A critical requirement for research using model organisms is an appropriate, well-defined and consistent diet. There is currently no complete chemically defined (holidic) diet available for Drosophila melanogaster. We describe a holidic medium that is equal in performance to an oligidic diet optimized for adult fecundity and lifespan. It is also sufficient to support development over multiple generations, but at a reduced rate. During seven years of experiments, the holidic diet yielded more consistent experimental outcomes than oligidic food for adult fitness traits. Furthermore, nutrients and drugs are more accessible to flies in holidic medium and, similar to dietary restriction on oligidic food, amino acid dilution increases fly lifespan. We also report amino acid specific effects on food choice behavior and that folic acid from the microbiota is sufficient for development. These insights could not be gained using oligidic or meridic diets.

Choosing the right nutrients to consume is essential to health and wellbeing across species. However, the factors that influence these decisions are poorly understood. This is particularly true for dietary proteins, which are important determinants of lifespan and reproduction. We show that in Drosophila melanogaster, essential amino acids (eAAs) and the concerted action of the commensal bacteria Acetobacter pomorum and Lactobacilli are critical modulators of food choice. Using a chemically defined diet, we show that the absence of any single eAA from the diet is sufficient to elicit specific appetites for amino acid (AA)-rich food. Furthermore, commensal bacteria buffer the animal from the lack of dietary eAAs: both increased yeast appetite and decreased reproduction induced by eAA deprivation are rescued by the presence of commensals. Surprisingly, these effects do not seem to be due to changes in AA titers, suggesting that gut bacteria act through a different mechanism to change behavior and reproduction. Thus, eAAs and commensal bacteria are potent modulators of feeding decisions and reproductive output. This demonstrates how the interaction of specific nutrients with the microbiome can shape behavioral decisions and life history traits.

Dominant-intermediate Charcot-Marie-Tooth neuropathy (DI-CMT