The intracellular symbiont Wolbachia alters Drosophila development and metabolism to buffer against nutritional stress

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 natively associated Wolbachia strain "wMel", we show that Wolbachia infection supports fly development and buffers against nutritional stress. Wolbachia infection across two fly genotypes and a range of nutrient conditions resulted in reduced pupal mortality, increased adult emergence, and larger size. In parallel, transcriptomic and metabolomic analyses indicated that Wolbachia impacts a wide range of developmental and metabolic processes. Wolbachia-infected larvae had strong signatures of shifts in glutathione and mitochondrial metabolism, plus significant changes in the expression of key developmental regulators including Notch, the insulin receptor (lnR), and the juvenile hormone receptor Methoprene-tolerant (Met). We propose that Wolbachia can enhance host fitness by supporting fly development, especially during periods of nutrient stress.