An initial investigation of the potential association between bacterial symbiosis and insecticide resistance in Blissus insularis (Hemiptera: Blissidae)

Our studies focus on the southern chinch bug (Blissus insularis), which is well known for its rapid development of resistance to major insecticide classes. This species harbors a betaproteobacterial group, Burkholderia spp., in its gastric caeca. Burkholderia are known for abilities to degrade xenobiotic compounds including insecticides. Using the southern chinch bug as a model system, we initiated studies to determine if bacterial gut symbionts mediate the insecticide resistance. Initially, we established bifenthrin-resistant and susceptible chinch bug colonies. Using universal and genus-specific 16S primers, PCR reactions were performed on genomic DNA extracted from caeca and reproductive tracts of individually dissected female chinch bugs. Burkholderia were detected in 94 and 95% of caeca from susceptible and resistant females respectively. In reproductive tracts, 83 and 79% of susceptible and resistant females respectively were detected to harbor Burkholderia. Analyses of amplified 16S rRNA gene sequences showed that each female harbors only one Burkholderia ribotype in its caeca, regardless of its susceptibility to bifenthrin. Conversely, a more diverse bacterial community was found in female reproductive tracts. Some of resistant and susceptible females harbored the identical Burkholderia ribotype in both the caeca and the reproductive tract. To assess the viability of caecal bacteria with/without antibiotic treatment, a fluorescence-based technique (the LIVE/DEAD BacLight Bacterial Viability) was applied. Results showed that levels of viable caecal bacteria of the antibiotic-treated chinch were suppressed but not eliminated. Currently, experiments are being conducted to examine the impact of antibiotic treatments on insecticide susceptibility.