The impact of the mosquito gut microbiota on regulation of egg formation and malaria infection

PROJECT SUMMARY Malaria is a highly prevalent and deadly disease of humans and other vertebrates, infecting over 200 million people and killing over 600,000 annually. This disease is caused by Plasmodium parasites that are transmitted by Anopheles mosquitoes. Female mosquitoes in this genus feed on vertebrate blood to obtain nutrients for egg production and can acquire malaria parasites when they feed on an infected individual. Plasmodium must then transition through several life cycle stages before becoming infectious to the next host upon which the mosquito feeds. Since female mosquitoes can lay hundreds of eggs in their lifetime, targeting mosquito reproductive physiology to suppress mosquito populations is an attractive avenue for malaria control strategies. Two factors implicated both in egg production and development of malaria parasites in mosquitoes: 1) microorganisms in the digestive tract and 2) insulin signaling (IS) triggered by blood feeding, which regulates nutrient mobilization and packaging into developing eggs. However, whether gut microbes and reproductive physiology influence parasite development independently or by interacting with one another is unknown. My preliminary studies identify insulin-like peptides (ILPs) 3 and 4 as key regulators of egg production in the Indian malaria mosquito An. stephensi. My results also indicate development of the murine malaria parasite P. berghei is accelerated by additional blood meals but infection does not affect mosquito fecundity, suggesting the parasite exploits surplus nutrients. I hypothesize that the mosquito gut microbiota influences development of malaria parasites by modulating mosquito insulin signaling (IS). To test this, I will use techniques developed for aseptic rearing of mosquitoes that lack a microbiota, which will allow me to both assess egg production and malaria infection in the absence of any microbes and identify key species that regulate these processes by inoculating germ-free mosquitoes with simplified microbial communities. Aim 1 will identify microbial species that influence mosquito egg production and determine whether they do so by impacting nutrient assimilation or IS. Aim 2 will elucidate whether microbes that impact IS and egg formation also affect Plasmodium development and whether microbial impacts on IS may modulate parasite growth. My proposed study will provide insights into how the native microbiota and invading parasites interact through modulation of host physiology and potentially contribute to developing techniques for reducing mosquito populations or altering vector competence.