When the rhizosphere is nitrogen-starved, legumes and rhizobia (soil bacteria)enter intoa symbiosis that enables the fixation of atmospheric dinitrogen. This implies a complex chemical dialogue between partners and drastic changes on both plant roots and bacteria. Several recent works pointed out the importance of rhizobial surface polysaccharides in the establishing of the highly specific symbiosis between symbionts. Exopolysaccharides appear tobe essential for the early infection process.
