Sinorhizobium melilotiSymbiosisNitrogen FixationSinorhizobiumMedicago sativaSinorhizobium frediiMedicago truncatulaMedicagoPlant Root NodulationBacterial ProteinsRoot Nodules, PlantGene Expression Regulation, BacterialRhizobiumRhizobiaceaePlant RootsGenes, BacterialPolysaccharides, BacterialMolecular Sequence DataFabaceaeRhizobium leguminosarumMelilotusLuteolinDNA, BacterialGenome, BacterialSequence Analysis, DNA