Kraimi, N. et al. J. Exp. Biol. jeb.202879 (2019)

Several studies have started to link alterations in the gut microbiota (GM)-brain axis to gastrointestinal and neurological diseases. A study now suggests that the gut-brain axis also influences emotional reactivity. Germ-free chicks from a Japanese quail line (Coturnix japonica) selected for a high emotional reactivity (E + ) that had been colonized with GM from a line with low emotional reactivity (E-) showed reduced emotional behaviour compared with germ-free chicks from E + line colonized with GM from the E + line. Results were reversed when behaviour was tested at a later stage, most likely owing to the resilience of GM to recover its equilibrium present in the E + host. This study shows that GM transfer can influence emotional reactivity in Japanese quails and supports the existence of a GM-brain axis in birds.