The Xanthomonas axonopodis pv. citri flagellum is required for mature biofilm and canker development

MALAMUD, F.; TORRES, P.S.; ROESCHLIN, R.; RIGANO, L.A.; ENRIQUE, R.; BONOMI, H.R.; CASTAGNARO, A.P.; MARANO, M.R.; VOJNOV, A.A

MICROBIOLOGY

MAIK NAUKA/INTERPERIODICA/SPRINGER

Lugar: Kiev; Año: 2011 vol. 157 p. 819 - 829

0026-2617

Xanthomonas axonopodis pv. citri (Xac) is the causative agent of citrus canker. This bacteriumdevelops a characteristic biofilm on both biotic and abiotic surfaces. To evaluate the participationof the single flagellum of Xac in biofilm formation, mutants in the fliC (flagellin) and the flgE (hook)genes were generated. Swimming motility, assessed on 0.25 % agar plates, was markedlyreduced in fliC and flgE mutants. However, the fliC and flgE mutants exhibited a flagellarindependentsurface translocation on 0.5 % agar plates. Mutation of either the rpfF or the rpfCgene, which both encode proteins involved in cell?cell signalling mediated by diffusible signalfactor (DSF), led to a reduction in both flagellar-dependent and flagellar-independent surfacetranslocation, indicating a regulatory role for DSF in both types of motility. Confocal laser scanningmicroscopy of biofilms produced in static culture demonstrated that the flagellum is also involvedin the formation of mushroom-shaped structures and water channels, and in the dispersion ofbiofilms. The presence of the flagellum was required for mature biofilm development on lemon leafsurfaces. The absence of flagellin produced a slight reduction in Xac pathogenicity and thisreduction was more severe when the complete flagellum structure was absent.