The gut of the Mediterranean fruit fly Ceratitis capitata accommodates a diverse yet stable community of symbiotic bacteria. The characteristics and properties of this community are affected by maternal inoculum, acquisition of environmental bacteria and by habitat conditions.
Larvae develop inside fruits, a carbohydrate rich and protein poor environment, in which the bacteria contribute to larval nutrition by nitrogen fixation and pectinolytic activity. At the end of the larval phase, a small portion of the rot-associated bacteria remain in the gut of pupating larvae, and ultimately contribute to the formation of the final adult gut microbiota.
We hypothesize that both the fruit and the larvae within it have a major role in shaping and perpetuating bacterial populations.
In this study, a correlation between the number of larvae and the number of bacteria in fruits was found. Using culture based methods, we found that during their development, which is a continuous course of migration and feeding, the larvae spread the inoculum over most of the substrate in the first week after emergence.
By exposing fruits to simultaneous oviposition by aposymbiotic females, and females infected with an antibiotic resistant strain, resistant colonies were isolated from the offspring of both mothers. This demonstrates that horizontal transfer of bacteria or genes occurred within the fruits. The relative role of fruit and larvae in shaping bacterial communities remains to be determined.
