Advances in DNA-sequencing methods,establishment of germ free,gnotobiotic,mono-bi,selective polyassociated,or human flora-associated animal models facilitated detailed studies to assess the effects of the microbiota on complex organisms under physiological and pathological conditions.Recently,a bidirectional communication axis between brain and the gut microbiota was described and suggested to be an important factor in the development and course of several diseases of the nervous system.