Navel gazing – microbial style

Rob Dunn of North Carolina State University has written a charming and fascinating piece on the microbes that inhabit our belly buttons. You can find it here on the Scientific American blog site (

I strongly recommend it for the skill of his writing as well as the extremely interesting insights into the microbes in our navels, how they differ and some educated guesses as to why.

Dunn’s post got me thinking more about my recent speculation about the interconnectedness of our skin and the microbiome of the human skin, the “skin” and the microbes on the surfaces of the rooms we inhabit, and the climate in our indoor spaces. For more on this, see Grice and Segre’s review of the Human Skin Microbiome in Nature Reviews, (April 2011, Volume 9, 244-253).

I am reasonably convinced that the indoor environment influences the distribution of microbes that live on us — through effects primarily of temperature and humidity but also chemical qualities, the kinds of things Charles Weschler and others have been studying in the indoor environment. Charlie suggests that the chemistry that occurs in indoor air influences the surfaces of the building, and I have extended that notion to the surfaces of the human body.

Sure, clothes are important, so their care, frequency of washing and changing, etc., matter. Our diet and activity levels probably play a large role too.

And since Jordan Peccia and Bill Nazaroff and their students have shown that the bacteria found indoors are strongly influenced by what comes from our bodies, then there is a dynamic process at work where we really are part of the ecosystem that we call the indoor environment. (See Hospodsky et al 2012 PLos One article). We shed our skin every two to four weeks, and we have approximately 2000 micro-organisms per square centimeter of skin surface area. Charlie Weschler’s work has shown that the surfaces of an occupied space are covered with skin oils that are part (1% by weight) of shed skin cells. (See a video of his Lawrence Berkeley Lab Distinguished Lecture on Youtube). Shouldn’t we expect that all the surfaces also coated with bacteria that dwell on those shed skin cells?

What’s challenging for me is to bring together a comprehensive focus since most of the studies are dominated by a single disciplinary focus. Ecologists should be interested since they “get it” that it is a system with all of its interacting components and that many disciplines are necessary to create a complete picture. Any suggestions for how we might pursue this are welcome.

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