Boreskov

PP‐30have led to divergence of last common ancestor of domain Bacteria, containing archaicbicycle, into ancestral orders Aquificales (RC cycle) and Chloroflexales (3‐HP cycle).In common with the above bacterial protometabolic systems, in the primordial archaealautocatalytic chemical network [7] the splitting of function ƒ() is determined by tworeactions of acetate carboxylation with formation of pyruvate +ƒ() or malonate ‐ƒ(), fig. 2.aFig. 2. Negative feedback metabolic system of archaeal common ancestor (a), ● – point ofbifurcation. Branching direction of bicycle reactions (arrows) on the phase diagram СО2 ‐ Н2 (b).The last common ancestor of domain Archaea (subdomain Crenarchaeota) containedthe integrated system of autotrophic carbon dioxide assimilation – 3‐hydroxypropionate/4‐hydroxybutyrate (3‐HP/4‐HB) + reductive dicarboxylate/4‐hydroxybutyrate (RD/4‐HB)bicycle, which became the metabolic basis of ancestral orders of Sulfolobales (3‐HP/4‐HBcycle) as well as Thermoproteales and Desulfurococcales (RD/4‐HB cycle), fig. 2.This work was supported by the Presidium of Russian Academy of Sciences (program No 25).b[1]. Smith, E., Morowitz, H.G. Universality in intermediary metabolism. Proc. Natl Acad. Sci. USA. 2004. V. 101,P. 13168‐13173;[2]. Parmon V. N. The prebiotic phase of the origin of life as seen by a physical chemist. P. 89‐102. In:Biosphere Origin and Evolution (Editors: Dobretsov N., Kolchanov N., Rozanov A., Zavarzin G.). 2008.Springer Science+Business Media, LLC, 421 p.;[3]. Marakushev S.A., Belonogova O.V. The parageneses thermodynamic analysis of chemoautotrophic СО 2fixation archaic cycle components, their stability and self‐organization in hydrothermal systems. J.Theoret. Biol. 2009. V. 257. No. 4. P. 588‐597;[4]. Srinivasan V., Morowitz H.G. The canonical network of autotrophic intermediary metabolism: minimalmetabolome of a reductive chemoautotroph. Biol. Bull. 2009. V. 216. P. 126–130;[5]. Cavalier‐Smith T. Deep phylogeny, ancestral groups and the four ages of life. Phil. Trans. R. Soc. B. 2010. V.365. P. 111–132;[6]. Valas R.E., Bourne P.E. Structural analysis of polarizing indels: an emerging consensus on the root of thetree of life. Biol. Direct. 2009. V. 4. P. 30–45;[7]. Marakushev S.A., Belonogova O.V. Evolution of carbon dioxide archaic chemoautotrophic fixation systemin hydrothermal systems. Dokl. Biochem. Biophys., 2010. V. 433. P. 164–170.187