A naturally isolated symbiotic bacterium suppresses flavivirus transmission by mosquitoes.

The commensal microbiota of the mosquito gut plays a complex role in determining the vector competence for arboviruses. In this study, we identified a bacterium from the gut of field mosquitoes named sp. YN46 (YN46) that rendered mosquitoes refractory to infection with dengue and Zika viruses. Inoculation of 1.6 × 10 colony forming units (CFUs) of YN46 into mosquitoes effectively prevents viral infection. Mechanistically, this bacterium secretes glucose dehydrogenase (GDH), which acidifies the gut lumen of fed mosquitoes, causing irreversible conformational changes in the flavivirus envelope protein that prevent viral entry into cells. In semifield conditions, YN46 exhibits effective transstadial transmission in field mosquitoes, which blocks transmission of dengue virus by newly emerged adult mosquitoes. The prevalence of YN46 is greater in mosquitoes from low-dengue areas (52.9 to ~91.7%) than in those from dengue-endemic regions (0 to ~6.7%). YN46 may offer an effective and safe lead for flavivirus biocontrol.