01780nam a2200313 a 450000100080000000500110000800800410001910000280006024500780008826000430016630000100020949000410021952009230026065000220118365000140120565000290121965000260124865000140127465000130128865300170130170000200131870000210133870000170135970000230137670000180139970000140141770000180143170000170144915702712009-10-21       2006    bl uuuu     u0uu1 u    #d1 aREIS JÚNIOR, F. B. dos  a"Beta-rizóbios"bos novos simbiontes encontrados em espécies de Mimosa.  aPlanaltina, DF: Embrapa Cerradosc2006  a20 p.  a(Embrapa Cerrados. Documentos, 153).  aThe fixation and transformation of atmospheric dinitrogen into ammonia and hence into organic e compounds is a crucial part of the nitrogen cycle. Nitrogenase, the enzyme responsible, has a wide taxonomie distribution in the bacteria and archaea, but is confined to a limited number of species. Among these, rhizobia, whieh form nodules on the roots of legumes, are recognised as the main contributors of biologieally-fixed nitrogen. Until recently, it has been generally accepted that legumes are nodulated exelusively by members of the alfa-proteobaeteria belonging to a number of related genera in the family Rhizobiaceae. In this document we review some results from recent studies that presents the newly-discovered beta-rhizobia which challenge the accepted century-old dogma that only Rhizobium and its relatives can nodulate legumes and provide a biodiversity dimension that was totally unexpected 6 years ago.  anitrogen fixation  asymbiosis  aFixação de Nitrogênio  aLeguminosa Forrageira  aRhizobium  aSimbiose  aFeed legumes1 aFARIA, S. M. de1 aMENDES, I. de C.1 aSIMON, M. F.1 aLOUREIRO, M. de F.1 aELLIOT, G. N.1 aYOUNG, P.1 aSPRENT, J. I.1 aJAMES, E. K.