The Journey of the Bacterial Symbiont Through the Olive Fruit Fly: Lessons Learned and Open Questions

Dysbiosis is a strategy to control insect pests through disrupting symbiotic bacteria essential for their life cycle. The olive fly, Bactrocera oleae, has been considered a suitable system for dysbiosis, as the insect is strictly dependent on its unique symbiont Candidatus Erwinia dacicola. Here, we review older and recent results from studies of the interaction of the symbiont and its host fly. We then discuss possible methods for disrupting the symbiosis as a means to control the fly. Specifically, we summarize studies using microscopy methods that have investigated in great detail the organs where the bacterium resides and it is always extracellular. Furthermore, we discuss how genome sequences of both host and bacterium can provide valuable resources for understanding the interaction and transcriptomic analyses that have revealed important insights that can be exploited for dysbiosis strategies. We also assess experiments where compounds have been tested against the symbiont. The hitherto limited efficacy in decreasing bacterial abundance suggests that novel molecules and/or new ways for the delivery of agents will be important for successful dysbiosis strategies. Finally, we discuss how gene drive methods could be implemented in olive fly control, though a number of hurdles would need to be overcome.