Microbial control over host diet selection

Abstract

AbstractDiet selection is a fundamental aspect of animal behavior with numerous ecological and evolutionary implications1. While the underlying mechanisms are complex, the availability of essential dietary nutrients can strongly influence diet selection2. The gut microbiome has been shown to metabolize many of these same nutrients3, leading to the untested hypothesis that intestinal microbiota may influence diet selection4,5. Here we show that germ-free mice colonized by gut microbiota from three rodent species with distinct foraging strategies differentially selected diets that varied in macronutrient composition. Specifically, we found that herbivore-conventionalized mice voluntarily selected a higher protein:carbohydrate ratio diet, while omnivore- and carnivore-conventionalized mice selected a lower P:C ratio diet. In support of the long-standing hypothesis that tryptophan – the essential amino acid precursor of serotonin – serves as a peripheral signal regulating diet selection6, bacterial genes involved in tryptophan metabolism and plasma tryptophan availability prior to the selection trial were significantly correlated with subsequent voluntary carbohydrate intake. Finally, herbivore-conventionalized mice exhibited larger intestinal compartments associated with microbial fermentation, broadly reflecting the intestinal morphology of their donor species. Together, these results demonstrate that gut microbiome can influence host diet selection and intestinal physiology by mediating the availability of essential amino acids, thereby revealing a novel mechanism by which the gut microbiota influence host foraging behavior.