Mutation in the ntrR Gene, a Member of the vap Gene Family, Increases the Symbiotic Efficiency of Sinorhizobium meliloti oleh Boglárka Oláh, Erno Kiss, Zoltán Györgypál, Judit Borzi, Gyöngyi Cinege, Gyula Csanádi, Jacques Batut, Ádám Kondorosi, Ilona Dusha