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

MALAMUD F; TORRES PS; ROXANA R; RIGANO LA; ENRIQUE R; BONOMI H; CASTAGNARO AP; MARANO MR; VOJNOV A

MICROBIOLOGY

MAIK NAUKA/INTERPERIODICA/SPRINGER

Año: 2010

0026-2617

Xanthomonas axonopodis pv. citri (Xac) is the causative agent of citrus canker. Thisbacterium develops a characteristic biofilm on both biotic and abiotic surfaces. Toevaluate the participation of the single flagellum of Xac in biofilm formation,mutants in the fliC (flagellin) and the flgE (hook) genes were generated. Swimmingmotility, assessed on 0.25% agar plates, was markedly reduced in fliC and flgEmutants. However the fliC and flgE mutants exhibited a flagellar-independentsurface translocation on 0.5% agar plates. Mutation of either rpfF or rpfC genes,which encode proteins involved in cell-cell signaling mediated by the diffusiblesignal factor DSF, led to a reduction in both flagellar-dependent and flagellarindependentsurface translocation, indicating a regulatory role for DSF in bothtypes of motility. Confocal laser scanning microscopy analysis of biofilms producedin static culture demonstrated that flagellum is also involved in the formation ofthe mushroom-shaped structures, water channels and dispersion of biofilms. Thepresence of the flagellum was required for mature biofilm development on lemonleaf surface. The absence of flagellin produced a slight reduction in Xacpathogenicity and this reduction was more severe when the complete flagellumstructure was absent.