Environmental changes, such as differences in nutrient availability, may cause shifts in the composition of species present in a community as well as changes in the metabolism (e.g. proteins produced) of individuals present. Bacteria that live inside animals (endosymbionts) are ideal to explore organismal response to environmental variation. Endosymbionts must survive a series of structural and nutritional changes during host development. This shift in endosymbiont environment is most striking in insects in which the juvenile stage is a larva and the adult stage is free-flying. The two endosymbionts of the olive fly (Bactrocera oleae) reside in an outpocketing of the digestive system. As the host switches from feeding on olives as larvae to feeding on nectar as adults, the bacteria encounter a different nutrient set. This work will test the following predictions: 1) the relative abundance of species in the endosymbiotic community shifts across host development if one bacterial species is better adapted to the larval versus adult digestive system structures; 2) the proteins produced by the bacterial community shifts in response to structural and nutritional changes during host development; 3) the olive fly endosymbionts have relatively large genomes and specific gene sets to facilitate survival in a dynamic host environment. Studies of the olive fly symbiosis will further the understanding of the ecological and molecular mechanisms mediating symbiont-host interactions. Additionally, specific information gained from this study may facilitate new biological-control methods for the olive fly, a costly agricultural pest.
