Everyone knows what the brain is, but not everyone knows what the microbiome is. This is the complex of viruses, bacteria and fungi that play a crucial role in our health and cognitive functions. An entire population of collaborators living in our bodies, to put it briefly.
Also known as the microbiota, this 'army' has long been based in the gastrointestinal tract, according to science. We recently learned that it is also found in the skin. Again according to science, for a long time it was believed that several areas of the body lacked it: for example the eye and the womb. Recent diagnostic advances have recently made it possible to identify a microbiome of the placenta and one of the eye, both present in healthy people. At this point it is reasonable to expect other discoveries soon.
Are we certain, for example, that the brain is a sterile, bacteria-free area, or does it have a microbiome? This is the object of the incredible intervention at the conference of the US Society of Neuroscience last November 2018. A research team from the University of Alabama – Birmingham (UAB), led by Dr. Rosalinda Roberts, showed high resolution microscopic images of the brain of mice and humans. These images clearly show bacteria inside astrocytes, the cells that interact with neurons in the brain.
Like so many teams making astonishing discoveries, this one wasn't looking for bacteria in the brain at all. The fact that the brain is a sterile area was recognized throughout the scientific world.
Researcher Courtney Walker was comparing images of the brains of healthy people with those of people suffering from schizophrenia under the microscope, to evaluate any structural differences, when she came across the discovery. After the first surprise, the analysis was extended to all the human brains that the laboratory had under analysis. All 34 had bacteria.
The first investigations
To determine whether their presence was the result of contamination after death, Dr. Roberts and her team studied the brains of mice in life and immediately after death. Surprisingly, bacteria were found there too.
Perhaps the contamination occurred in the preparation of the brain samples to be analyzed? Even analyzes in sterile environments have provided clues in one direction.
The in-depth analysis
The team then used RNA sequencing to identify what type of bacteria were present in the brains of mice and humans. Everyone is Firmicuti, proteobacteria e bacteroides commonly found in the intestine. How did they end up in the brain?
These first, stunning observations have left many questions open: are these bacteria "cooperative" or pathological? Does the quantity and composition of the brain microbiome change over time? Where do these bacteria come from? Questions that will perhaps be answered in connection with the recent discovery of an immune system in the brain. All these changes will lead to the explosion of what is still an emerging scientific field today: psychoneuroimmunology.
It has become as archaic as the beliefs of the 1300s to believe that bacteria are just an enemy to be fought. We have long known that we host entire cities, nations, planets in our bodies: endless populations of organisms that live with us, "work" with us and help us in many cases.
