Based on 16S ribosomal ribonucleic acid (rRNA) genes sequence comparisons, the order Aquificales represents a very deep phylogenetic branch within the bacterial domain. Some Aquificales relatives have an upper temperature limit of growth at 95°C. Together with members of the order Thermotogales, they represent bacteria with the highest growth temperatures known so far. However, unlike Thermotogales, most of the members of the order Aquificales are aerobic or anaerobic lithoautotrophs, using energy of molecular hydrogen, or of reduced sulfur compounds to support their growth.

Keywords: Aquificales; bacteria; lithoautotrophs; thermophiles; evolution

Figure 1.

Schematic 16S rRNA tree of the domain Bacteria showing the position of the order Aquificales. Reproduced from Reysenbach et al..

Figure 2.

Phylogenetic tree generated using maximum‐likelihood analysis showing the position of families within the Aquificales. Reproduced by permission of the International Union of Microbiological Societies from L'Haridon et al. ().

Figure 3.

Electron micrograph of a platinum‐shadowed, single flagellated cell of Aquifex pyrophilus.

Figure 4.

Scanning electron micrographs of Thermocrinis ruber. (a) Thermocrinis ruber grown on a siliconized cover slide. The flakes in the background of the rod‐shaped cells are silicon. Bar, 2 μm. (b) Long filaments of Thermocrinis ruber, grown in a permanent flow of medium under exposure to air. Bar, 2 μm.



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Further Reading

Beffa T, Blanc M and Aragno M (1996) Obligately and facultatively autotrophic, sulfur‐ and hydrogen‐oxidizing thermophilic bacteria isolated from hot composts. Archives of Microbiology 165: 34–40.

Behammer W, Shao Z, Mages W et al. (1995) Flagellar structure and hyperthermophily: analysis of a single flagellin gene and its product in Aquifex pyrophilus. Journal of Bacteriology 22: 6630–6637.

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Reysenbach AL, Whickham GS and Pace NR (1994) Phylogenetic analysis of the hyperthermophilic pink filament community in Octopus Spring, Yellowstone National Park. Applied and Environmental Microbiology 60: 2113–2119.

Schlegel HG (1989) Aerobic hydrogen‐oxidizing (Knallgas) bacteria. In: Schlegel HG and Bowien B (eds) Autotrophic Bacteria, pp 305–329. Berlin: Springer.

Stetter KO (1996) Hyperthermophilic prokaryotes. FEMS Microbiology Reviews 18: 149–158.

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How to Cite close
Bonch‐Osmolovskaya, Elizaveta(Dec 2008) Aquificales. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000442.pub2]