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| binomial_authority = [[Robert Huber|Huber]] and [[Karl Stetter|Stetter]], 1992 – NB: Neither validly nor effectively published.
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| binomial_authority = [[Robert Huber|Huber]] and [[Karl Stetter|Stetter]], 1992 – NB: Neither validly nor effectively published.
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“””’Aquifex aeolicus””'” is a [[
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“””’Aquifex aeolicus””'” is a [[chemolithoautotroph]]ic, [[Gram-negative bacteria|Gram-negative]], motile, [[Hyperthermophile|hyperthermophilic]] [[bacterium]].<ref name=”:02″>{{Cite journal|last=Huber, R., Swanson, R., Deckert, G., Warren, P., Gaasterland, T., Young, W., Lenox, A., Graham, D.|date=1998|title=The complete genome of the hyperthermophilic bacterium Aquifex aeolicus|journal=Nature|volume=392|issue=6674|pages=353–8|bibcode=1998Natur.392..353D|doi=10.1038/32831|pmid=9537320|doi-access=free}}</ref> “”A. aeolicus”” is generally rod-shaped with an approximate length of 2.0-6.0μm and a diameter of 0.4-0.5μm.<ref name=”:02″ /><ref name=”:32″>{{Cite journal|last=Guiral|first=Marianne|last2=Giudici-Orticoni|first2=Marie-Thérèse|date=2021-01-01|title=Microbe Profile: Aquifex aeolicus: an extreme heat-loving bacterium that feeds on gases and inorganic chemicals|url=https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.001010|journal=Microbiology|language=en|volume=167|issue=1|doi=10.1099/mic.0.001010|issn=1350-0872}}</ref> “”A. aeolicus”” is neither validly nor effectively published and, having no standing in nomenclature, should be styled in quotation marks. It is one of a handful of species in the [[Aquificae]] [[phylum]], an unusual group of thermophilic bacteria that are thought to be some of the oldest species of bacteria, related to filamentous bacteria first observed at the turn of the century. “”A. aeolicus”” is also believed to be one of the earliest diverging species of thermophilic bacteria.<ref name=”:5″>{{Cite journal|last=Deckert|first=Gerard|last2=Warren|first2=Patrick V.|last3=Gaasterland|first3=Terry|last4=Young|first4=William G.|last5=Lenox|first5=Anna L.|last6=Graham|first6=David E.|last7=Overbeek|first7=Ross|last8=Snead|first8=Marjory A.|last9=Keller|first9=Martin|last10=Aujay|first10=Monette|last11=Huber|first11=Robert|date=March 1998|title=The complete genome of the hyperthermophilic bacterium Aquifex aeolicus|url=https://www.nature.com/articles/32831|journal=Nature|language=en|volume=392|issue=6674|pages=353–358|doi=10.1038/32831|issn=1476-4687}}</ref> “”A. aeolicus”” grows best in water between 85 °C and 95 °C, and can be found near [[Volcano#Submarine volcanoes|underwater volcanoes]] or [[hot spring]]s. It requires [[oxygen]] to survive but has been found to grow optimally under [[Microaerophile|microaerophilic]] conditions.<ref name=”:02″ /> Due to its high stability against high temperature and lack of oxygen, “”A. aeolicus”” is a good candidate for biotechnological applications as it is believed to have potential to be used as [[hydrogenase]]s in an attractive H2/O2 biofuel cell, replacing chemical catalysts.<ref name=”:22″>{{Cite book|last1=Guiral|first1=M|title=The hyperthermophilic bacterium ”Aquifex aeolicus”: From respiratory pathways to extremely resistant enzymes and biotechnological applications|last2=Prunetti|first2=L|last3=Aussignargues|first3=C|last4=Ciaccafava|first4=A|last5=Infossi|first5=P|last6=Ilbert|first6=M|last7=Lojou|first7=E|last8=Giudici-Orticoni|first8=M. T.|year=2012|isbn=9780123944238|series=Advances in Microbial Physiology|volume=61|pages=125–94|chapter=The Hyperthermophilic Bacterium ”Aquifex aeolicus”|doi=10.1016/B978-0-12-394423-8.00004-4|pmid=23046953}}</ref> This can be useful for improving industrial processes.<ref name=”:22″ />
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== Microbiological Characteristics ==
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”’Morphology”’
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”’Morphology”’
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”’Metabolism”’
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”’Metabolism”’
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As an [[autotroph]], “”A. aeolicus”” has the ability to obtain all necessary carbon by fixing CO<sub>2</sub> from the environment and utilizes molecular hydrogen as an electron/energy source.<ref name=”:02″ /><ref name=”:4″ />Additionally, this bacterium utilizes a reductive [[TCA cycle]]<nowiki/>as it provides the substrates of many bio synthetic pathways. The “”A. aeolicus”” [[genome]] contains encoding genes that together could constituent the TCA pathway: [[fumarate reductase]], [[fumarate hydratase]], [[isocitrate dehydrogenase]], [[malate dehydrogenase]], [[ferredoxin]] [[oxidoreductase]], [[succinate]]-[[Coenzyme A|CoA]] [[ligase]], [[aconitase]] and [[Citrate synthase|citratesynthase]].<ref name=”:02″ /> Moreover, this bacterium uses oxygen, [[hydrogen]], and mineral salts as its primary energy sources. “”A. aeolicus”” can also reduce nitrogen and sulfur.
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As an [[autotroph]], “”A. aeolicus”” has the ability to obtain all necessary carbon by fixing CO<sub>2</sub> from the environment and utilizes molecular hydrogen as an electron/energy source.<ref name=”:02″ /><ref name=”:4″ /> Additionally, this bacterium utilizes a reductive [[TCA cycle]]<nowiki/>as it provides the substrates of many bio synthetic pathways. The “”A. aeolicus”” [[genome]] contains encoding genes that together could constituent the TCA pathway: [[fumarate reductase]], [[fumarate hydratase]], [[isocitrate dehydrogenase]], [[malate dehydrogenase]], [[ferredoxin]] [[oxidoreductase]], [[succinate]]-[[Coenzyme A|CoA]] [[ligase]], [[aconitase]] and [[Citrate synthase|citratesynthase]].<ref name=”:02″ /> Moreover, this bacterium uses oxygen, [[hydrogen]], and mineral salts as its primary energy sources. “”A. aeolicus”” can also reduce nitrogen and sulfur.<ref name=”:4″ />
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Regarding its growth under microaerophilic conditions, ”Aquifex” species have been observed to grow in oxygen concentrations as long as 7.5ppm.<ref name=”:12″>{{Cite journal|last=Reysenbach, L., Wickham, G. S. & Pace, N. R.|date=1994|title=Phylogenetic analysis of the hyperthermophilic pink filament community in Octopus Spring, Yellowstone National Park.|journal=Applied and Environmental Microbiology|volume=60|issue=6|pages=2113–2119|doi=10.1128/AEM.60.6.2113-2119.1994|pmc=201609|pmid=7518219}}</ref> It is hypothesized that this is possible because 1) their oxygen-respiration system was already highly developed before the advent of oxygenic [[photosynthesis]], 2) the ”Aquifex” lineage came to life after there was a rise in atmospheric oxygen, or 3) oxygen respiration was developed, and then transferred among different bacterial lineages, such as ”Aquifex”.<ref name=”:02″ /> In response to oxidative stress, “”A. aeolicus”” possesses protective enzymes such as [[Superoxide dismutase|superoxide]] and [[peroxide]] to counter harmful oxygen species.<ref name=”:5″ />
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Regarding its growth under microaerophilic conditions, ”Aquifex” species have been observed to grow in oxygen concentrations as long as 7.5ppm.<ref name=”:12″>{{Cite journal|last=Reysenbach, L., Wickham, G. S. & Pace, N. R.|date=1994|title=Phylogenetic analysis of the hyperthermophilic pink filament community in Octopus Spring, Yellowstone National Park.|journal=Applied and Environmental Microbiology|volume=60|issue=6|pages=2113–2119|doi=10.1128/AEM.60.6.2113-2119.1994|pmc=201609|pmid=7518219}}</ref> It is hypothesized that this is possible because 1) their oxygen-respiration system was already highly developed before the advent of oxygenic [[photosynthesis]], 2) the ”Aquifex” lineage came to life after there was a rise in atmospheric oxygen, or 3) oxygen respiration was developed, and then transferred among different bacterial lineages, such as ”Aquifex”.<ref name=”:02″ /> In response to oxidative stress, “”A. aeolicus”” possesses protective enzymes such as [[Superoxide dismutase|superoxide]] and [[peroxide]] to counter harmful oxygen species.<ref name=”:5″ />
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== Habitat ==
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“”A. aeolicus”” was originally isolated from underwater volcanic vents near the Aeolic Islands (north of Sicily) and has also been isolated from the hot springs in [[Yellowstone National Park|Yellowstone.]]<ref name=”:4″ />As a hyperthermophile, “”A. aeolicus”” can survive up to 95°C with a temperature optima of 85°C<ref name=”:32″ /> with a [[pH]] optima of 8.0, ranging from 6.8 to 9.0.<ref name=”:32″ />
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“”A. aeolicus”” was originally isolated from underwater volcanic vents near the Aeolic Islands (north of Sicily) and has also been isolated from the hot springs in [[Yellowstone National Park|Yellowstone.]]<ref name=”:4″ /> As a hyperthermophile, “”A. aeolicus”” can survive up to 95 °C with a temperature optima of 85 °C<ref name=”:32″ /> with a [[pH]] optima of 8.0, ranging from 6.8 to 9.0.<ref name=”:32″ />
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== Genomic Properties ==
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””Aquifex aeolicus”” is the first thermophilic bacterium to have its entire genome encoded.<ref name=”:32″ />Comparison of the “”Aquifex aeolicus”” [[genome]] to other organisms showed that around 16% of its genes originated from the [[Archaea]] [[Domain (biology)|domain]]. It is most closely related to the hydrogen-oxidizing bacterium, ”[[Aquifex pyrophilus]]”, and its close relative, ”[[Hydrogenobacter thermophilus]]”.<ref name=”:12″ />
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””Aquifex aeolicus”” is the first thermophilic bacterium to have its entire genome encoded.<ref name=”:32″ /> Comparison of the “”Aquifex aeolicus”” [[genome]] to other organisms showed that around 16% of its genes originated from the [[Archaea]] [[Domain (biology)|domain]]. It is most closely related to the hydrogen-oxidizing bacterium, ”[[Aquifex pyrophilus]]”, and its close relative, ”[[Hydrogenobacter thermophilus]]”.<ref name=”:12″ />
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The genome of “”A. aeolicus”” has been successfully mapped,<ref name=”:02″ /> but was noted to be only one-third the size of the ”[[E. coli]]”genome. The genome of “”A. aeolicus”” is densely packed while no introns or protein splicing elements were found.<ref name=”:5″ /> It possesses a circular chromosome with 1,551,335 bp and has a [[G+C content]] of 43.4%, and contains 1,796 genes.<ref name=”:5″ /> It also contains genes potentially coding for three distinct [NiFe] [[hydrogenase]]s, however, it is thought that the ”Aquifex”hydrogenases I and II function in energy conservation, where as hydrogenase III is more likely required for CO<sub>2</sub>fixation.<ref name=”:32″ /> Additionally, during [[sequencing]], a single [[extra chromosomal element]] (ECE) was identified,<ref name=”:02″ /> suggesting evidence of genetic exchange between the “”A. aeolicus”” [[Chromosome#Prokaryotes|chromosome]] and the ECE.
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The genome of “”A. aeolicus”” has been successfully mapped,<ref name=”:02″ /> but was noted to be only one-third the size of the ”[[E. coli]]”genome. The genome of “”A. aeolicus”” is densely packed while no introns or protein splicing elements were found.<ref name=”:5″ />It possesses a circular chromosome with 1,551,335 bp and has a [[G+C content]] of 43.4%, and contains 1,796 genes.<ref name=”:5″ /> It also contains genes potentially coding for three distinct [NiFe] [[
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Multiple enzymes have been identified for potential future use due to their high stability and capacity to oxidize molecular hydrogen, producing byproducts of heat and water.<ref name=”:32″ /><ref name=”:4″ /> A key enzyme of note is [[Hydrogenase|Hydrogenase I]] which was used to study the relationship of enzymes and electrodes during the development of H2-fed, energy-generating biofuel cells.<ref name=”:32″ /> Researchers have explored the use of another extremely resistant enzyme known as lumazine synthase. The cage-forming enzyme has been explored as potential drug delivery nano carrier as it was engineered to encapsulate other molecules.<ref name=”:32″ />
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Multiple enzymes have been identified for potential future use due to their high stability and capacity to oxidize molecular hydrogen, producing byproducts of heat and water.<ref name=”:32″ /><ref name=”:4″ /> A key enzyme of note is [[Hydrogenase|Hydrogenase I]] which was used to study the relationship of enzymes and electrodes during the development of H2-fed, energy-generating biofuel cells.<ref name=”:32″ />Researchers have explored the use of another extremely resistant enzyme known as lumazine synthase. The cage-forming enzyme has been explored as potential drug delivery nano carrier as it was engineered to encapsulate other molecules.<ref name=”:32″ />
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== References ==
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== References ==
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