XYLEM FLUID CHEMISTRY MEDIATION OF PIERCES DISEASE: STIMULATION OF AGGREGATION AND BIOFILM FORMATION

• Author(s): Anderson, Peter;
• Abstract: Xylella fastidiosa (Xf) is the causal agent of Pierces disease in grapevines. The mechanisms of pathogenicity are largely due to occlusion of xylem vessels by aggregation of Xf and biofilm formation. Our previous work has documented the effects of xylem constituents on both Xf proliferation and biofilm formation. This current research utilizes 1) addition of xylem constituents to defined media in-vitro, and 2) exposure of Xf to xylem fluids of different Vitis germplasms to investigate effects of xylem components on Xf (growth and biofilm formation. Xylem fluid is typically low in O)2 and our in-vitro studies have established the capability of Xf to grow under hypoxic conditions. The growth in the defined (minimal) media is often superior or equal under the oxygen-limited conditions as compared to the air-saturated media. These effects were found to be variable with Xf (strain and media formulation indicating interactive effects between O)2 (and specific xylem components.) Short term (1 hour) to long term (12 days) exposure of Xf to Vitis xylem fluids showed highly significant differences in both Xf growth rates and biofilm formation dependent on Vitis genotype. Xf growth in Vitis xylem fluid was correlated to the concentration of the organic acid citric acid, many of the amino acids including glutamic acid, glutamine, histidine, valine, methionine, isoleucine and phenylalanine and inorganic ions including copper, magnesium, phosphorous and zinc. Biofilm formation was also correlated to specific xylem constituents. Our next experiments will test the growth and biofilm formation of Xf in response to changing the concentration of these constituents noted above in xylem fluid so that the role of each constituent can be assessed.
• Publication Date: Nov 2006
• Journal: 2006 Pierce's Disease Research Symposium