Select Gut Bacteria Promote Mosquito Larval Growth by Contributing Protease Activity and Optimal Ionic Microenvironment for Protein Digestion

Abstract

Mosquitoes are known to harbor a highly functional gut microbiota, which strongly influence its vector competence through regulating nutrition, development, immunity, fecundity, reproduction, resistance to insecticides, etc. Therefore, a thorough understanding of the function of gut microbiota is required to develop novel and more effective vector-control tactics. With an aim to investigating the role of gut associated bacteria in the larval physiology, we conducted experiments using axenic and gnotobiotic larvae of Aedes albopictus. Our results show that gut associated bacteria along with an intact Carbonic Anhydrase (CA) activity is essential for establishment and maintenance of the characteristic gut pH profile of larvae, which in turn is essential for its digestion. Further, we documented that the requirement of ‘live’ bacteria for establishment of gut pH profile cannot be replaced by either bacterial cell-free supernatant or lysate. Interestingly, we observed that not all the members the gut microbiome has the capability to establish gut pH profile, suggesting that different members of the microbiome possibly have different roles in the larval physiology. Our findings thus reveal an important mechanism through which bacteria modulate different phenotypes in mosquito, which in turn impacts their life-history traits.