The microbiome’s impact on D. melanogaster reproduction

The microbiome, the aggregate of all microbes that reside in an organism, plays a major role in the metabolism, immunity and overall health of the host¹. Differences in microbial composition can have significant effects on reproductive development and fitness². However, the pathways through which microbes impact host reproductive development are largely unknown. Here, I present findings showing that the microbiome impacts reproduction by modulating mitochondrial activity in the ovarioles of flies. Axenic D. melanogaster were inoculated with microbes donated by two different populations of wild drosophila, generating two experimental populations with different microbiome profiles and reproductive abilities. The ovaries from each population were dissected and stained with a fluorescent mitochondrial marker (Mitotracker) and Tetramethylrhodamine, ethyl ester (TMRE), a dye for mitochondrial potential. Ovariole and mature egg numbers were also counted. Quantitative fluorescent analysis by confocal microscopy revealed that the experimental population of flies exhibiting enhanced fecundity had significantly greater mitochondrial membrane potential and more ovarioles and mature eggs compared to the population of flies with poor fecundity. By contrast, axenic counterparts to each experimental population showed no difference in mitochondrial membrane potential. The findings reveal that i) the microbiome impacts reproduction by changing mitochondrial activity and ovary development; and ii) environmental microbes can modulate host reproductive abilities.