The identification of direct transstadial transmission bacteria in Aedes aegypti (Diptera: Culicidae)

Larval stage mosquitoes host low diversity communities of bacteria in their digestive tract that often vary among individuals and species as a function of collection site and other factors. Adult mosquitoes also have a gut microbiota but how these communities are acquired is incompletely understood. Some evidence indicates adults acquire some community members from larvae by transstadial transmission while other community members are acquired by feeding. Aedes aegypti is a container breeding species that can vector several arboviruses to humans. In this study, we examined how adult A. aegypti acquire a gut microbiota by conducting experiments using conventionally reared larvae with an undefined microbiota, gnotobiotic larvae with a defined gut microbiota of 10 bacterial species, and axenic larvae with no gut microbiota. Results showed that most bacteria in larvae are not directly transmitted from larvae to adults but rather are acquired through adults imbibing water immediately after emergence from the pupal stage. However, one bacterium, Elizabethkingia meningospetica, was directly transmitted from larvae to adults by transstadial transmission. Results further showed that adult females transfer E. meningospetica to the surface of oviposited eggs indicating this bacterium can also potentially be transmitted to offspring.