Visualization of endogenous gut bacteria in Drosophila melanogaster using fluorescence in situ hybridization.

All metazoans are colonized by a complex and diverse set of microorganisms. The microbes colonize all parts of the body and are especially abundant in the gastrointestinal tract, where they constitute the gut microbiome. The fruit fly Drosophila melanogaster turned out to be an exquisite model organism to functionally test the importance of an intact gut microbiome. Still, however, fundamental questions remain unanswered. For example, it is unknown whether a fine-tuned regionalization of the gut microbiome exists and how such a spatial organization could be established. In order to pave the way for answering this question, we generated an optimized and adapted fluorescence in situ hybridization (FISH) protocol. We focused on the detection of the two major Drosophila gut microbiome constituting bacteria genera: Acetobacter and Lactobacillus. FISH allows to detect the bacteria in situ and thus to investigate their spatial localization in respect to the host as well as to other microbiome members. We demonstrate the applicability of the protocol using a diverse set of sample types.