Glossary · Y học
Gut microbiota
The community of microorganisms — chiefly bacteria — living in the human digestive tract. A 2016 re-estimate found that the number of bacterial cells in the human body is roughly the same as the number of the body's own cells, not ten times as many as the older, often-quoted figure.
The human digestive tract is home to a dense community of microorganisms, most abundant in the large intestine.
The figure that is often misquoted is that bacteria outnumber human cells ten to one. Sender, Fuchs and Milo (2016) recalculated this and reached a different estimate: for a reference person, bacterial cells number about 3.8×10¹³ and the body's own cells about 3.0×10¹³, a ratio close to 1:1 rather than 10:1. This is an important numerical correction: the old "ten times" figure had no solid basis.
This microbiota is not passive. Yano et al. (2015) showed that in mice, gut bacteria regulate the biosynthesis of serotonin from enterochromaffin cells — a concrete example of how the microbiota acts on the host's signalling chemistry.