Abstract
The impact of commensal bacteria on the host arises from complex microbial-diet-host interactions. Mapping metabolic interactions in gut microbial communities is therefore key to understand how the microbiome influences the host. Here we use an interdisciplinary approach including isotope-resolved metabolomics to show that in Drosophila melanogaster, Acetobacter pomorum (Ap) and Lactobacillus plantarum (Lp) a syntrophic relationship is established to overcome detrimental host diets and identify Ap as the bacterium altering the host’s feeding decisions. Specifically, we show that Ap uses the lactate produced by Lp to supply amino acids that are essential to Lp, allowing it to grow in imbalanced diets. Lactate is also necessary and sufficient for Ap to alter the fly’s protein appetite. Our data show that gut bacterial communities use metabolic interactions to become resilient to detrimental host diets. These interactions also ensure the constant flow of metabolites used by the microbiome to alter reproduction and host behaviour.
Highlights
The impact of commensal bacteria on the host arises from complex microbial-diet-host interactions
We show that a syntrophic relationship between Acetobacter pomorum (Ap) and Lactobacillus plantarum (Lp), two abundant strains making up the fly microbiome, is at the base of their ability to suppress yeast appetite in flies deprived of essential amino acids (eAAs)
The presence of any of these bacteria alone cannot suppress protein appetite[8]. These results clearly show that the impact of the microbiome on feeding decisions relies on the presence of a minimal bacterial community consisting of only two members
Summary
The impact of commensal bacteria on the host arises from complex microbial-diet-host interactions. To identify the mechanisms by which bacterial communities act on the host, we will need to map out the relevant interactions among gut microbes influencing the host and identify the molecular and metabolic mechanisms by which they do so This remains a daunting task given the large number of microbial species constituting vertebrate gut microbiomes. The microbiome composition changes rapidly in response to new food choices, such as shifting from plant-based to animal-based diets[34,35,37] or changes in the protein to carbohydrate intake ratio[38] Adding to this complexity, in humans the impact of diet on the microbiome is highly personalised[35]. Given the large number of nutrients required by the host and the nutritional complexity of natural foods, identifying how single nutrients affect the microbiome and the host, remains a key challenge in current microbiome research
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