prokaryotes - bacteria see Domain Bacteria Woese et al. 1990 stat. inval.
   Domain "Bacteria" Woese et al. 1990 stat. inval. see Domain Bacteria Woese et al. 2024
     Phylum "Aquificae" Reysenbach 2002 stat. inval. [monotypic] see Phylum Aquificota Reysenbach 2021
       Class Aquificae Reysenbach 2002 [monotypic]
         Order Aquificales Reysenbach 2002
           Family Aquificaceae Reysenbach 2002
             1 Genus Aquifex Huber and Stetter 1992
             2 Genus Calderobacterium Kryukov et al. 1984 see Genus Hydrogenobacter Kawasumi et al. 1984
             3 Genus Hydrogenivirga Nakagawa et al. 2004
             4 Genus Hydrogenobacter Kawasumi et al. 1984
             5 Genus Hydrogenobaculum Stöhr et al. 2001
             6 Genus Thermocrinis Huber et al. 1999