Exposure toPseudomonas spp.increasesAnopheles gambiaeinsecticide resistance in a population-dependent manner

The microbiota of mosquitoes influences many aspects of their biology, including developmental processes, mating and sexual reproduction, immune functions, and refractoriness to pathogens. Here, we considered their role in resistance against insecticides. In particular, we assessed how larval infection of a permethrin-resistant and a sensitive colony of Anopheles gambiae by four strains belonging to three different Pseudomonas species affects several life history traits and the impact of the insecticide on the mortality of adults. Our data showed that all four Pseudomonas species persisted in adults until death. The bacteria increased the likelihood that mosquitoes survived 24 hours after exposure to permethrin by up to two-fold. The impact of the bacteria depended on the bacterial species and the mosquito colony: in the resistant colony, all bacteria increased survival by about 2-fold, while in the sensitive colony, only two of the four species increased survival. The benefit with regard to insecticide resistance came with little to no impact on the other traits (i.e., larval mortality, developmental time and adult longevity). Altogether, our results highlight the importance of considering environmental microbial exposure and mosquito microbial communities in epidemiological and vector-control studies, while also suggesting a possible role for Pseudomonas spp. as a symbiont in A. gambiae .