Presence of microbiota reverses the relative performance of Daphnia on two experimental diets.

•The microbiota of the aquatic model crustacean Daphnia magna determines its response to different experimental diets.•Bacteria-free Daphnia grows larger on a diet of yeast.•Conventionalized Daphnia grows larger on a diet of algae.•This suggests that the microbiota enables the host to benefit from the algal diet.