[organisms] see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Domain Bacteria Woese et al. 1990
     Phylum "Aquificae" Reysenbach 2001
       Class "Aquificae" Reysenbach 2002
         Order Aquificales Reysenbach 2002
           Family Aquificaceae Reysenbach 2002
             1 Genus Aquifex Huber and Stetter 1992
             2 Genus Hydrogenivirga Nakagawa et al. 2004
             3 Genus Hydrogenobaculum Stöhr et al. 2001
             4 Genus Hydrogenobacter Kawasumi et al. 1984
             4.0 Genus Calderobacterium Kryukov et al. 1984 see Genus Hydrogenobacter Kawasumi et al. 1984
             5 Genus Hydrogenothermus Stöhr et al. 2001
             6 Genus Persephonella Götz et al. 2002
             7 Genus Sulfurihydrogenibium Takai et al. 2003
             8 Genus Thermocrinis Huber et al. 1999