Scientific classification
Domain: Bacteria
Phylum: Aquificae
Class: Aquificae Reysenbach 2002
Order: Aquificales Reysenbach 2002

The Aquificae phylum is a diverse collection of bacteria that live in harsh environmental settings.[1][2] They have been found in hot springs, sulfur pools, and thermal ocean vents. Members of the genus Aquifex, for example, are productive in water between 105 and 138 °C. They are the dominant members of most terrestrial neutral to alkaline hot springs above 56.4 degrees Celsius. They are autotrophs, and are the primary carbon fixers in these environments. They are true bacteria (domain bacteria) as opposed to the other inhabitants of extreme environments, the Archaea.

Molecular signatures and phylogenetic position

Comparative genomic studies have identified 6

  1. ^ Griffiths E, Gupta RS (January 2006). "Molecular signatures in protein sequences that are characteristics of the phylum Aquificae". Int. J. Syst. Evol. Microbiol. 56 (Pt 1): 99–107.  
  2. ^ a b Horiike T, Miyata D, Hamada K; et al. (January 2009). "Phylogenetic construction of 17 bacterial phyla by new method and carefully selected orthologs". Gene 429 (1–2): 59–64.  
  3. ^ a b Griffiths, E. and Gupta, R. S. (2006). Molecular signatures in protein sequences that are characteristics of the phylum Aquificae. International Journal of Systematic and Evolutionary Microbiology. 56:99-107. doi:10.1099/ijs.0.63927-0.
  4. ^ Huber, R. and Hannig, M. (2006) Thermotogales. Prokaryotes 7: 899-922.
  5. ^ Reysenbach, A.-L. (2001) Phylum BII. Thermotogae phy. nov. In: Bergey's Manual of Systematic Bacteriology, pp. 369-387. Eds D. R. Boone, R. W. Castenholz. Springer-Verlag: Berlin.
  6. ^ Klenk, H. P., Meier, T. D., Durovic, P. and others (1999) RNA polymerase of Aquifex pyrophilus: Implications for the evolution of the bacterial rpoBC operon and extremely thermophilic bacteria. J Mol Evol 48: 528-541.
  7. ^ Gupta, R. S. (2000) The phylogeny of Proteobacteria: relationships to other eubacterial phyla and eukaryotes. FEMS Microbiol Rev 24: 367-402.
  8. ^ Ciccarelli, F. D., Doerks, T., von Mering, C., Creevey, C. J., Snel, B., and Bork, P. (2006) Toward automatic reconstruction of a highly resolved tree of life. Science 311: 1283-1287.
  9. ^ Di Giulio, M. (2003) The universal ancestor was a thermophile or a hyperthermophile: Tests and further evidence. J Theor Biol 221: 425-436.
  10. ^ a b c d Griffiths, E. and Gupta, R. S. (2004) Signature sequences in diverse proteins provide evidence for the late divergence of the order Aquificales. International Microbiol 7: 41-52.
  11. ^ Meyer, T. E. and Bansal, A. K. (2005) Stabilization against hyperthermal denaturation through increased CG content can explain the discrepancy between whole genome and 16S rRNA analyses. Biochemistry 44: 11458-11465.
  12. ^ Catalogue of Organisms: Standing the Heat
  13. ^ J.P. Euzéby. "Aquificae".  
  14. ^ Sayers; et al. "Aquificae".  
  15. ^  
  16. ^ Ludwig, W., Euzéby, J., & Whitman W.B. (2008). "Bergey's Taxonomic Outlines: Volume 4 - Draft Taxonomic Outline of the Bacteroidetes, Planctomycetes, Chlamydiae, Spirochaetes, Fibrobacteres, Fusobacteria, Acidobacteria, Verrucomicrobia, Dictyoglomi, and Gemmatimonadetes" (PDF). Bergey's Manual Trust: 15. 


♠ Strain found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LPSN)

Thermosulfidibacter takaii Nunoura et al. 2008


?Phorcysia thermohydrogeniphila Pérez-Rodríguez et al. 2012

?Desulfurobacterium crinifexAlain et al. 2003

Desulfurobacterium thermolithotrophum L'Haridon et al. 1998 (type sp.)

Desulfurobacterium atlanticum L'Haridon et al. 2006

Desulfurobacterium pacificum L'Haridon et al. 2006


T. ruber Huber et al. 2002 (type sp.)

Balnearium lithotrophicum Takai et al. 2003

T. ammonificans Vetriani et al. 2004

T. guaymasensis L'Haridon et al. 2006


P. guaymasensis Götz et al. 2002

P. hydrogeniphila Nakagawa et al. 2003

P. marina Götz et al. 2002 (type sp.)

Venenivibrio stagnispumantis Hetzer et al. 2008

Hydrogenothermus marinus Stöhr et al. 2001


S. yellowstonense Nakagawa et al. 2005

S. kristjanssonii Flores et al. 2008

S. subterraneum Takai et al. 2003 emend. Nakagawa et al. 2005 (type sp.)

S. azorense Aguiar et al. 2004 emend. Nakagawa et al. 2005

S. rodmanii O'Neill et al. 2008


Hydrogenobaculum acidophilum (Shima and Suzuki 1993) Stöhr et al. 2001


Thermothrix azorensis Odintsova EV et al. (1996) [was Burkholderiaceae]

H. subterraneus Takai et al. 2001

H. hydrogenophilus (Kryukov et al. 1984) Stöhr et al. 2001

H. thermophilus Kawasumi et al. 1984 (type sp.)

Thermocrinis minervae Huber et al. 1999

Thermocrinis ruber Huber et al. 1999 (type sp.)

Thermocrinis albus Eder and Huber 2002


A. aeolicusHuber and Stetter 2001

A. pyrophilus Huber and Stetter 1992 (type sp.)


H. calditorris Nakagawa et al. 2004 (type sp.)

H. okinawensis Nunoura et al. 2008

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) [13] and National Center for Biotechnology Information (NCBI)[14] and the phylogeny is based on 16S rRNA-based LTP release 111 by The All-Species Living Tree Project [15] [16]


Along with Thermotogae, members of Aquificae are thermophilic eubacteria.[2]

[12].Proteobacteria has also suggested that Aquificae is closely related to Cavalier-Smith [10]