Gut bacteria in fruit flies do not have a major influence on behavior
(PHYSorg.com Biology)

Microbial communities residing within the gut have been implicated in several aspects of health and disease. The mammalian gut microbiome, for example, not only influences metabolic functions and immune responses, but has also been found to affect mood, cognition, pain and anxiety. However, a recent study by Singaporean scientists has shown this is not the case for flies.