ESTES, AM; PIERSON, EA; University of Arizona, Dept. of Ecology and Evolutionary Biology; 2University of Arizona, Dept. of Plant Pathology and Microbiology: Understanding the interplay between the tephritid olive fly and its bacterial symbionts.

Symbiosis, the physiologically intimate interaction between two genetically distinct organisms, encompasses relationships from parasitic to mutualistic and facultative to obligate. Obligately mutualistic symbioses are often difficult to study, as the two partners rarely survive independently. For example, in obligate insect-bacterial mutualisms, the partners are rarely cultured separately, manipulated and then reintroduced to the symbiosis. The tephritid olive fly, Bactrocera oleae , and its bacterial flora may be an exception. Petri first identified two species of culturable, mutualistic bacteria in B. oleae (1909,1910). Additional work confirmed Petri�s observations using culture dependent methods, but to date, little work has been done to characterize this symbiosis using molecular techniques. We have used 16S rRNA universal prokaryotic primers to identify two bacteria ( Erwinia dacicola and Enterobacter sp. ) in the olive fly. The Enterobacter sp. can be cultured and both bacteria are present in and appear necessary for all life stages. For example, bacteria may assist the monophagous larvae in digesting the many of the unripe olive�s secondary compounds such as verbascosides and oleuropein which are thought to deter insect herbivory and prevent bacterial degradation (Soler-Rivas et al. 2000). Preliminary evidence shows that adults treated with streptomycin, rifampicin, and kanomycin produce offspring that do not survive in unripe olives past the first larval instar. Additionally, adult flies treated with the antibiotics streptomycin and tetracycline did not survive a 10°C heat shock. These preliminary observations suggest that Erwinia dacicola and Enterobacter sp. may be essential to the survival of the olive fly.