Role of the polysaccharide components of Azospirillum brasilense capsules in bacterial adsorption on wheat seedling roots

Azospirillum brasilense cells deprived of capsular exopolysaccharides compl etely lost their ability to bind wheat germ agglutinin (WGA) and much of th eir ability to attach to wheat seedling roots. The decapsulation of bacteri al cells by washing them with a NaCl solution led to an increase in the rel ative hydrophobicity of the cell surface. The pretreatment of wheat seedlin g roots with N-acetyl-D-glucosamine (GlcNAc) or the GlcNAc-containing polys accharide complexes stripped from Azospirillum cells reduced their attachme nt to the roots. Under the experimental conditions used (3-h incubation of wheat seedling roots with exponential-phase azospirilla), bacterial adsorpt ion is mainly driven by the specific mechanisms attachment of the cells to the roots, whose operation is due to the capsular polysaccharide components and the WGA present on the wheat seedling roots.