The gut commensal microbiome of Drosophila is modified by the endosymbiont Wolbachia
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Citation (published version)Rama Simhadri, Eva Fast, Guo Rong, Michaela Schultz, Natalie Vaisman, Ortiz Luis, Joana Bybee, Barton Slatko, Horacio Frydman. 2017. "The gut commensal microbiome of Drosophila is modified by the endosymbiont Wolbachia." mSphere, Volume 2, Issue 5, https://doi.org/10.1128/mSphere.00287-17
Endosymbiotic Wolbachia bacteria and the gut microbiome have inde- pendently been shown to affect several aspects of insect biology, including repro- duction, development, life span, stem cell activity, and resistance to human patho- gens, in insect vectors. This work shows that Wolbachia bacteria, which reside mainly in the fly germline, affect the microbial species present in the fly gut in a lab-reared strain. Drosophila melanogaster hosts two main genera of commensal bac- teria—Acetobacter and Lactobacillus. Wolbachia-infected flies have significantly re- duced titers of Acetobacter. Sampling of the microbiome of axenic flies fed with equal proportions of both bacteria shows that the presence of Wolbachia bacteria is a significant determinant of the composition of the microbiome throughout fly de- velopment. However, this effect is host genotype dependent. To investigate the mechanism of microbiome modulation, the effect of Wolbachia bacteria on Imd and reactive oxygen species pathways, the main regulators of immune response in the fly gut, was measured. The presence of Wolbachia bacteria does not induce signifi- cant changes in the expression of the genes for the effector molecules in either pathway. Furthermore, microbiome modulation is not due to direct interaction be- tween Wolbachia bacteria and gut microbes. Confocal analysis shows that Wolbachia bacteria are absent from the gut lumen. These results indicate that the mechanistic basis of the modulation of composition of the microbiome by Wolbachia bacteria is more complex than a direct bacterial interaction or the effect of Wolbachia bacteria on fly immunity. The findings reported here highlight the importance of considering the composition of the gut microbiome and host genetic background during Wolbachia-induced phenotypic studies and when formulating microbe-based disease vector control strategies.
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