LAUSR

Abstract Microbiota refers to an abundant and diverse population of bacteria, archaea, fungi and other microbial eukaryotic species reside in the gastrointestinal tracts and other body sites exposed to the environment. A Microbial symbiosis was established between the host and the microbial flora. The host provides a favorable environment for the colonization of microbiota and in respect to this microbial flora actively participates in the metabolic process of the host, synthesis of vitamins, production of nutrients, enhancement of mucosal barrier functions, and also inhibits the colonization of pathogens. In addition to this Microbial flora have the fundamental role in the development and establishment of host immune homeostasis. Microbiota induces the protective responses against the pathogens and modulates the regulatory pathways in such way to develop the tolerance against the innocuous antigens. Alteration in the composition of microbial flora results in many gastrointestinal diseases including obesity, inflammatory bowel diseases, systemic infections, autoimmune disorders, and even colon cancers. These features of microbiota focus the research on their composition and a wide range of their functional aspects. The objective of this review is to explore the symbiotic relationship between intestinal microbiota and host, the contribution of the microbial flora in host immune homeostasis as well as the concept of ‘probiotics’ as a possible therapeutic approach to restore the normal gut microbial flora and host immune homeostasis.