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===Ciclo do ácido cítrico redutivo===
TheO [[Reverseciclo de Krebs cycleinverso|reductiveciclo citricdo acidácido cyclecítrico redutivo]] is theé oxidativeo [[citricciclo aciddo cycleácido cítrico]] runque infunciona reverse.en Itsentido hasinverso beennalgúns foundorganismos, incomo [[anaerobicson organism|anaerobic]]as andbacterias microaerobicanaeróbicas bacteriae microaeróbicas. ItDescubrírono was proposed inen 1966 by Evans, Buchanan ande Arnon, whoque wereestaban workinga withtraballar theno anoxygenicestudo photosyntheticda [[Greenfotosíntese sulfuranoxixénica da [[bacteria|green sulfurverde do bacteriumxofre]] that they called ''Chlorobium thiosulfatophilum''. TheA reductiveeste citricciclo acidás cycleveces isse sometimeslle calledchama theciclo de Arnon-Buchanan. No ciclo cáptase CO<sub>2</sub> e H<sub>2</sub>O e transfórmanse en compostos orgánicos (no ciclo de Krebs normal é ao cyclerevés).<ref name="Evans66">{{cite journal |author=Evans MC, Buchanan BB, Arnon DI |year=1966 |title=A new ferredoxin-dependent carbon reduction cycle in a photosynthetic bacterium |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=55 |issue=4 |pages=928–34 |pmid=5219700 |doi=10.1073/pnas.55.4.928 |pmc=224252|bibcode = 1966PNAS...55..928E }}</ref>
===Vía do acetil-CoA redutiva===
TheA [[vía de Wood-Ljungdahl pathway|reductivevía acetyldo acetil-CoA pathwayredutiva]] operatedopera insó strictlyen anaerobicbacterias bacteriaanaerobias estritas ([[acetogensacetóxeno]]s) ande en archaeaarqueas ([[methanogensmetanóxeno]]s). TheA pathwayvía wasfoi proposedproposta inen 1965 bypor Ljungdahl ande Wood. Theycando wereestaban workinga withestudar thea bacteria [[gramGram-positivepositiva]] produtora de [[aceticácido acidacético]] producing bacterium ''Clostridium thermoaceticum'', which(hoxe is now namedchamada ''[[Moorella thermoacetica]]''.), Hydrogenotrophicpolo methanogenesis,que whichtamén isse onlychama foundvía inde certainWood-Ljungdahl. archaeaA andmetanoxénese accountshidroxenotrófica, frorpropia 80%só ofde globalcertas methanogenesisarqueas, issupón alsoo based80% onde thetoda reductivea acetyl[[metanoxénese]] CoAglobal, pathway.e Theestá pathwaybaseada istamén oftenna referredvía todo as the Woodacetil-LjungdahlCoA pathwayredutiva.<ref name="Ljungdahl65">{{cite journal |author=Ljungdahl L, Wood HG |year=1965 |title=Incorporation of C-14 from carbon dioxide into sugar phosphates, carboxylic acids, and amino acids by Clostridium thermoaceticum |journal=J. Bacteriol. |volume=89 |pages=1055–64 |pmid=14276095 |pmc=277595}}</ref><ref name="Ljungdahl09">
{{cite journal |author=Ljungdahl LG |year=2009 |title=A life with acetogens, thermophiles, and cellulolytic anaerobes |journal=Annu. Rev. Microbiol. |volume=63 |pages=1–25 |doi=10.1146/annurev.micro.091208.073617 |pmid=19575555}}</ref>
===oO ciclo do 3-hidroxipropionato e dous ciclos relacionados===
TheO [[vía do 3-Hydroxypropionate pathwayhidroxipropionato|ciclo do 3-hydroxypropionate cyclehidroxipropionato]] isutilízano utilizedsó ''only''as bybacterias verdes non do xofre ([[Chloroflexi (phylum)|green nonsulfur bacteria]]). ItPropúxose wasen proposed2002 inpara 2002explica foro themetabolismo anoxygenicda photosyntheticbacteria fotosintética anoxixénica ''[[Chloroflexus aurantiacus]]''. NoneNingún ofdos theencimas [[enzymes]]que thatparticipan participateno inciclo thedo 3-hydroxypropionatehidroxipropionato cycleson areespecialmente especiallysensibles oxygenao sensitiveoxíxeno.<ref name="Herter02">
{{cite journal |author=Herter S, Fuchs G, Bacher A, Eisenreich W |year=2002 |title=A bicyclic autotrophic CO<sub>2</sub> fixation pathway in Chloroflexus aurantiacus |journal=J. Biol. Chem. |volume=277 |issue=23 |pages=20277–83 |doi=10.1074/jbc.M201030200 |pmid=11929869}}</ref><ref name="Zarzycki09">
{{cite journal |author=Zarzycki J, Brecht V, Müller M, Fuchs G |year=2009 |title=Identifying the missing steps of the autotrophic 3-hydroxypropionate CO<sub>2</sub> fixation cycle in Chloroflexus aurantiacus |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=106 |issue=50 |pages=21317–22 |doi=10.1073/pnas.0908356106 |pmid=19955419|bibcode = 2009PNAS..10621317Z }}
</ref>
AEncontrouse variantunha ofvariante theda vía do 3-hydroxypropionatehidroxipropionato pathwayna was[[arquea]] aeróbica foundtermoacidófila to operated in aerobic extreme thermoacidophile archaeon[[extremófilo|extrema]] [[Metallosphaera|''Metallosphaera sedula'']]. Esta This pathwayvía, calledchámase theciclo do 3-hydroxypropionatehidroxipropionato/4-hydroxybutyrate cycle hidroxibutirato.<ref name="Berg07">{{cite journal |author=Berg IA, Kockelkorn D, Buckel W, Fuchs G |year=2007 |title=A 3-hydroxypropionate/4-hydroxybutyrate autotrophic carbon dioxide assimilation pathway in Archaea |journal=Science |volume=318 |issue=5857 |pages=1782–6 |doi=10.1126/science.1149976 |pmid=18079405|bibcode = 2007Sci...318.1782B }}</ref> Outra Andvariante yetmáis anotherda variantvía of thedo 3-hydroxypropionatehidroxipropionato pathwayé iso theciclo dicarboxylatedo dicarboxilato/4-hydroxybutyratehidroxibutirato, cycle.que se Itdescubriu wasen discoveredarqueas inanaeróbicas, anaerobice archaeafoi proposto en 2008 para a arquea [[hipertermófilo|hipertermófila]] [[Ignicoccus|''Ignicoccus hospitalis'']].<ref name="Huber08">
It was proposed in 2008 for the hyperthermophile archeon [[Ignicoccus|''Ignicoccus hospitalis'']].<ref name="Huber08">
{{cite journal |author=Huber H, Gallenberger M, Jahn U, Eylert E, Berg IA, Kockelkorn D, Eisenreich W, Fuchs G |year=2008 |title=A dicarboxylate/4-hydroxybutyrate autotrophic carbon assimilation cycle in the hyperthermophilic Archaeum Ignicoccus hospitalis |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=105 |issue=22 |pages=7851–6 |doi=10.1073/pnas.0801043105 |pmid=18511565|bibcode = 2008PNAS..105.7851H }}</ref>
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