Transcriptomics of gnotobiotic and axenic larval Aedes aegypti reveal effects of gut community on development and homeostasis

Bacteria play an essential role in mosquito larval development: axenic larvae lacking bacteria fail to develop beyond the first instar and subsequently die. We sought to explore the effects of bacteria on the mosquito midgut using a transcriptomics approach. Gnotobiotic mosquito larvae were produced by providing sterile larvae with E. coli and comparing the transcriptome of the mosquito gut to the remaining carcass. Midgut- and carcass-specific transcriptomes were also produced using axenic larvae. These datasets revealed that several families of mosquito genes are differentially regulated in the absence of bacteria. These families included immune genes in the IMD/Toll pathway, several metabolic regulators, and structural proteins. Together, these results suggest that microbes have profound effects on the physiology of the larval mosquito midgut and provide insights into the mechanisms by which they influence development.