Jiri Hulcr and Andrea Lucky, two microbiologists from NCSU, collected 95 belly button swabs as part this biodiversity study. The pair isolated a whopping 1400 strains of bacteria, 662 of which may be new species not yet described by science.
Before you start freaking out and scrubbing your belly button to get the bugs out, most of the bacteria just exist there happily and do not cause an infection. Other than the ick factor, there is no need for concern. [Belly Button Biodiversity via Discover Magazine]