Your microbiome, your body’s commensal bacteria, is physically, biologically, part of you. If so, rather than being a single organism, you are actually a set of organisms; in fact, you are a superorganism.
Evolution has produced a synergism between host and its microbes that is critical for survival. It’s not just their weight (about 2 pounds) that makes them physically part of you: it’s that they function as an organized cellular system similar to, say, your immune system.
You are not merely a host composed of some ten trillion cells produced by some 23,000 human genes; you are also some one hundred trillion bacteria from several hundred species produced by some three million non-human genes. You are more than you thought you were.
Consider, for example, your ability to digest complex carbohydrates. Your microbiome in your gut processes them and yields small fatty-acid molecules that then pass through the wall of your digestive tract to be further processed by some of your body’s other biochemical processes into either energy or fat. Without your microbiome, your body would be unable to digest complex carbohydrates!
I’d say such a critical part of your digestive system is you. Don’t you agree?
(This is not as surprising as it might seem as soon as you realize that it is not necessary to ingest any carbohydrates for us humans to be healthy.)
Conventionally, your organism began as a fertilized egg that contained about 23,000 genes from your mother and father. Even physically, however, you are more than merely the descendant of that fertilized egg, more than a mere individual: you are an ecosystem.
You have been since infancy. Mother’s milk is loaded with carbohydrates called “glycans.” Only the bacterial enzymes of your microbiome can convert them into usable sugars!
Normally, there’s a healthy, win-win balance between a host and its microbiome. The microbes that live on and in you win by getting shelter and raw materials. So it’s normally in their interest to protect their host to continue feeding and living there. A healthy human adult hosts about one hundred trillion bacteria just in his gut! They are not freeloaders; they are not mere passengers. Nor are they parasites. They are integral parts of our physical systems.
Usually. Sometimes the balance between a host and its microbiome breaks down and this can cause disease, both acute infections as well as chronic illnesses.
With respect to acute infections, antibiotics are the greatest success story of 20th century allopathic medicine. They have often been able to turn the tide in favor of the host’s health during times of acute crisis. (Of course, the bacteria fight back by adapting and researchers have struggled to stay one step ahead of successful mutants—but that’s another story.)
With respect to chronic illnesses, researchers have only recently begun to think about new ways to restore imbalances. This provides rational hope for those suffering from, or at serious risk of developing, such diseases as obesity, diabetes, heart disease, asthma, multiple sclerosis, autism and some others.
There’s even more hope: genetic diseases are always incurable (and often very difficult to treat). It’s possible that what have been considered genetic diseases are not really genetic diseases at all. This is because it’s possible for infants to pick up microbiomes not only from their mothers but also from their immediate external environments. So what may have initially appeared to be a genetic disease may be an imbalance within the microbiome. This is good news because, unlike the human genome, the microbiome is not only accessible but medically treatable.
In terms of their mass, bacteria are and always have been, and probably always will be, the dominant form of life.
A phyla is a large biological category. There are about 100 phyla of bacteria. Bacteria from just 4 of them dominate your microbiome. Most bacteria cannot survive in such a specialized environment.
Once researchers began thinking of themselves as ecosystems (and not merely individual organisms), they quickly grasped the possibility of internal competition. After all, even relatively stable ecosystems like a rain forest that function well are not without internal conflict.
For example, the same processes that feed us can overfeed us, which results in obesity, or underfeed us, which results in malnutrition. It turns out that fat people have different ratios of certain phyla of bacteria in their guts than thin people – and that changing the diet can change bacterial flora! So, although it’s not the whole story, having the wrong kinds of ratios of bacteria in a sufferer’s gut may be a cause of either obesity or malnutrition. In this way, changing the way they think about the microbiome can lead researchers to potentially very fruitful research with respect to disease of nutrition.
It’s a similar story with respect to diabetes. Morbidly fat people sometimes undergo a Roux-en-Y surgical procedure that I’ve discussed elsewhere [click here to read that page]. It can be an effective treatment for obesity. What’s even more interesting is the fact that it is an extraordinarly effective treatement for diabetes: in 4 out of 5 patients, diabetes vanishes within days! Why? It may be that the ratios of bacteria in the gut may have changed.
There’s similar exciting research going on with respect to heart disease, multiple sclerosis, auto-immune diseases, and other diseases and conditions.
I’m neither a medical researcher nor a physician. What’s most interesting to me in the recent story of the microbiome is how intellectual flexibility can be very productive.
Although in practice there may be no person who is wholly a fanatic or wholly a philosopher, the distinction between the two is very useful. Fanatics are people so attached to their beliefs that they never even examine them seriously, whereas philosophers are so relatively detached from their beliefs that they are always willing to examine them (and re-examine them).
Most people think they understand themselves in the sense of knowing what they are, but, in fact, they lack a defensible view about their own nature. Until they question themselves, until they seriously ask “Who am I?” and “What kind of thing am I?”, they simply remain stuck on whatever indefensible beliefs they happen to have picked up. Once they open intellectually, however, new possibilities emerge that can lead to a new and improved view about what it is to live well.
Initially and naturally, we all identify with our bodies. However, when pressed, it’s not clear what “I” denotes or what people really mean when they use words like “my” or “me” or “mine.” It’s not clear exactly what a single organism is.
Instead of staying stuck on vague, popular concepts such as “organism” or “individual,” it’s almost always fruitful to examine them.
Being willing to revise your self-understanding can be extremely valuable – and not just physically.
AS ALWAYS , if you know someone who might benefit from reading this, please pass it along.
RECOMMENDED READING: The Economist (Aug 18-24 2012).