Substances that are not cells that make up the human body
Half of the human body is made up of a substance called the human microbiome.
Cellular tissue is not the only component of the human body.
It also contains a lot of bacteria and fungi.
These non-cellular substances are collectively called the ”human microbiome.”
The microbiome is present throughout the body.
The “gut flora,” a collection of intestinal bacteria, is a particularly frequent topic.
In the human intestine, various chemical substances are produced by the action of the gut flora.
Hormones called “intracerebral drugs” can be made by gut flora.
For example, when the hormone “serotonin” is secreted, you feel happy.
Serotonin is produced by the gut flora.
In other words, it is no exaggeration to say that fungi make us happy.
– University of Washington: The Human Microbiome