Common Belly Button Bacteria
The most common skin bacteria encountered on participants in the Belly Button Biodiversity Project belonged to the groups Staphylococci, Corynebacteria, Actinobacteria, Clostridiales, and Bacilli.
For some of the common belly button species, we know a lot about their biology. Click the links below to read their species profiles in the Invisible Life Project:
For other common species, like Finegoldia and Anaerococcus, we know shockingly little.
In addition to identifying bacteria in samples by sequencing their DNA, we plated many participants’ samples on agar in order to provide them with a unique “portrait” of their belly button flora.
We can recognize some of the most common taxa in these portraits:
Bacteria can be beautiful. Some species of Micrococcus (M. luteus) produce yellow colonies, others (M. roseus) red ones, at least when grown in agar. Micrococcus species are aerobes; like us, they need oxygen. They are unlikely to do well too deep inside a belly button, but on the surface as elsewhere on our skin, they thrive. Micrococcus can deal with extreme drought and long periods of starvation. This toughness predisposes them to a life spent clinging to our desert-dry flesh.
The Clostridiales include bacteria like Anaerococcus and Clostridia. Some Clostridia species are bad news (think botulism), but most are harmless or even beneficial. The Clostridiales are anaerobes; they don’t use oxygen to make their way in the world. Individual microbes of this group are spindle-shaped and motile. They may be urging themselves across your skin right now, heading from inhospitable ground in a direction their simple senses tells them might be a better, some place like your belly button, or maybe your ear, though who can say. Like the stories of individual humans, the trajectories and fates of each individual bacterial cell on your body will be unique.
Like almost any bacteria in the wrong place, Staphylococcus species such as Staphylococcus epidermidis can become pathogens. Yet when living on your skin, Staphylococcus are far more likely to be beneficial, working as our first line of defense against pathogen invasion. S. epidermidis can use oxygen for respiration; however, when oxygen is in short supply (as it might be deep in your belly button), it switches to fermenting sugars. In other words, right now you might be making a teeny tiny bit of navel wine.
Right now wars are happening on your body. Bacteria are fighting other bacteria, fungi and even viruses. Among your skin’s true warrior clans are species of the genus Bacilllus such as Bacillus subtilis. Bacillus subtilis produces antibiotic compounds that can kill other bacteria and even foot fungi. Right now it may be doing this on your skin. We tend to think of the life on our skin as somehow stable and yet like any wild kingdom the individuals alive at any moment are the result of millions of independent wins and losses.