Wolbachia is a nutritional symbiont in Drosophila melanogaster

The intracellular bacterium Wolbachia is a common symbiont of many arthropods and nematodes, well studied for its impacts on host reproductive biology. However, its broad success as a vertically transmitted infection cannot be attributed to manipulations of host reproduction alone. Using the Drosophila melanogaster model and their natively associated Wolbachia strain “wMel”, we show that Wolbachia infection supports fly development and buffers against nutritional stress. Wolbachia infection across several fly genotypes and a range of nutrient conditions resulted in reduced pupal mortality, increased adult emergence, and larger size. We determined that the exogenous supplementation of pyrimidines rescued these phenotypes in the Wolbachia-free, flies suggesting that Wolbachia plays a role in providing this metabolite that is normally limiting for fly growth. Additionally, Wolbachia was sensitive to host pyrimidine metabolism: Wolbachia titers increased upon transgenic knockdown of the Drosophila de novo pyrimidine synthesis pathway but not knockdown of the de novo purine synthesis pathway. We propose that Wolbachia acts as a nutritional symbiont to supplement fly development and enhance host fitness.