CHARACTERIZATION OF FIMBRIAE PRODUCTION AND ATTACHMENT OF FIMA- AND FIMFMUTANTS OF XYLELLA FASTIDIOSA IN VITRO

• Author(s): Lindow, Steven; Feil, Helene; Purcell, Alexander;
• Abstract: Xylella fastidiosa is a Gram-negative bacterium which causes serious diseases of plants such as Pierces disease (PD) of grape (Vitis vinifera L.), citrus variegated chlorosis (CVC), and almond leaf scorch and colonizes many other plant hosts as well as insect vectors (Purcell 1997). The complete genome sequences of several strains of this organism are now available and provide the base material to study the function of most genes in this organism. X. fastidiosa is known to produce fimbriae to attach unipolarly to cell surfaces (Purcell et al. 1979, Feil et al. 2002). The fimbrial genes are clustered in an operon containing 6 open reading frames (ORFs) (Bhattacharyya et al. 2002). Several of these ORFs have been identified to have homology with genes of other organisms that were shown to be involved in the production of fimbriae (Bhattacharyya et al. 2002). Fimbriae- and pili-mediated attachment of bacteria to host tissues is important for bacterial colonization and pathogenicity (Hultgren et al. 1996). We investigated the role of fimbriae and adhesins in the virulence of X. fastidiosa to plants such as grape. The aim of this study was to determine the importance of fimbriae on the attachment of X. fastidiosa to xylem vessels. Two fimbrial mutants, FimA- and FimF- (a homolog to the adhesin MrkD) were produced and further characterized (Feil et al. 2002). Pathogenicity test showed that the mutants were still virulent in grapes. Research is still underway to determine to what extent the process of colonization of plants is altered in FimA- and FimF- mutants. We expect that the speed with which the cells move through the plant and the time before symptom development is altered in the mutants; detailed measures of pathogen populations of the wild-type and mutant strains is underway in inoculated plants to determine these features. We described here the results of several attachment assays used to further characterize the attachment of these mutants compared to the attachment of the wild type to various substrates.
• Publication Date: Dec 2002
• Journal: 2002 Pierce's Disease Research Symposium