A phylogenetic approach to the early evolution of autotrophy: the case of the reverse TCA and the reductive acetyl-CoA pathways Authors Arturo Becerra School of Sciences, National Autonomous University of Mexico, Mexico DF Mario Rivas School of Sciences, National Autonomous University of Mexico, Mexico DF Carlos García-Ferris Department of Biochemistry and Molecular Biology and Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Valencia. Antonio Lazcano School of Sciences, National Autonomous University of Mexico, Mexico DF. Juli Peretó Department of Biochemistry and Molecular Biology and Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Valencia. Keywords: autotrophic pathways, reverse Krebs cycle, Wood–Ljungdahl pathway, origin of life, last common ancestor (LCA, LUCA) Abstract In recent decades, a number of hypotheses on the autotrophic origin of life have been presented. These proposals invoke the emergence of reaction networks leading from CO or CO2 to the organic molecules required for life. It has also been suggested that the last (universal) common ancestor (LCA or LUCA) of all extant cell lineages was a chemolitho-autotrophic thermophilic anaerobe. The antiquity of some carbon fixation pathways, the phylogenetic basal distribution of some autotrophic organisms, and the catalytic properties of iron-sulfur minerals have been advanced in support of these ideas. Here we critically examine the phylogenetic distribution and evolution of enzymes that are essential for two of the most ancient autotrophic means of metabolism: the reductive tricarboxylic acid (rTCA) cycle and the reductive acetyl-CoA pathway. Phylogenetic analysis of citryl-CoA synthetase and of citryl-CoA lyase, key enzymatic components of the rTCA cycle, and of CO dehydrogenase/acetyl-CoA synthase, a key enzyme in the reductive acetyl-CoA pathway, revealed that all three enzymes have undergone major lateral transfer events and therefore cannot be used as proof of the LCA’s metabolic abilities nor as evidence of an autotrophic origin of life. [Int Microbiol 2014; 17(2):91-97]Keywords: autotrophic pathways · reverse Krebs cycle · Wood–Ljungdahl pathway · origin of life · last common ancestor (LCA, LUCA) Downloads PDF Issue Vol. 17 No. 2 (2014) Section Research Articles License Submission of a manuscript to International Microbiology implies: that the work described has not been published before, including publication in the World Wide Web (except in the form of an Abstract or as part of a published lecture, review, or thesis); that it is not under consideration for publication elsewhere; that all the coauthors have agreed to its publication. The corresponding author signs for and accepts responsability for releasing this material and will act on behalf of any and all coauthors regarding the editorial review and publication process.If an article is accepted for publication in International Microbiology, the authors (or other copyright holder) must transfer to the journal the right–not exclusive–to reproduce and distribute the article including reprints, translations, photographic reproductions, microform, electronic form (offline, online) or any other reproductions of similar nature. Nevertheless, all article in International Microbiology will be available on the Internet to any reader at no cost. The journal allows users to freely download, copy, print, distribute, search, and link to the full text of any article, provided the authorship and source of the published article is cited. The copyright owner's consent does not include copying for new works, or resale. In these cases, the specific written permission of International Microbiology must first be obtained.Authors are requested to create a link to the published article on the journal's website. The link must be accompanied by the following text: "The original publication is available on LINK at <http://www.im.microbios.org>. Please use the appropiate URL for the article in LINK. Articles disseminated via LINK are indexed, abstracted, and referenced by many abstracting and information services, bibliographic networks, subscription agencies, library networks, and consortia.
