Impact of fungal isolates on mosquito longevity, arboviral competence, and innate immunity

It is now widely accepted that the microbiome of insects plays important and diverse roles in their biology. However, the fungal portion of microbiota (the mycobiota) is understudied compared to other microorganisms. We, therefore, sought to investigate the mycobiota associated with natural populations of mosquitoes in the genus Aedes from Florida and the impact of yeast isolates on mosquito longevity and vector competence for Zika virus. Nine yeast species were identified belonging primarily to the Saccharomycetes and Dothideomycetes classes. We selected four of the isolates for further study using a colony of Aedes aegypti derived from a natural population from Florida in 2019. To examine effects on survival, cohorts of mosquitoes were exposed to the wild yeast isolates in sugar meals upon emergence, and their survival was tracked for at least thirty days. Yeast strains did not exhibit pathogenic effects on mosquito cohorts compared to unexposed controls. Additionally, yeast-treated Ae. aegypti were challenged with Zika virus in blood meals 5-7 days post-emergence to explore potential mosquito mycobiota impact on vector competence. Saliva and mosquito tissues were collected at days 7 and 14 post-exposure and analyzed by plaque assay. No significant effects of yeast exposure were found, but a preliminary screen of selected innate-immunity genes revealed upregulation of the toll pathway caused by one of the isolates. Therefore, although our experiments showed no significant impacts on mosquito longevity or vector competence, we did find evidence of immune stimulation, suggesting the potential impact of yeasts in shaping mosquito-microbe interactions.