Sinorhizobium melilotiNitrogen FixationSinorhizobiumSymbiosisMedicago sativaMedicago truncatulaSinorhizobium frediiBacterial ProteinsBacteriaPlant Root NodulationMedicagoRhizobiaceaeGene Expression Regulation, BacterialRoot Nodules, PlantMolecular Sequence DataGenes, BacterialFabaceaePlant RootsGram-Negative BacteriaDNA, BacterialGram-Positive BacteriaRhizobiumPolysaccharides, BacterialRNA, Ribosomal, 16SPhylogenySequence Analysis, DNABacteria, AnaerobicNitrogen IsotopesNitrogen CompoundsGenome, BacterialRhizobium leguminosarumNitrogen CycleSoil MicrobiologyBradyrhizobiumNitrogen DioxideBlood Urea NitrogenMelilotusMutationEscherichia coliDNA, RibosomalBase SequenceCarbonAmino Acid SequenceRNA, BacterialSoybeansMutagenesis, Insertional