What Is the Human Microbiome, Exactly?

The human body is made up of trillions of human cells. There are possibly three times as many microorganisms (bacteria, fungi, and other microbes) living in and on the human body. The microbial communities in and on the human body are known as the human microbiome.

The microbiome contributes considerably to human growth, development, and function. The most well known is the gut microbiome, which impacts human digestive health.

Metaphors that scientists use to talk about the microbiome influence scientific understanding and can shape medical treatment. For example, viewing the microbiome as an "organ" or a "part of the immune system."

Some physicians support fecal microbiota transplantation (FMT) - treating the malfunction of the gut microbiome by swallowing a pill full of someone else's poo. It follows the same basic principles as an organ transplant, and the treatment is probably a consequence of understanding the microbiome as an organ.