Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         [crown] Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           Domain Bacteria Woese et al. 1990 [paraphyletic?]
             Superphylum "Proteobacteria" Craig et al. 2010
               Phylum "Gammaproteobacteria" Garrity et al., 2005 [monotypic]
                 Class Gammaproteobacteriaᵀ Garrity et al. 2005
                   Order Legionellales Garrity et al. 2005
                     Genus Rickettsiella Philip 1956 (Approved Lists 1980), incertae sedis
                       Rickettsiella popilliaeᵀ (Dutky and Gooden 1952) Philip 1956 (Approved Lists 1980)