Did you know that you can think of yourself as a rainforest? An ecosystem of multitudes? A home for countless species engaged in trillions of invisible interactions happening in and on your body—in short, a superorganism?
We are a home for trillions of microbes - bacteria, fungi and viruses - our microbiota, whom we are tightly connected with. Probably more tight than you would think.
David Relman writes in his 2012 Nature article “the dawn of the twenty-first century has seen the emergence of a major theme in biomedical research: the molecular and genetic basis of what it is to be human. Surprisingly, it turns out that we owe much of our biology and our individuality to the microbes that live on and in our bodies — a realization that promises to radically alter the principles and practice of medicine, public health and basic science.”
Microbes affect our individuality. Our health is directly intertwined with that of our microbial partners.
There is only one other organ in the body that can compete with the gut for diversity — the brain. The gut’s network of nerves is just as large and chemically complex.
There is the growing body of research indicating that our intestines may have a far greater influence on our feelings, decisions and behavior than previously realized. The primary evidence for this, is the vast network of nerves attached to our guts that monitors our deepest internal experiences and sends information to the brain, including to those regions responsible for self-awareness, memory and even morality.
About 95% of the serotonin (the happiness hormone) we produce is manufactured in our gut, where it has an enormous effect on both mood and GI activity.
Not long ago humans used to think that a good bacteria is a dead bacteria. But by today scientists have concluded that only about 0,1% of microorganisms living inside the human body are possible pathogens. The rest are either necessary for us, or their function is unknown.
Although most of our body parts are "inhabited" by microbes (our skin, respiratory tract, mouth..) about 99% of bacteria live in the gut.
Our microbiota consists of about the same amount of cells that we have our own human cells. But these cells are smaller and lighter, so the microbiota together weighs about 2–3 kg.
However, genetic diversity of the microbiota is much more important. We humans have about 23 000 different genes in our genome (our total DNA). At the same time, microbes living inside a human body have a total of 2–20 million genes.
Therefore we are carrying around a world of bacteria that has a genome 100 times the size of our own. These genes have many different functions and help to adapt in different conditions. Our microbes compensate for what is beyond our genetic capacity.
So next time you choose what you want to eat, think and speak, consider that you might not only be influencing your brain but also your gut, including trillions of microbes.