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 Alphaproteobacteria Garrity et al. 2006
         Order Rickettsiales Gieszczykiewicz 1939 (Approved Lists 1980)
           Genus Pseudocaedibacter Quackenbush 1982, incertae sedis