Gut bacteria-derived volatiles mediate Drosophila melanogaster attraction

Bacteria-originated volatile molecules play a crucial role in chemical communications between insects, representing their promising application as odor bait traps in pest control. In this study, we investigated the behavioral preferences of the fruit fly Drosophila melanogaster (Diptera: Drosophilidae) towards the fermentation broth of seven gut-associated bacteria using trap choice assays. All seven bacterial fermentations significantly attracted adults and larvae compared to the medium control. We assessed the effects of bacterial fermentations on bayberry attractiveness to fly adults, and found that the bayberries sprayed with fermentation broth of seven bacteria were all significantly more attractive to adults than the non-sprayed, following in increased total egg numbers. We also compared the attractive effect of bacterial fermentations with a sugar-vinegar mixture and a commercial odor-bait. The commercial odor bait proved more enticing than the unconcentrated 5-day fermentation broths. However, out of the seven bacteria, 64-fold concentrated bacterial fermentation of Corynebacterium (Actinomycetota phylum) was significantly more attractive than commercial bait. Finally, we chemically identified the predominant compounds 2-methylpropanal and acetaldehyde, which are likely responsible for the behavioral preference of fruit flies. Our findings provide a deeper understanding of how gut microbes affect insect behavior and offer a potential bacteria-originated odor bait for fly control in the orchard.