Effects of gut microbiota manipulation on memory in Drosophila melanogaster

The gut and brain interact in a bidirectional relationship known as the gut-brain axis, and the chemical communication provided by the bacteria of the gut may facilitate this interaction. In this thesis, I first reviewed the literature on the different factors that might affect learning and memory in insects, showing that only few studies explored the effects of the gut microbiota manipulation on these traits. Then, using Drosophila melanogaster as a model, I investigated whether manipulation of the gut bacterial composition could be associated with alterations in memory performance. I also explored if these changes can be recovered following the colonization of Drosophila with two core gut commensals, Acetobacter pomorum and Lactobacillus plantarum. Our data indicated that germ-free flies experienced a strong reduction in memory performance compared to conventional flies, confirming that alteration of the gut bacteria negatively affects memory performance in vinegar flies. Furthermore, when flies were re-inoculated with core gut bacteria, they partially recovered their memory. Further investigations are needed to unravel the underlying mechanisms through which the gut bacteria can alter the cognition of the host.