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

MALAMUD F; TORRES PS; ROESCHLIN R; RIGANO LA,; ENRIQUE R; BONOMI HR; CASTAGNARO AP; MARANO MR; VOJNOV AA

MICROBIOLOGY-UK

SOC GENERAL MICROBIOLOGY

Año: 2011 vol. 157 p. 819 - 829

1350-0872

Xanthomonas axonopodis pv. citri (Xac) is the causative agent of citrus canker. This bacterium develops a characteristic biofilm on both biotic and abiotic surfaces. To evaluate the participation of the single flagellum in biofilm formation, mutants in the fliC (flagellin) and the flgE (hook) genes were generated. Swimming motility, assessed on 0.25% agar plates, was markedly reduced in fliC and flgE mutants. However the fliC and flgE mutants exhibited a flagellar-independent surface translocation on 0.5% agar plates. Mutation of either rpfF or rpfC, which encode proteins involved in cell-cell signaling mediated by the diffusible signal factor DSF, led to a reduction in both flagellar-dependent and flagellar-independent surface translocation, indicating a regulatory role for DSF in both types of motility. Confocal laser scanning microscopy analysis of biofilms produced in static culture indicated that flagellum is also involved in the formation of the mushroom-shaped structures, water channels and dispersion of biofilms. The presence of the flagella was required for mature biofilm development on lemon leaf surface. The absence of flagellin produced a slight reduction in Xac pathogenicity and this reduction was more severe when the complete flagella structure was absent.