Biofilm and virulence of Xanthomonas citri subsp. Citri and its detection in canker disease.

ADRIÁN A. VOJNOV

Ribeirão Preto,

Conferencia; Workshop on Xanthomonas citri/Citrus canker; 2011

Universidade Estadual Paulista (UNESP)

Xanthomonas axonopodis pv. citri (Xcc) is the causative agent of citrus canker, an important threat to the citrus industry worldwide. Crystal violet staining and confocal laser scanning microscopy analysis of Xcc strains expressing the green fluorescent protein were used to evaluate attachment and biofilm formation on abiotic and biotic (leaf) surfaces. The extracellular polysaccharide xanthan (EPS) played a key role in the biofilm maturation, survival on leaf surfaces and virulence. Biofilm formation in other bacteria is a flagellar-dependent process. Xac has a unique polar flagellum and the evaluation of its participation in biofilm development was performed by the generation of two mutants: Xcc fliC (flagelin gene) and Xcc flgE (hook gene), both involved in the flagellar structure. Confocal laser scanning microscopy of biofilms produced in static culture demonstrated that the flagellum is also involved in the formation of mushroom-shaped structures and water channels, and in the dispersion of biofilms. The presence of the flagellum was required for mature biofilm development on lemon leaf surfaces. The absence of flagellin produced a slight reduction in Xcc pathogenicity and this reduction was more severe when the complete flagellum structure was absent. A sensitive, specific and fast diagnostic assay for Citrus Bacterial Canker detection is also presented.