The mosquito midgut microbiota is very dynamic, with
dramatic fluctuations based upon life-stage, nutritional status,
and age [5]. After a blood meal, mosquito commensal bacteria
undergo changes in their population structure to enrich for enteric
gram-negative bacteria capable of surviving the harsh, digestive
environment of the mosquito midgut [5]. Within this nutrient-rich
environment, bacteria reach high numbers at a time that coincides
with ookinete invasion (,24 h post-blood meal) [6], and can
greatly influence the success of Plasmodium parasite development
[6–9]. In addition, the presence of endogenous bacteria is also
thought to prime the mosquito innate immune response to limit
parasite survival [9–11]. Basal expression levels of anti-microbial
genes controlled by mosquito innate immune pathways limit
bacterial proliferation and indirectly contribute to cross immune
protection against Plasmodium parasites [9–12]. In the absence of
midgut microbiota, mosquito susceptibility to Plasmodium infection
is greatly increased [9].