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Abstract

The digestive tract is the first organ in contact with the bacteria ingested along with food. While commensal bacteria become resident, opportunistic or virulent bacteria are rapidly eliminated from the gut. Using the host-pathogen interaction between Drosophila melanogaster and Bacillus thuringiensis, we characterized a new mechanism of defense corresponding to a huge visceral contraction (we named pathological contraction) required to help to eliminate the ingested vegetative bacteria. We showed that this visceral contraction is induced by the presence of the immune ROS in the lumen and is relayed by the enteroendocrine cells that secrete the DH31 neuropeptide. Consequently in less than 1 hour post-ingestion, the visceral muscle strongly contracts favoring vegetative bacteria expelling. Finally, we showed that Bacillus thuringiensis spores (used as bioinscticide) persist for a longer time in the intestine because they are not detected by the local innate immune system of the anterior midgut.