Bacteria are the most important food source for the olive fly, Bactrocera oleae (Rossi) in the olive eco system as well as for many Fruit Flies. The major part of ingested bacteria belong to the family Enterobacteriaceae and Pseudomonadaceae which are very common in the environment and on the olive phylloplane. Since adults of the olive fly are actively searching for these micro organisms, especially females in the pre reproductive phase, we postulated that olive fly adults are attracted by volatiles emitted by bacteria. Previous research carried out in field demonstrated how a bacterial filtrate based on Pseudomonas putida culture attracted B. oleae adults to a comparable degree with respect to the commercial bait. This research analyzes the responses of olive fly antennal and palpal olfactory receptors to odors emitted by Pseudomonas putida bacterial filtrate and to volatiles from a host plant by using electrophysiological and behavioral bioassays. Morphological identification of olfactory receptors was also performed as well as identification of the most important volatiles present in the bacterial cue. The identification of new active volatile compounds in the semiochemical system of the olive fly is promising tool for the development of innovative control strategies in areawide management.