prokaryotes - bacteria see Domain Bacteria Woese et al. 1990
   Domain "Bacteria" Woese et al. 1990
     Phylum "Proteobacteria" Garrity et al. 2005 see Superphylum Proteobacteria Craig et al. 2010
       Class Betaproteobacteria Garrity et al. 2006
         Order Rhodocyclales Garrity et al. 2006 [monotypic]
           Family Rhodocyclaceae Garrity et al. 2006
             Genus Propionibacter Meijer et al. 1999 see Genus Propionivibrio Tanaka et al. 1991