First step of odorant detection in the olfactory epithelium and olfactory preferences differ according to the microbiota profile in mice

We have previously provided thefirst evidence that the microbiota modulates the physiology of the olfactoryepithelium using germfree mice. The extent to which changes to the olfactory system depend on the microbiotais still unknown. In the present work, we explored if different microbiota would differentially impact olfaction.We therefore studied the olfactory function of three groups of mice of the same genetic background, whoseparents had been conventionalized before mating with microbiota from three different mouse strains. Caecalshort chain fatty acids profiles and 16S rRNA gene sequencing ascertained that gut microbiota differed betweenthe three groups. We then used a behavioural test to measure the attractiveness of various odorants and observedthat the three groups of mice differed in their attraction towards odorants. Their olfactory epithelium properties,including electrophysiological responses recorded by electro-olfactograms and expression of genes related to theolfactory transduction pathway, also showed several differences. Overall, our data demonstrate that differencesin gut microbiota profiles are associated with differences in olfactory preferences and in olfactory epitheliumfunctionin