Intra-specific diversity of Serratia marcescens in Anopheles mosquito midgut defines Plasmodium transmission capacity

A critical stage in malaria transmission occurs in the Anophelesmosquito midgut, when the malaria parasite, Plasmodium, ingested with blood, first makes contact with the gut epithelial surface. To understand the response mechanisms within the midgut environment, including those influenced by resident microbiota againstPlasmodium, we focus on a midgut bacteria species' intra-specific variation that confers diversity to the mosquito's competency for malaria transmission.Serratiamarcescensisolated from either laboratory-reared mosquitoes or wild populations in Burkina Faso shows great phenotypic variation in its cellular and structural features. Importantly, this variation is directly correlated with its ability to inhibit Plasmodiumdevelopment within the mosquito midgut. Furthermore, this anti-Plasmodium function conferred by Serratia marcescensrequires increased expression of the flagellum biosynthetic pathway that is modulated by the motility master regulatory operon, flhDC. These findings point to new strategies for controlling malaria through genetic manipulation of midgut bacteria within the mosquito.