Characterization of the human gut microbiota has caused a paradigm shift in modern biomedical research. Maintenance of gut microbiota depends on mutual microbe-host interactions, which when disturbed can lead to dysbiosis. Dysbiosis has been associated with a variety of autoimmune and metabolic diseases. Studies attempt to define bacterial compositional changes, immunity responses or molecular patterns associated with specific diseases. The immense research in the human microbiota may lead to novel therapeutic strategies by development of commensal microbe products in management of diseases.