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Abstract—: The structure and functions of the biopolymers of the matrix of Azospirillum brasilense biofilms formed at the liquid-solid interface were studied. Calcofluor-binding polysaccharides (CBPS) and the complexes containing lipopolysaccharides (LPS) and proteinaceous structures were shown to fix mature biofilms on solid surfaces and to perform a framework function. The matrix of mature biofilms contained a carbohydrate hapten with a specific affinity to wheat germ agglutinin (WGA), which is important for associative interaction and plant root colonization. The carbohydrate components, predominating over the proteinaceous matrix components, mediate preferable biofilm attachment to hydrophilic surfaces, which is especially evident in the case of A. brasilense Sp245 mutants with impaired flagella formation. This is the first report on the presence of amyloid structures in the biomass of Azospirillum biofilms. [ABSTRACT FROM AUTHOR]

The thickness and antigenic properties of biofilms produced by Azospirillum brasilense Sp245 and its mutants deficient in the synthesis of lipopolysaccharides (Lps) and calcofluor-binding polysaccharides (CBPS) at the interface between water and hydrophilic or hydrophobic solid surfaces were compared. The mutants deficient in acidic LpsI synthesis produce thicker biofilms on hydrophilic surfaces. Biofilms produced on hydrophobic surfaces by bacteria that are unable to synthesize CBPS are less pronounced. Defects in CBPS production in Azospirillum mutants with impaired flagellar motility can cause adverse effects on the cell ability to attach to hydrophobic and hydrophilic surfaces. The loss of the neutral LpsII antigen by the mutants capable of producing CBPS does not affect their behavior on hydrophobic surfaces, which is probably due to the compensatory increase in the total polysaccharide production. The fundamental change in the Lps structure correlates with the activation of biofilm formation by the relevant mutants on hydrophilic and hydrophobic surfaces. [ABSTRACT FROM AUTHOR]