny) at his blog, the Loom.

According to Robert Dunn, the study’s leader, writing in a Scientific American guest blog, the group initially started examining belly buttons using bacterial culture methods, but then decided to team up with the University of Colorado’s Noah Fierer for a deeper molecular analysis.

“We expected that in employing this more complete method of sampling that the species in different belly buttons would become more similar from one belly button to the next (as we got a more complete sample of who was present in each). They got more different,” he writes, calling the findings a “terrible, yawning, richness of life.”

In one subject, who volunteered to Dunn that he hadn’t bathed in years, the team discovered not just bacteria, but also two species of archaea.

In a PLOS One blog highlighting the study, Dunn says that while the group “can now predict which bacteria tend to be frequent and common in belly buttons,” they are still “totally unable to predict which of the common species will be found on any particular person.”

According to Dunn, the group will soon have sampled more than 600 total belly buttons. Who knows what this larger cohort may reveal about the diversity and similarities of what he calls the intimate umbilical forest.

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