procaryotes
   Domain Bacteria Woese et al. 1990 stat. inval. see Domain Bacteria Woese et al. 2024
     Phylum Aquificae Reysenbach 2002 stat. inval. see Phylum Aquificota Reysenbach 2021
       Class Aquificae Reysenbach 2001 nom. inval. see Class Aquificae Reysenbach 2002
         Order Aquificales Reysenbach 2001 nom. inval. see Order Aquificales Reysenbach 2002
           Family Aquificaceae Reysenbach 2001 nom. inval. see Family Aquificaceae Reysenbach 2002
             Genus Aquifex Huber and Stetter 1992