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Reporting Period: The results reported here are from work conducted from April 2002 to October 2003. Xylella fastidiosa (Xf), which causes Pierce’s disease (PD) in grapevines, is transmitted by the glassy-winged sharpshooter (GWSS). Paratransgenesis employs symbiotic bacteria to deliver anti-Xf compounds to disrupt transmission of the pathogen to new host plants. Alcaligenes xylosoxidans denitrificans (Axd) was identified as a potential agent for paratransgenesis because it inhabits the foregut of GWSS, as does Xf, and the xylem of plants. In this report, we describe the interaction of Axd with plants, GWSS predators, and alternate Xf-vectors and report preliminary data on inhibition of transmission by anti-Xf factors. Axd colonized and traveled within 6 host plants, reaching the highest titers in lemon. Axd colonized the foregut region of two alternate Xf-vectors, the blue green and smoke tree sharpshooters, and was not identified in predatory arthropods that fed on Axd-positive GWSS. Disruption of Xf-transmission by GWSS was demonstrated using two reagents, a single chained antibody fragment and an antibiotic peptide