An altered microbiome in a Parkinson's disease model Drosophila melanogaster has a negative effect on development

Parkinson's disease (PD) is the second most common neurodegenerative disease, besides Alzheimer's Disease, characterized by multiple symptoms, including the well-known motor dysfunctions. It is well-established that there are differences in the fecal microbiota composition between Parkinson's disease (PD) patients and control populations, but the mechanisms underlying these differences are not yet fully understood. To begin to close the gap between description and mechanism we studied the relationship between the microbiota and PD in a model organism, Drosophila melanogaster. First, fecal transfers were performed with a D. melanogaster model of PD that had a mutation in the parkin (park²⁵) gene. Results indicate that the PD model feces had a negative effect on both pupation and eclosion in both control and park²⁵ flies, with a greater effect in PD model flies. Analysis of the microbiota composition revealed differences between the control and park²⁵ flies, consistent with many human studies. Conversely, gnotobiotic treatment of axenic embryos with feces-derived bacterial cultures did not affect eclosure. We speculate this result might be due to similarities in bacterial prevalence between mutant and control feces. Further, we confirmed a bacteria-potentiated impact on mutant and control fly phenotypes by measuring eclosure rate in park²⁵ flies that were mono-associated with members of the fly microbiota. Both the fecal transfer and the mono-association results indicate a host genotype-microbiota interaction. Overall, this study concludes functional effects of the fly microbiota on PD model flies, providing support to the developing body of knowledge regarding the influence of the microbiota on PD.