Rhizobium attachment to clover roots

The adhesion of rhizobia to surfaces of clover roots was examined by an indirect plate-counting assay and phase-contrast microscopy. The number of Rhizobium trifolii cells attached to clover root segments increased in approximately linear fashion during the first hour of incubation, but did not change appreciably thereafter. The addition of 30 mM-2-deoxy-D-glucose, which effectively inhibits binding of clover root lectin, did not promote the release of previously attached bacteria nor inhibit subsequent attachment to either root segments or root hairs. Rhizobia of several heterologous species attached to clover roots in numbers comparable to those of strains of R. trifolii, the homologous species. These results indicate that rhizobia have effective mechanisms of adhesion to non-host roots and that clover lectin contributed little or nothing to attachment under the conditions examined.