procaryotes
   Domain Bacteria Woese et al. 1990
     Phylum Thermotogae Reysenbach 2001
       Class Thermotogae Reysenbach 2001 see Class Thermotogae Reysenbach 2002
         Order Thermotogales Reysenbach 2001 see Order Thermotogales Reysenbach 2002
           Family Thermotogaceae Reysenbach 2001 see Family Thermotogaceae Reysenbach 2002
             Genus Fervidobacterium Patel et al. 1985