Specific adsorption of bacteria to clover root hairs, related to the presence of the plasmid pWZ2 in cells of Rhizobium trifolii.

Rhizobium trifolii strains containing plasmid pWZ2, the genetic element indispensable for nodule induction, showed a strong specific adsorption of cells to clover roots. Elimination of the plasmid pWZ2 from bacteria caused loss of adsorption capability, and this property could be recoverd by introduction of the plasmid into bacterial cells. The results obtained indicate that the plasmid pWZ2 contains gene(s) controlling the first stage of Rhizobium-legume symbiosis which is a specific adsorption of nodule bacteria to a suitable plant host.