The Microbiome – Hidden Habitat Inside Us
An average adult human is made up of around 30 trillion body cells. 30,000,000,000,000 - that's quite a lot when written out as a number. This gigantic cluster of cells in turn provides food and lodging for around 39 trillion guests, microorganisms that have made humans their habitat. Some live on us, on our skin, but most live inside us, especially in our digestive system. What may sound frightening at first turns out to be a fascinating partnership on closer inspection. Because it is the small life, the microbiome, without which our big life would not be possible.
The young woman knows that the intestines are important for her health.
Microbiome – What is it?
In its original sense, the term microbiome refers to the totality of all microorganisms living on earth. In common parlance, the term usually refers to the organisms that colonize humans, but above all the intestinal inhabitants or the intestinal microbiome. Countless probiotic products in advertising have probably contributed a lot to the popularity of intestinal flora. However, the term intestinal flora is not entirely correct. It comes from a time when bacteria and fungi, which make up the intestinal microbiome, were still classified as part of the plant kingdom. Today, these microorganisms are each considered to be a separate kingdom. More than 10,000 different bacteria and fungi are known to colonize on and in humans. Each person has a very individual microbiome, which is made up of 500 to 1,000 species. Some species live on humans as so-called commensals, i.e. simply as beneficiaries. With other organisms, a complex interaction has developed over the course of evolution, so that humans and microorganisms are dependent on one another. The functions of the intestinal microbiome are so diverse that some researchers already refer to it as an independent organ.
function of the microbiome
The skin's microbiome benefits humans by acting as a protective shield to fend off harmful microorganisms. This happens because foreign organisms simply have no place to settle. In addition, the metabolic products of the bacteria help to maintain the skin's protective acid mantle. However, most microorganisms colonize the digestive system. The mass of the intestinal microbiome is estimated at a good one and a half kilograms. The microbes crowd closely together against the intestinal mucosa and prevent harmful germs from penetrating here too. The intestinal microbiome also plays a crucial role in human metabolism. Intestinal bacteria have 200 enzymes for breaking down carbohydrates, while humans only have 17 enzymes. They are also involved in the synthesis of vitamins B1, B2, B6, B12 and K. Difficult-to-digest fiber is converted by the intestinal microbiome into valuable, short-chain fatty acids . In addition, the intestinal microbiome is in constant contact with the immune system via the 600 m² intestinal mucosa and provokes a continuous immune response. You could say that the intestinal microbiome is the sparring partner for the immune system. Intestinal bacteria can even produce neurotransmitters and in this way come into contact with the nervous system. It has already been shown in mice that their intestinal microbiome influences their behavior. There are indications that this could also be the case in humans - but this has not yet been proven. However, the complexity of this symbiosis was also underestimated for a long time. Research has only really picked up speed in the last ten years.
Where does the gut microbiome come from?
The foundation for the intestinal flora is passed on from mother to child. Even the type of birth has an influence on the microbiome. During a vaginal birth, the child comes into contact with different germs than during a Caesarean section. The type of diet, how long breast milk is given and when supplementary feeding begins, is also crucial. In the years that follow, other strains of bacteria enter the organism through crawling, playing, putting hands, feet and objects in the mouth. The changed hygienic conditions of modern life have probably led to the fact that the diversity of the microbiome is lower today than it was a hundred years ago. Nevertheless, children aged two to three have an almost complete microbiome, which only changes significantly again in old age, from the age of 80.
What influences the microbiome?
The intestinal microbiome is a complex ecosystem. The microorganisms not only interact with their host, but also maintain mutual relationships with each other. Some bacteria do not directly utilize human food, but the metabolic products of other bacterial strains. However, the decisive influence on the intestinal population is diet. A one-sided diet leads to larger populations of bacterial strains that specialize in these nutrients. Other bacterial strains can be displaced as a result. However, if the diet is changed, the microbiome quickly returns to its original state. Taking medication, especially antibiotics, can have a more drastic effect. As helpful and necessary as antibiotics are for some diseases, they do not differentiate between beneficial and harmful bacteria. Diarrhea is one of the consequences of such a disturbed intestinal microbiome. But in most cases it recovers within a few weeks.
The three basic types of microbiome
The microbiome therefore has a fairly high level of resilience . There are three basic types of intestinal microbiome, depending on which bacterial strains form the largest population in the normal state.
These so-called enterotypes of the intestinal flora are:
- Enterotype 1: Bacteria of the genus Bacteroides dominate. These preferentially break down carbohydrates and provide the vitamins riboflavin, biotin and ascorbic acid.
- Enterotype 2: Prevotella bacteria dominate. Specialized in sugar-protein complexes and produce thiamine and folic acid.
- Enterotype 3: Ruminococcus bacteria dominate. Specialized in the breakdown of the intestinal mucosa. Forms short-chain fatty acids, among other things. Enterotype 3 is the most common type.
All three types ensure the energy supply of their host, to which they are optimally adapted, in their own way. It is not yet clear whether a permanent change in enterotype is possible by changing the diet.
