Procaryotic Genera
   Domain "Bacteria" Woese et al. 1990
     Phylum Proteobacteria Garrity and Holt 2001 see Phylum Proteobacteria Garrity et al. 2005
       Class "Alphaproteobacteria" Garrity and Holt 2001 nom. nud. see Class Alphaproteobacteria Garrity et al. 2006
         1 Order Rhodospirillales Pfennig and Trüper 1971 (Approved Lists 1980)
         2 Order Rickettsiales Gieszczykiewicz 1939 (Approved Lists 1980)
         3 Order "Rhodobacterales" [monotypic] see Order Rhodobacterales Garrity et al. 2006
         4 Order "Sphingomonadales" [monotypic] see Order Sphingomonadales Yabuuchi and Kosako 2006
         5 Order Caulobacterales Henrici and Johnson 1935 (Approved Lists 1980) [monotypic]
         6 Order "Rhizobiales" see Order Rhizobiales Kuykendall 2006