Ever since we humans first discovered microorganisms many centuries ago, we’ve known that we’re in the presence of various types of bacteria and other critters that can’t be seen with the naked eye. In the time that has passed since this first discovery, our primary focus has been on eradicating microbes that make us sick. We’ve used tons of antibiotics, both in medical care and agricultural settings; designed various antimicrobial lotions in order to attack stubborn skin problems; and “sterilized” our homes using harsh cleaning detergents.
We’ve known for some time that not all bacteria are bad and that certain types of microorganisms positively affect our health; however, it’s only very recently that we became aware of the fact that microbes are integrated into pretty much every part of our biology.
The microbial self
Thanks to massive research projects such as The Human Microbiome project and the European Project MetaHIT (Metagenomics of the Human Intestinal Tract), in addition to thousands upon thousands of smaller studies, we now know quite a bit about the microorganisms that colonize the human body.
These research endeavors have changed our perception of what it means to be human.
For the longest time, we devoted virtually all of our attention to the human genome. What we’re now realising is that the human microbiome – the collective genetic material of all the microorganisms that colonize the human body – is in some respects even more important than the 23 pairs of chromosomes that are passed down from mothers and fathers to their offspring, affecting everything from our immune function to brain development to dietary preferences to social behavior (1, 2, 3, 4).
Microorganisms have co-evolved with us throughout our evolution, forging symbiotic relationships. The human microbiota may be considered an essential organ of the human body, because in the absence of microbes, the body doesn’t function correctly. With that said, it’s important to note that the microbes that colonize our bodies aren’t us. They are as much a part of our environment as the plants and animals around us. In other words, the microbiome can be thought of both as an organ and an environmental factor.