When I first started paying attention it, the emerging science of the human microbiome estimated 500 species of microorganisms live with us in our gut and on our skin. Recently I saw that the estimate is now 20 times that—10,000 species share our life.
Each of us is a member of a very intimate ecology.
That intimacy is illustrated by an article to be published in next week’s ScienceExpress. Although for some time we’ve understood a good deal about the role that our gut microbiome plays in a wide range of activities—digestion, immunity, and mood to name a few—not so much has been known about our skin microbiome.
This latest research examines how the microbial colonies that inhabit our skin help keep our innate immunity working well. Innate immunity, of course, is the general-purpose response to a potential threat—inflammation, for example, is part of our innate immune response. So it’s not just our gut microbes that play a role in fighting off assaults—our skin microbes do too.
When our gut and skin microbes are out of balance, our innate immune system is out of balance, and the incidence of inflammatory diseases such as allergies and asthma increase. In fact, these diseases have been on the rise as populations have become more urbanized. To explain the connections, some researchers propose a biodiversity hypothesis, which is a descendant of the hygiene hypothesis.
The hygiene hypothesis argues that as populations become more urbanized, they become cleaner in the sense that they are exposed to fewer microbes and so their bodies are unable to develop the antibodies necessary to contend with provocative exposures. Antibodies are the product of the adaptive immune system, adaptations that are stimulated by an innate immune response.
The biodiversity hypothesis argues that lack of exposure to a biologically diverse environment stunts the development of our microbiome. What follows is an inadequate development of our capacity to resist and recover from immune challenges.
Biodiversity is also important on the small scale of your skin and gut. Remember that there are 10,000 species of microbes living with you in a cooperative and mutually supportive process. Of those numerous species, a few dominate—the Lactobacillus and Acidophilus of fermented foods and so forth. The remaining species, in contrast, are very low density. This form of microbial ecosystem is what’s called a rare biosphere.
The term “rare biosphere” was first developed in oceanography to describe the microbial ecosystems found in marine environments. I take great comfort in knowing that that I have yet another intimate connection with the life of the seas.
But to return to biodiversity and our microbiome, there’s good reason to believe that destruction of species and the simplification of ecosystems that seem to be overtaking us, in addition to being an environmental, food, and social justice issue, is also a health issue.
So, want to improve your health? Grow a rich, resilient, diverse ecosystem.
Into this picture I want to introduce something that’s going to add to your anxiety. Researchers are fast at work in a field called synthetic life. You’re familiar, of course, with organisms that have been genetically engineered—that is, a piece of DNA, often from an entirely different species, is slipped into the genome of a cell. Synthetic organisms are built from scratch. What’s troubling is that these new creatures come literally out of nowhere—or more accurately, out of someone’s imagination.
Genetically modified organisms are enough of a worry when it comes to biodiversity, but synthetic life, if released into the environment, could be worse because it has no biological context at all. Scientists are worrying about synthetic life: they’re having conferences and establishing protocols and standards and so on.
I sure hope they don’t make a mistake.
I was watching a flock of birds the other day, swirling through the air at breakneck speed, a fluid a cries and feathers. I’m confident none of those birds flies thinking it’s a member of the flock. Each one no doubt sees things and makes decisions from its own perspective: “I’m feeling a little nervous. I think I’ll fly over there.” Meanwhile, a whole set of environmental forces are at work on the flock—forces that neither the flock nor any of its birds can influence let alone control—guiding them toward good things and away from bad things… they hope.
The people who dream up things like synthetic life are in a flock that looks at science as something that’s supposed to make the world better. They don’t seem to understand the “the world” and “better” are contested terrain.
I prefer flocks that view science as revealing what’s in the world—like how many species of microbes are hard at work protecting me from illness.