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
                       1 Rickettsiella chironomi (ex Weiser 1963) Weiss et al. 1984
                       2 Rickettsiella grylli (ex Vago and Martoja 1963) Weiss et al. 1984
                       3 Rickettsiella popilliaeᵀ (Dutky and Gooden 1952) Philip 1956 (Approved Lists 1980)
                       4 Rickettsiella stethorae Hall and Badgley 1957 (Approved Lists 1980)