Little is known about the functions of the principal matrix components and about the role of cell surface structures in the formation and stabilization of Azospirillum biofilms. It is known that as compared with A. brasilense strain Sp245, its flhB1, fabG1, and mmsB1 mutants, defective in flagellar assembly, form biofilms less well. We made comparative study of bacterial aggregation, biofilm formation, and the effect of DNAase on biofilms.