[Definition and roles of the gut microbiota]
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Updated: Sep 23, 2026

Applying Advanced In Vitro Culturing Technology to Study the Human Gut Microbiota
Published on: February 15, 2019
1Service de Gastroenterologie, Hopital St Antoine, AP-HP, Paris, France. Centre de recherche Saint-Antoine, (CRSA, UMRS 938), Inserm, Sorbonne Université, Paris, France. INRA, UMR1319, Micalis, Jouy-en- Josas, France.
Abstract:
Definition and roles of the gut microbiota. The gut microbiota is the set of microorganisms that colonize our digestive tract. A human being hosts 1013 bacteria in his gastro-intestinal tract, as much as human cells in his body. The microbiota contains bacteria but also fungi, viruses and protists. The microbiota settles gradually after birth is considered adult around the age of 3 years. The microbiota can be modulated by many environmental factors and by the genetics of the host. An unbalanced microbiota (dysbiotic) is observed in many human diseases and plays a role in many of them, with however unequal weight from one disease to another. The microbiota could, in the near future, serve as a diagnostic and prognostic biomarker. It is already considered a potential therapeutic tool or target.
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