The role of cell-surface lectins in the aggregation of azospirilla

The mutant strain Azospirillum brasilense Sp7.2.3 with impaired lectin acti vity exhibited poorer cell aggregation than its parent strain A. brasilense Sp7(S) both in the exponential and stationary growth phases. The pretreatm ent of bacterial cells with the specific haptens (L-fucose and D-galactose) of a lectin located at the cell surface of the mutant strain was found to inhibit the aggregation of azospirilla. The specific binding of the A. bras ilense Sp7(S) lectin to the extracellular polysaccharide-containing complex es of this strain was revealed by dot immunoblotting on nitrocellulose memb rane filters. The interaction of the lectins of A. brasilense 75, A. brasil ense Sp7, and A. lipoferum 59b with the polysaccharide-containing complexes that were isolated from these strains was not specific. No interstrain cro ss-interaction between the exopolysaccharides and lectins of azospirilla wa s found. A coflocculation of A. brasilense Sp7 cells with Bacillus polymyxa 1460 cells was shown. The involvement of autogenous lectins in the aggrega tion of bacterial cells is discussed.