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 Aquificota Reysenbach 2021 [monotypic]
                 Class Aquificiaᵀ corrig. Reysenbach 2002
                   Order Aquificalesᵀ Reysenbach 2002
                     Family Aquificaceaeᵀ Reysenbach 2002
                       1 Genus Aquifexᵀ Huber and Stetter 1992 [monotypic]
                       2 Genus Hydrogenivirga Nakagawa et al. 2004
                       3 Genus Hydrogenobacter Kawasumi et al. 1984
                       4 Genus Hydrogenobaculum Stöhr et al. 2001 [monotypic]
                       5 Genus Pampinifervens Palmer et al. 2026
                       6 Genus Thermocrinis Huber et al. 1999