SUMMARY Mosquito associated bacteria have a major impact on larval development, life span, vector competence and mating preferences. Multiple studies have deciphered the taxonomic diversity of bacteria associated with various mosquito species. It has been shown that altered microbiota affects multiple mosquito life traits. Despite these studies, the functional role of individual bacterial taxa and their interactions with each other in the mosquito gut remains unknown. To study the role of individual bacteria from a complex community, targeted modulation of the mosquito microbiota is desired. Bacteriophages provide a perfect tool for selective removal of targeted bacteria from microbiota. This proposal aims to utilize bacteriophages to selectively modulate the mosquito microbiota and study its effect of various mosquito life-history traits. Based on literature and our own studies, we have identified five bacterial taxa that are frequently associated with various mosquito species. In aim 1, we will isolate bacteriophages from various environmental sources capable of infecting selected mosquito gut bacteria. In our preliminary experiments we have already successfully isolated multiple bacteriophages capable of selectively infecting various mosquito gut bacteria. In aim 2, we will use isolated bacteriophages to selectively modulate the microbiota of adult Aedes and Anopheles mosquitoes. The effect of this altered microbiota on mosquito life span, fecundity and vector competence will be studied. In aim 3, we will use isolated bacteriophages to selectively modulate the microbiota in larval breeding water. We will evaluate the effect of altered microbiota on larval development, and vector competence, lifespan and fecundity of adult mosquitoes. Our preliminary data with gnotobiotic larvae has shown that addition of bacteriophages to larval breeding water can affect the larval development. This project will be the first ever use of bacteriophages in the mosquito microbiota research and has the potential to be developed into a novel technique to control mosquito borne diseases.