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Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 7, 2015; 21(29): 8787-8803
Published online Aug 7, 2015. doi: 10.3748/wjg.v21.i29.8787
Role of the normal gut microbiota
Sai Manasa Jandhyala, Rupjyoti Talukdar, Chivkula Subramanyam, Harish Vuyyuru, Mitnala Sasikala, D Nageshwar Reddy
Sai Manasa Jandhyala, Rupjyoti Talukdar, Chivkula Subramanyam, Harish Vuyyuru, Mitnala Sasikala, Department of Gastroenterology, Asian Institute of Gastroenterology, Asian Healthcare Foundation, Hyderabad 500082, India
Rupjyoti Talukdar, D Nageshwar Reddy, Asian Institute of Gastroenterology, Hyderabad 500082, India
Author contributions: Jandhyala SM reviewed the literature and drafted the manuscript; Talukdar R conceived, drafted, reviewed the manuscript and provided intellectual inputs; Vuyyuru H reviewed the literature and drafted the manuscript; Subramanyam C drafted the manuscript and provided intellectual inputs; Sasikala M drafted the manuscript and provided intellectual inputs; and Reddy DN reviewed the manuscript and provided intellectual inputs.
Conflict-of-interest statement: The authors declare no conflicts of interest.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Dr. Rupjyoti Talukdar, Department of Gastroenterology, Asian Institute of Gastroenterology, Asian Healthcare Foundation, 6-3-661 Somajiguda, Hyderabad 500082, India. rup_talukdar@yahoo.com
Telephone: +91-40-23378888 Fax: +91-40-23324255
Received: November 15, 2014
Peer-review started: November 17, 2014
First decision: March 26, 2015
Revised: May 10, 2015
Accepted: July 3, 2015
Article in press: July 3, 2015
Published online: August 7, 2015
Abstract

Relation between the gut microbiota and human health is being increasingly recognised. It is now well established that a healthy gut flora is largely responsible for overall health of the host. The normal human gut microbiota comprises of two major phyla, namely Bacteroidetes and Firmicutes. Though the gut microbiota in an infant appears haphazard, it starts resembling the adult flora by the age of 3 years. Nevertheless, there exist temporal and spatial variations in the microbial distribution from esophagus to the rectum all along the individual’s life span. Developments in genome sequencing technologies and bioinformatics have now enabled scientists to study these microorganisms and their function and microbe-host interactions in an elaborate manner both in health and disease. The normal gut microbiota imparts specific function in host nutrient metabolism, xenobiotic and drug metabolism, maintenance of structural integrity of the gut mucosal barrier, immunomodulation, and protection against pathogens. Several factors play a role in shaping the normal gut microbiota. They include (1) the mode of delivery (vaginal or caesarean); (2) diet during infancy (breast milk or formula feeds) and adulthood (vegan based or meat based); and (3) use of antibiotics or antibiotic like molecules that are derived from the environment or the gut commensal community. A major concern of antibiotic use is the long-term alteration of the normal healthy gut microbiota and horizontal transfer of resistance genes that could result in reservoir of organisms with a multidrug resistant gene pool.

Keywords: Normal gut microbiota, Bioinformatics, Health, Immunomodulation, Metabolic function

Core tip: In this review we present an up-to-date overview of the normal gut microbiota, their functional implications in health, and the mechanistic insights that orchestrate these functions. We also discuss the characteristics that define a healthy gut microbiota and factors that shape and perturb the gut microbial diversity and functions. The evidence that we present here is a composite of observational and experimental studies on humans, germ free and humanized mice.