prokaryotes - bacteria see Domain Bacteria Woese et al. 1990
   Domain "Bacteria" Woese et al. 1990
     Phylum "Aquificae" Reysenbach 2001 [monotypic]
       Class Aquificae Reysenbach 2002 [monotypic]
         Order Aquificales Reysenbach 2002
           Family Aquificaceae Reysenbach 2002
             Genus Hydrogenobacter Kawasumi et al. 1984