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Microbe Profile: Aquifex aeolicus: an extreme heat-loving bacterium that feeds on gases and inorganic chemicals

Abstract : Habitat and fundamental metabolic processes of 'Aquifex aeolicus'. Natural living environment: Aquificae are ubiquitous and profuse in both marine and terrestrial hydrothermal systems, including underwater volcanoes and hot springs. They are predominant in many microbial communities in thermal habitats containing filamentous biomass and in sediments of springs, but are also found in planktonic populations. As chemolithoautotrophs, they play a principal role in the biogeochemical cycles of carbon, sulphur, and nitrogen. 'Aquifex aeolicus' is a marine bacterium isolated near the shallow submarine volcanic vents of the island Vulcano (Italy). It feeds on molecular hydrogen, carbon dioxide, molecular oxygen, and mineral nutrients, releasing only water. Instead of H 2 , inorganic sulphur compounds can also be oxidized, up to sulphate. Energy conservation and carbon assimilation: The respiratory chains in 'A. aeolicus' include hydrogenases (Hase I and Hase II), O 2 reductases (ba 3 and bd oxidases), a number of sulphur oxidoreductase enzymes, and the lipid-soluble quinone 2-demethylmenaquinone-7 (DMK 7). The physiological role of complex I, which might function in reverse to produce NADH, remains to be clarified [1]. An electrochemical ion gradient is used for ATP synthesis, motility or other cellular functions. In 'A. aeolicus', the polar flagellar motor is driven by Na + ions. Biomass components are produced from inorganic carbon (the CO 2 fixing pathways are boxed in grey) via an ancestral form of the reductive tricarboxylic acid cycle (rTCA) and a still-uncharacterized reductive folate pathway (incomplete Wood-Ljungdahl pathway) [2]. The rTCA cycle is driven by a pool of low-potential, reduced ferredoxins (Fd red), the reduction of which is still enigmatic in 'A. aeolicus'.
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Guiral & Giudici-Orticoni, Mic...
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Marianne Guiral, Marie-Thérèse Giudici-Orticoni. Microbe Profile: Aquifex aeolicus: an extreme heat-loving bacterium that feeds on gases and inorganic chemicals. Microbiology, Microbiology Society, 2020, ⟨10.1099/mic.0.001010⟩. ⟨hal-03102751⟩



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