The microbial community in the ground is as important as the one in our guts.

We have been hearing a lot recently about a revolution in the way we think about human health — how it is inextricably linked to the health of microbes in our gut, mouth, nasal passages, and other “habitats” in and on us. With the release last summer of the results of the five-year National Institutes of Health’s Human Microbiome Project, we are told we should think of ourselves as a “superorganism,” a residence for microbes with whom we have coevolved, who perform critical functions and provide services to us, and who outnumber our own human cells ten to one. For the first time, thanks to our ability to conduct highly efficient and low cost genetic sequencing, we now have a map of the normal microbial make-up of a healthy human, a collection of bacteria, fungi, one-celled archaea, and viruses. Collectively they weigh about three pounds — the same as our brain.

Now that we have this map of what microorganisms are vital to our health, many believe that the future of healthcare will focus less on traditional illnesses and more on treating disorders of the human microbiome by introducing targeted microbial species (a “probiotic”) and therapeutic foods (a “prebiotic” — food for microbes) into the gut “community.” Scientists in the Human Microbiome Project set as a core outcome the development of “a twenty-first century pharmacopoeia that includes members of the human microbiota and the chemical messengers they produce.” In short, the drugs of the future that we ingest will be full of friendly germs and the food they like to eat.

But there is another major revolution in human health also just beginning based on an understanding of tiny organisms. It is driven by the same technological advances and allows us to understand and restore our collaborative relationship with microbiota not in the human gut but in another dark place: the soil.