Cation-dependent gelation of the acidic extracellular polysaccharides of Rhizobium leguminosarum: A non-specific mechanism for the attachment of bacteria to plant roots

Abstract The extracellular acidic heteropolysaccharides produced by various species of Rhizobium leguminosarum possess the same backbone but have different sidechains. Aqueous solutions of these polysaccharides form gels in the presence of excess of salt and divalent cations are more effective at inducing gelation than are monovalent cations, although the moduli of the gels are similar at comparable ionic strength. Gelation of the extracellular polysaccharide is proposed as a mechanism for attaching the bacteria to the tips of plant roots.