Assessing gut microbiota diversity and functional potential in resistant and susceptible strains of the mediterranean fruit fly

The Mediterranean fruit fly (Ceratitis capitata) is a destructive polyphagous pest that affects many agricultural crops. While insecticides are commonly used to control its populations, the widespread and excessive use of these chemicals has led to increased resistance globally. Gut microbiota may influence insect behavior and physiology, potentially contributing to this resistance. In this study, high throughput 16S rRNA sequencing was performed to characterize the gut microbiota of both insecticide-susceptible and insecticide-resistant strains of C. capitata, aiming to investigate the potential role of symbiotic bacteria in the medfly resistance development in. Three resistant strains were selected under laboratory conditions by exposing the adult-rearing diet to increasing concentrations of malathion, dimethoate, and spinosad over successive generations. Principal coordinate analysis (PCoA) and Non-metric Multidimensional Scaling (NMDS) analyses revealed significant differences in gut microbiota structure between resistant and susceptible strains (p < 0.001). Insecticide-resistant strains showed a microbiota composition shift upon insecticide exposure. Notably, Serratia spp. and Buttiauxella spp. exhibited a sharp decline in resistant strains, while Enterococcus spp. and Klebsiella spp. showed a significant increase (p < 0.001). Resistant strains showed lower bacterial richness and diversity, suggesting an enrichment of bacteria that have a competitive advantage under insecticide selection pressure. Functional predictions indicated distinct metabolic differences, with resistant strains displaying enhanced activities related to xenobiotic biodegradation and metabolism. This suggests a potential association between these bacteria and insecticide resistance; however, further studies are necessary to determinate whether these bacteria directly contribute to the degradation or detoxification of insecticides.