It is not surprising than an adult human body contains hundred trillion bacteria. The composite microbial genome found in the mammalian gastrointestinal tract is termed as gut microbiome. Various metagenomic studies have tried to dissect out the distribution of microbiota in gut and the diversity of microbiome functionally related to the health conditions. Also these microbiomes are risk factors for illness such as asthma, inflammatory bowel disease and metabolic disorders. Human health is regulated by gut microbiome in many different ways, such as direct stimulation of afferent neurons of the enteric nervous system via vagus nerve to central nervous system inflammation, protection against infection, generation of innate memory and functional reprogramming of bone marrow progenitors. In this review article, authors discussed how the varying composition of gut microbiota at different situations related
directly or indirectly to human health.

Keyword: Gut microbiota; Bioreactor; Gastrointestinal tract (GI tract); Innate immunity.