Alexandre, 10 years old: “What is a good microbe? »

• The human body “contains” very few pathogenic microbes (that is to say that make you sick for sure), according to our partner The Conversation.

• Many microbes are even necessary to us because they help our body to react and fight against other "bad" microbes.

• This analysis was conducted by Marc GJ Feuilloley, professor of microbiology.

Have you ever wondered if you were good or bad, or just nice or bad?

You could say a little of both, depending on the moment (although I'm sure you're mostly very nice).

Well, for "germs" it's a bit the same thing.

First you have to know what you are talking about.

Under this name of microbe, we group together a whole number of organisms that we cannot see with the naked eye, they are said to be microscopic, including bacteria, yeasts, fungi and even viruses.

In the human body, these microorganisms are grouped under the term microbiota and in an adult this represents a mass of 1.5 to 2 kg, it is more than the weight of our brain.

This microbiota is mainly located in the intestine, but there are also many microbes on the skin, on the eyes, in the mouth, nose, lungs and even the bladder.

We thought for a long time that the best thing to do with these micro-organisms was to eliminate them, but we now know that this would be a serious mistake.

First we must remember that in reality, there are very few microbes that make you sick for sure, they are called pathogens.

Most are called opportunistic pathogens, that is to say they are not able to infect us all the time.

It varies depending on where they grow, much like a weed that is only bad because it doesn't grow where we want it to grow, or because molecules (chemicals) produced by our own bodies stress and make them aggressive.

We can even carry pathogenic microbes in or on our bodies without ever getting sick.

It all depends on whether they are active or not and how many there are.

In fact, many microbes are even necessary for us.

First, they occupy places which, if they were not there, could be used by pathogenic microbes.

Then they help our body to react and fight against other microbes.

On the other hand, these microbes, which in a certain way are part of ourselves and are sometimes considered as an organ in their own right, produce molecules which are essential to us such as vitamins or bile acids necessary for digestion.

In the end, without our microbiota we would be very sick.

But the most amazing thing is that we have discovered that microbes communicate with the cells of our body, and that in both directions.

Our cells are able to detect microbes on and in our body.

This is necessary for the renewal of the cells of our intestine and our skin and also serves to train our immune system which defends us against external aggressions.

Intestinal microbes would even be able to produce molecules that pass into our blood and act on our brain and regulate our hunger and weight gain.

But the most amazing thing is that microbes are also able to detect the signals that our cells produce.

In this way, microbes are able to sense our state of stress.

For example, we know that acne pimples often develop when we are stressed and we have seen that bacteria in the skin can sense the molecules released by our body when we are stressed and promote the formation of these pimples.

So, good or bad microbe, in reality everything depends on the number, the place and the environment.

I won't tell you not to wash, but you should avoid showering with too aggressive gels and rubbing your skin hard.

Our “<strong> DISEASES </strong>” file

It's the same for the intestine, if antibiotics kill part of our microbiota, it goes wrong and it's better not to go far from the WC.

In most cases we get along very well with our microbiota, it is part of us and as with all living beings, it must be preserved.

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This analysis was written by Marc GJ Feuilloley, professor of microbiology at the University of Rouen Normandy.

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• Science

• Video

• The Conversation

• Bacterium

• Biology

• Sickness