Bacterial communities in carnivorous pitcher plants colonize and persist in inquiline mosquitoes

The leaves of carnivorous pitcher plants harbor diverse communities of inquiline species, including bacteria and larvae of the pitcher plant mosquito (Wyeomyia smithii), which aid the plant by processing captured prey. Despite the growing appreciation for this microecosystem as a tractable model in which to study food web dynamics and the moniker of W. smithii as a 'keystone predator', very little is known about microbiota acquisition and assembly in W. smithii mosquitoes or the impacts of W. smithii-microbiota interactions on mosquito and/or plant fitness.

In this study, we used high throughput sequencing of bacterial 16S rRNA gene amplicons to characterize and compare microbiota diversity in field- and laboratory-derived W. smithii larvae. We then conducted controlled experiments in the laboratory to better understand the factors shaping microbiota acquisition and persistence across the W. smithii life cycle. Methods were also developed to produce axenic (microbiota-free) W. smithii larvae that can be selectively recolonized with one or more known bacterial species in order to study microbiota function. Our results support a dominant role for the pitcher environment in shaping microbiota diversity in W. smithii larvae, while also indicating that pitcher-associated microbiota can persist in and be dispersed by adult W. smithii mosquitoes. We also demonstrate the successful generation of axenic W. smithii larvae and report variable fitness outcomes in gnotobiotic larvae monocolonized by individual bacterial isolates derived from naturally occurring pitchers in the field.

This study provides the first information on microbiota acquisition and assembly in W. smithii mosquitoes. This study also provides the first evidence for successful microbiota manipulation in this species. Altogether, our results highlight the value of such methods for studying host-microbiota interactions and lay the foundation for future studies to understand how W. smithii-microbiota interactions shape the structure and stability of this important model ecosystem.