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 Hydrogenothermaceae Eder and Huber 2003
             1 Genus Hydrogenothermus Stöhr et al. 2001
             2 Genus Persephonella Götz et al. 2002
             3 Genus Sulfurihydrogenibium Takai et al. 2003
             4 Genus Venenivibrio Hetzer et al. 2008