TWITCHING MOTILITY AMONG VARIOUS WILD-TYPE ISOLATES AND PILUS-DEFECTIVE MUTANTS OF XYLELLA FASTIDIOSA

• Author(s): Burr, Thomas; Hoch, Harvey; De La Fuente, Leonardo; Galvani, C.; Hao, G.; Li, Y.;
• Abstract: The genome of Xylella fastidiosa (Xf) contains at least thirty genes responsible for pilus assembly or function. Recently, it was shown that Xf possesses two distinct types of polar pili: long, type IV pili and short, type I pili. It was also demonstrated that the bacteria of the Temecula strain are able to move on a solid agar surface via type IV-pilus mediated twitching motility that results in the presence of a fringe surrounding the expanding bacterial colony. Since our research had been limited to the Temecula strain, and since such colony morphologies had not been previously reported it was not known whether the fringe we observed in culture was an anomaly of the Temecula strain or if it was also a characteristic of other wild-type strains. We therefore examined fourteen isolates from California, Texas, and South Carolina. All but one Xf isolate developed a fringe around the colony periphery, suggesting that twitching motility may be a critical factor in the spread of the bacteria in planta and development of Pierces disease. We further discovered that fringe formation on PW agar is dramatically affected by the concentration of bovine serum albumin (BSA) in the medium. Type IV pilus-defective mutants, e.g., pilB did not develop a colony fringe. Mutants defective for the shorter type I pili, e.g., fimA continued to exhibit a fringe; and, in fact had a wider fringe.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium