Sinorhizobium melilotiSymbiosisNitrogen FixationSinorhizobiumMedicago sativaSinorhizobium frediiMedicago truncatulaMedicagoPlant Root NodulationBacterial ProteinsRoot Nodules, PlantGene Expression Regulation, BacterialRhizobiumRhizobiaceaeGenes, BacterialPlant RootsPolysaccharides, BacterialMolecular Sequence DataFabaceaeRhizobium leguminosarumMelilotusDNA, BacterialSequence Analysis, DNALuteolinGenome, BacterialBase SequenceMutagenesis, InsertionalMutation