Competitive Exclusion of Phytopathogenic Serratia marcescens from Squash Bug Vectors by the Gut Endosymbiont Caballeronia

• Published in: Applied and environmental microbiology Vol. 88; no. 1; p. e0155021
• Main Authors: Mendiola, Sandra Y, Stoy, Kayla S, DiSalvo, Susanne, Wynn, Cameron L, Civitello, David J, Gerardo, Nicole M
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 11-01-2022
• Subjects: Anasa tristis; Animals; Bacteria; Burkholderiaceae; Caballeronia; Disease control; Disease transmission; Heteroptera; Host-Microbial Interactions; Infections; Insect control; Insecta; Insects; Invertebrate Microbiology; Microorganisms; Natural enemies; Pathogens; Serratia marcescens; Symbionts; Symbiosis; Vectors; Vegetables; host-microbe interactions; competitive exclusion; arthropod vectors; microbial ecology; symbiosis
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.01550-21

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, making them important players in the quest to develop novel vector control strategies. Using the squash bug
, we investigated how the presence of
symbionts affected the persistence and intensity of phytopathogenic Serratia marcescens within the insect vector. We reared insects aposymbiotically and with different
isolates, infected them with S. marcescens, and then sampled the insects periodically to assess the intensity and persistence of pathogen infection. Squash bugs harboring
consistently had much lower-intensity infections and cleared S. marcescens significantly faster than their aposymbiotic counterparts. These patterns held even when we reversed the timing of exposure to symbiont and pathogen. Taken together, these results indicate that
symbionts play an essential role in S. marcescens infection outcomes in squash bugs and could be used to alter vector competence to enhance agricultural productivity in the future.
Insect-microbe symbioses have repeatedly been shown to profoundly impact an insect's ability to vector pathogens to other hosts. The use of symbiotic microbes to control insect vector populations is of growing interest in agricultural settings. Our study examines how symbiotic microbes affect the dynamics of a plant pathogen infection within the squash bug vector
, a well-documented pest of squash and other cucurbit plants and a vector of Serratia marcescens, the causative agent of cucurbit yellow vine disease. We provide evidence that the symbiont
prevents successful, long-term establishment of S. marcescens in the squash bug. These findings give us insight into symbiont-pathogen dynamics within the squash bug that could ultimately determine its ability to transmit pathogens and be leveraged to interrupt disease transmission in this system.