They contain large Sym plasmids that bear nod genes coding for factors that induce cortical cell div
They contain large Sym plasmids that bear nod genes coding for factors that induce cortical cell division, and their gene expression is modified by uptake of flavonoids.  Following the recognition and attachment steps mediated by the protein rhicadhesin, they multiply in infection threads.  Effective strains produce large structures whose reddish color comes from the oxygen buffer leghemoglobin, which is partially encoded in the host plant.  FTP name these gram-negative bacteria that form symbiotic relationships with legumes, producing nitrogen-fixing root nodules.
They contain large Sym plasmids that bear nod genes coding for factors that induce cortical cell division, and their gene expression is modified by uptake of flavonoids.  
Rhizobium or Rhizobia