The close association between deregulated intestinal microbial consortia and host diseases such as chronic inflammation has been recognized since the birth of microbiology over a century ago.These phenomena are collectively called intestinal dysbiosis.However,many important questions remain unanswered because it is still obscure whether deregulation of the gut microbiota community is the consequence or cause of the chronic inflammation.Recent studies using Drosophila and its simple microbiota have provided a valuable model system for dissecting the molecular mechanisms of intestinal dysbiosis.In this talk,I will present basic aspects of gut-microbe interactions in metazoan,as well as recent exciting observations obtained from Drosophila gut-microbiota model system,particularly the interaction between host immunity and different microbiota.Future genetic screening using Drosophila model system will provide key molecules and mechanisms governing gut-microbe symbiosis and dysbiosis.