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Résumé Le microbiote intestinal humain est composé de 10 14 bactéries ainsi que d’autres micro-organismes comme les virus, les champignons et les archées. L’étude du microbiote intestinal a dévoilé le rôle fondamental qu’il joue dans la physiologie intestinale mais aussi dans la santé humaine de façon plus générale, comme un véritable« organe caché ». Dans cette revue, nous exposons la structure et le rôle du microbiote intestinal ainsi que son implication en pathologie humaine. Après la colonisation bactérienne du tube digestif chez le nourrisson, la composition du microbiote intestinal est unique à chaque individu bien que plus de 95 % des bactéries le composant puissent être réparties en 4 phyla majeurs. Des approches culture-indépendantes et, plus récemment, l’avènement du séquençage haut débit ont permis de décrire précisément la structure et la diversité du microbiote intestinal ainsi que son altération en pathologie. Le microbiote intestinal est impliqué dans la maturation du système immunitaire et dans de nombreuses voies métaboliques fondamentales comme la fermentation des sucres et des protéines ainsi que le métabolisme des acides biliaires et des xénobiotiques. Le déséquilibre des populations du microbiote intestinal ou dysbiose a des conséquences fonctionnelles importantes et est impliqué dans de nombreuses pathologies digestives (maladies inflammatoires chroniques intestinales, cancer colorectal, etc.) mais aussi dans l’obésité et l’autisme. Ces observations ont conduit à l’émergence de nombreuses études sur les traitements visant à restaurer l’équilibre du microbiote intestinal comme les probiotiques ou la transplantation du microbiote fécal. Mais des travaux récents sur l’activité de métabolites issus du microbiote pourraient conduire à des perspectives thérapeutiques prometteuses. The human gut contains 10 14 bacteria and many other micro-organisms such as Archaea, viruses and fungi. Studying the gut microbiota showed how this entity participates to gut physiology and beyond this to human health, as a real “hidden organ”. In this review, we aimed to bring information about gut microbiota, its structure, its roles and its implication in human pathology. After bacterial colonization in infant, intestinal microbial composition is unique for each individual although more than 95% can be assigned to four major phyla. The use of culture independent methods and more recently the development of high throughput sequencing allowed to depict precisely gut microbiota structure and diversity as well as its alteration in diseases. Gut microbiota is implicated in the maturation of the host immune system and in many fundamental metabolic pathways including sugars and proteins fermentation and metabolism of bile acids and xenobiotics. Imbalance of gut microbial populations or dysbiosis has important functional consequences and is implicated in many digestive diseases (inflammatory bowel diseases, colorectal cancer, etc.) but also in obesity and autism. These observations have led to a surge of studies exploring therapeutics which aims to restore gut microbiota equilibrium such as probiotics or fecal microbiota transplantation. But recent research also investigates biological activity of microbial products which could lead to interesting therapeutics leads. [ABSTRACT FROM AUTHOR]

The human gut contains 10(14) bacteria and many other micro-organisms such as Archaea, viruses and fungi. Studying the gut microbiota showed how this entity participates to gut physiology and beyond this to human health, as a real "hidden organ". In this review, we aimed to bring information about gut microbiota, its structure, its roles and its implication in human pathology. After bacterial colonization in infant, intestinal microbial composition is unique for each individual although more than 95% can be assigned to four major phyla. The use of culture independent methods and more recently the development of high throughput sequencing allowed to depict precisely gut microbiota structure and diversity as well as its alteration in diseases. Gut microbiota is implicated in the maturation of the host immune system and in many fundamental metabolic pathways including sugars and proteins fermentation and metabolism of bile acids and xenobiotics. Imbalance of gut microbial populations or dysbiosis has important functional consequences and is implicated in many digestive diseases (inflammatory bowel diseases, colorectal cancer, etc.) but also in obesity and autism. These observations have led to a surge of studies exploring therapeutics which aims to restore gut microbiota equilibrium such as probiotics or fecal microbiota transplantation. But recent research also investigates biological activity of microbial products which could lead to interesting therapeutics leads., (Copyright © 2015 Société Nationale Française de Médecine Interne (SNFMI). Published by Elsevier SAS. All rights reserved.)

The intestinal microbiota is known to be composed by several hundred different bacterial species and is stable over time. Antibiotics intake induces a disturbance in the composition of intestinal microbiota which impairs its protective role against infection by pathogens. The presence of a large biomass of bacteria in the digestive tract exerts physiological effects with beneficial consequences for the host. Patients with inflammatory bowel diseases, exhibit an imbalance in the composition of intestinal microbiota called dysbiosis., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)