Graduate Student Emory University Atlanta, Georgia
Many insects harbor microbial symbiotic partners that offer protection against pathogens, parasitoids, and other natural enemies. Mounting evidence suggests that these symbiotic microbes can play key roles in determining infection outcomes in insect vectors and can either inhibit or facilitate pathogen transmission. We use the squash bug vector Anasa tristis and its associated pathogens and symbionts to study how symbiotic microbes affect pathogen infection outcomes. The squash bug is an agriculturally important pest of plants in the family Cucurbitaceae and a known vector of Serratia marcescens, the causative agent of Cucurbit Yellow Vine Disease (CYVD). Bacteria in the genus Caballeronia have a symbiotic relationship with A. tristis, significantly accelerating their development and increasing their survival. We hypothesized that association with Caballeronia affects the establishment and persistence of S. marcescens in squash bugs. To test this, we reared insects aposymbiotically and with different Caballeronia isolates, infected them with a phytopathogenic strain of S. marcescens, then sampled them periodically to assess the intensity and status of pathogen infection. Squash bugs harboring Caballeronia consistently had much lower-intensity infections and cleared S. marcescens significantly faster than their aposymbiotic counterparts. These patterns held even when we varied the order of exposure to symbiont and pathogen. Our future work will address the mechanisms through which pathogen and symbiont compete within the squash bug as well as the broader implications of our findings on disease spread.
