There has been a rather recent realization that the human body is colonized by a whole host of various microbes. Some estimates are that there are as many as 10 times as many microbes cells than our own cells.
And they often serve an important function.
It turns out that many of these microbes protect us. Our bodies actually produce proteins to feed the good ones. By helping to keep the good ones healthy, that protects us against the bad ones.
Within our bodies, there are good gut bacteria that help us digest food, and that keep out (or at least keep under control) less benign bacteria. One problem with taking antibiotics is that they often kill the good bacteria along with the bad, and then when bacteria re-establish themselves, the good bacteria may be at a disadvantage.
Rob Dunn is the author of The Wild Life of Our Bodies, a pretty good book that details what we know about the microbiome. He also writes an occasional column for the Scientific American blogs, and in one of them, The top 10 life-forms living on Lady Gaga (and you), he talks about feet.
Here’s how that starts out:
We’ll start at the bottom. At least from a distance, feet can be lovely. They bend and twist to hold us up and move us over the world. Each foot is composed of 26 bones, every one intimately articulated with one or more others. But confronting a foot toe-on presents dirtier realities. The feet contact everything we hold our snootier noses up and out of (one feels, for the poor ants who must taste, in part, with their tarsi). Even when they are fully cloaked in socks, shoes, or–if you are Gaga–feathers, they are still a biome unto themselves. They are tougher and warmer, but also damper than most of our parts. With tens of thousands of sweat glands per inch, our feet sweat to excess. They are the poor man’s rain forest and like the rain forest, they abound in fungi. But it is not just any fungi that grows around our toes. Oh no, it is a special one. Tricophyton rubrum, the most common foot fungus, feasts on dead skin and toenails. It, or one of its close kin, is worn by many of us, perhaps most, of us. It blossoms from our flotsam. Every so often, when its garden grows too much, it becomes “athletes foot”; fungal bodies grow like the leaves of grass and as they do, the toe nails yellow and the skin cracks. But most of the time T. rubrum’s growth is moderate.
Hmmm. It appears he isn’t just talking about feet, he’s talking about shod feet. I bet those who go barefoot have an entirely different microbiome.
And when he talks about athlete’s foot, that’s a perfect example of how we have changed out microbiome to our detriment (in the same way that antibiotics might, as I noted above).
He also talks about another way the feet’s microbiome has been changed to our detriment:
Alongside the filaments of our fungi live bacteria. The bacteria on our feet consume the amino acid leucine found in sweat. It is these amino-acid-eaters that cause feet to stink. In eating leucine, these creatures excrete a gaseous perfume (isovaleric acid) that is instantly recognizable as it rises up from under the table. The stinking bacteria on most of our feet are Staphylococcus epidermidis, but those of us with especially stinky feet may also host another species of bacteria, Bacillus subtilis, which, despite its name, stinks with a ferocious lack of subtlety.
It is only shod feet that stink. The bacteria he mentions need that environment inside a shoe to really grow. They stay under control when feet are left bare.
Let me finish up with just a bit of humor. Cul de Sac is another cartoon I quite enjoy. The cartoon from July 21 is a perfect illustration for this entry.