Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           Domain Bacteria Woese et al. 2024
             Kingdom Pseudomonadati (Gibbons and Murray 1978) Oren and Göker 2024
               Phylum Pseudomonadotaᵀ Garrity et al. 2021
                 Class Betaproteobacteria Garrity et al. 2006
                   Order Spirillales Prévot 1940 (Approved Lists 1980)
                     Family Spirillaceaeᵀ Migula 1894 (Approved Lists 1980)
                       1 Genus Spirillumᵀ Ehrenberg 1832 (Approved Lists 1980) [monotypic]
                       2 Genus "Gastrospirillum" McNulty et al. 1989 nom. inval.
                       3 Genus "Titanospirillum" Guerrero et al. 1999 nom. inval.