Behold, the great umbilicus, most commonly referred to as the belly button. Whether you are sporting an “innie” or an “outie”; one fact remains. Found within the human naval cavity is an incredible number of bacterial phylotypes (or “species”) and even on the very rare occasion, archaea, that has captured the attention of many scientific minds.
There are several groups of scientists that have decided to sample and research what could exist in the folds and wrinkles of this shared physical trait, and to elucidate the bacterial phylogenetics using both microbial techniques and next generation sequencing. One such group published their findings in a paper titled “A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable,” in which scientists studied the next generation sequencing results of over 500 belly button swabs, including a sample swab from an individual’s belly button who had not showered or bathed for several years.
There literally exists trillions of individual bacteria that live on the organ that is the human skin. The belly button provides a unique environment in contrast to the outer surface area of the skin, in that the belly button tends to be less directly washed (as opposed to your hands) and thus creating a moist, dark, and warm little pocket in which certain phylotypes of bacteria (and the rare archaea) thrive. Out of the 500 samples collected for DNA sequencing, the scientists involved in the study, which this summary focuses on, initially focused on 60 samples that were the first collected. The genomic DNA from each pellet of a belly button swab was extracted using the Qiagen PowerSoil DNA Extraction kit. Amplicon libraries for each genomic sample were created using PCR universal bacteria and archaea 515F/806R primers, and each post-PCR library cleaned with a PCR clean-up kit and prepped for subsequent DNA pyrosequencing.
From just these 60 samples analyzed through next generation sequencing, almost 2400 total phylotypes were elucidated, in which over 90% of them were seen in less than 10% of the samples collected, and only 8 phylotypes were shared amongst over 70% of the belly buttons studied. Of special interest were the three different archaea phylotypes that were identified, two of which came from the belly button of the unwashed sampled individual. During the time of this study, archaea had never been reported as having been found on human skin and is characterized as only having been identified from samples in extreme environmental conditions.
The human umbilicus is most assuredly a haven to many, many different types of bacteria, and previous practices of identifying belly button phylotypes relied upon colony growth on Petri dishes. Since the vast majority of the little critters that thrive in the button cannot be cultured using standard microbial techniques, this leaves an avenue of research that can be further studied in greater depth through the continued advances of next-generation sequencing. It is indeed a jungle in there!