The environment in which organisms develop profoundly influences their life history, shaping traits such as development, immunity, and reproduction. Understanding environmental factors, such as microbial communities, is therefore essential for predicting an individual’s lifespan and performance in the environment. In this study, we exposed Anopheles gambiae, the primary malaria vector, to four bacterial species of the genus Pseudomonas, commonly found in water bodies where mosquito larvae develop. Since mosquito larvae primarily feed on bacteria in their early days, we investigated how oral exposure to Pseudomonas during the aquatic stage affects mosquito life-history traits.

We observed that all four Pseudomonas species could persist within adult mosquitoes until their death but at no cost to development or survival. More importantly, our findings reveal that mosquitoes raised in the presence of Pseudomonas exhibit increased resistance to permethrin, a common insecticide. Given Pseudomonas persistence within the mosquito, we believe this protection can extend throughout their lifetime. While this protective effect is species-dependent, it can provide up to a twofold increase in resistance. Remarkably, this increased insecticide resistance incurs little to no cost in survival or development, suggesting a possible coevolutionary relationship or even symbiosis.

Pseudomonas species have been shown to have detoxification properties in vitro and in vivo across many hosts. Our study shows for the first time that this detoxification characteristic of Pseudomonas can be extended to the mosquito host An. gambiae. Moreover, given the host and microbes' geographical distribution, these host and microbe species likely overlap in nature and, therefore, might have a common coevolutionary history. 

This study underscores the importance of considering the ecological context of model organisms and highlights its relevance for vector biology research. These findings contribute to a better understanding of mosquito biology and may inform the design of more effective vector-borne disease control strategies.