Gut bacteria mediate nutrient availabilityin Drosophiladiets

Summary Drosophila melanogaster gut microbes play important roles in host nutritional physiology. However, these associations are often indirect and studies typically are in the context of specialized nutritional conditions, making it difficult to discern how microbiome-mediated impacts translate to physiologically relevant conditions, in the laboratory or nature. Here, we show that on three artificial diets and a natural diet of grapes, D. melanogaster gut bacteria alter protein, carbohydrates, and moisture of the food substrate. In depth analysis on one diet revealed bacteria also increase tryptophan levels. We investigate how nutrient changes impact life history and find that, while alterations to dietary protein and carbohydrates are arguably the most significant consequence of bacterial association, other factors, such as micronutrients, likely contribute to life history traits in a diet-dependent manner. Our work demonstrates that while some bacterial impacts on nutrition occur across experimental diets, others are dictated by unique dietary environments.