THIS IS A MICROBE’S WORLD
The human microbiome has been a hot topic in biology for the last two decades, and rightly so: Microorganisms that live inside our bodies are so influential that we may ask ourselves if we are more microbial than human after all.
Most of us grow up thinking of microbes as pathogens, and pathogens only. They threaten our health and must be avoided. But it turns out that we humans are gigantic ecosystems of microbes ourselves! More and more research is being conducted on the human microbiota — the microbe populations that we host in and on our bodies. The microbiome, although often used interchangeably with ‘microbiota’, more specifically refers to the totality of the genes that belongs to the microbiota.
The idea of microbes living in human bodies has existed since the mid-1880s. However, the biggest leap for the human microbiome studies started in 2008 with the launch of the Human Microbiome Project that is still going on.
We now know that we have ten times more microbial cells than human cells, and they are essential for our basic functioning. The microbial genes have an immense influence on our metabolism. In fact, there are more microbial protein-coding genes than our own, meaning most of our proteins are of microbial origin: The human genome hosts about 22,000 protein-coding genes while our microbiome has as many as 8,000,000.
Our microbiome is mostly bacterial; but there are also fungi, protozoans, even viruses — and they are everywhere! From our skin to our intestines, from our vagina to our nose, we are surrounded by microbes.
Not only abundant and ubiquitous, but microorganisms that inhabit our tissues are surprisingly diverse too. It is estimated that around 10,000 species may exist in total. The composition of the microbiome varies between individuals and human populations as well as between parts of the body in the same individual. Neither is the composition stable throughout our lives: During birth we get those species from the vaginal microbiota of our mother. If born with a Caesarean section, babies acquire their first microorganisms from the mother’s skin and the environment. During lactation however, our microbiome already starts changing. And with time, depending on our environment, diet, and use of antibiotics, we keep altering its composition.
The microbiome composition in turn, regulates how our digestive, immune, and nervous systems work. Most recent studies are even exploring how it affects our behaviour, mood and mental health. In other words, we are not only what we eat, but also which vagina we came out from, what we touched, and which drugs we used.
