Domain Bacteria Woese et al. 1990
   Phylum Proteobacteria Garrity and Holt 2001 see Phylum Proteobacteria Garrity et al. 2005
     Class "Betaproteobacteria" Garrity et al. 2001 nom. ined. see Class Betaproteobacteria Garrity et al. 2006
       Order "Rhodocyclales" see Order Rhodocyclales Garrity et al. 2006
         Family "Rhodocyclaceae" see Family Rhodocyclaceae Garrity et al. 2006
           Genus Azoarcus Reinhold-Hurek et al. 1993
           Genus Propionibacter Meijer et al. 1999 see Genus Propionivibrio Tanaka et al. 1991
           Genus Propionivibrio Tanaka et al. 1991
           Genus Thauera Macy et al. 1993
           Genus Zoogloea Itzigsohn 1868 (Approved Lists 1980)
           1 Genus Rhodocyclus Pfennig 1978 (Approved Lists 1980)