Date of Award


Document Type


Degree Name

Master of Science (MS)


College of Science and Mathematics



Thesis Sponsor/Dissertation Chair/Project Chair

Jeffrey Toney

Committee Member

James Campanella

Committee Member

John Gaynor


Xylella fastidious a, a gram-negative, rod shaped bacterium, causes disease in many economically important plants including citrus, coffee, and grapevine. Xylella fastidiosa is xylem limited and is dependent on insect vectors for transmission. Pierce’s Disease of Vitis vinifere grape, transmitted by an insect vector, poses a serious threat to California vineyards today. The glassy-winged sharp-shooter, Homalodisca coagulata, has caused millions of dollars of damage to the California wine industry in just a few years. There is evidence that Xylella fastidiosa may share the molecular mechanisms through which the bacterium establishes infection with a closely related species, Xanthomonas campestris. A cluster of genes designated as regulation of pathogenicity factors are responsible for extracellular polysaccharide production and have been found in the genome of Xanthanomonas campestris and Xylella fastidiosa. Site-directed disruption of regulation of pathogenicity factor A, using homologous recombination in the Xylella fastidiosa strains Temecula and Napa, exhibited a decrease in extracellular polysaccharide that resulted in the inhibition of biofilm formation.

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