title: On the Origin of Heterotrophy.
abstract: The theory of autotrophic origins of life posits that the first cells on Earth satisfied their carbon needs from CO2. At hydrothermal vents, spontaneous synthesis of methane via serpentinization links an energy metabolic reaction with a geochemical homologue. If the first cells were autotrophs, how did the first heterotrophs arise, and what was their substrate? We propose that cell mass roughly similar to the composition of Escherichia coli was the substrate for the first chemoorganoheterotrophs. Amino acid fermentations, pathways typical of anaerobic clostridia and common among anaerobic archaea, in addition to clostridial type purine fermentations, might have been the first forms of heterotrophic carbon and energy metabolism. Ribose was probably the first abundant sugar, and the archaeal type III RubisCO pathway of nucleoside monophosphate conversion to 3-phosphoglycerate might be a relic of ancient heterotrophy. Participation of chemiosmotic coupling and flavin-based electron bifurcation--a soluble energy coupling process--in clostridial amino acid and purine fermentations is consistent with an autotrophic origin of both metabolism and heterotrophy, as is the involvement of S(0) as an electron acceptor in the facilitated fermentations of anaerobic heterotrophic archaea.
authors.affiliation: Institut für Allgemeine Mikrobiologie, Christian-Albrechts-Universität Kiel, 24118 Kiel, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Schönheit
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, Marburg, Germany; Fachbereich Biologie und Synmikro, Philipps-Universität Marburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Buckel
authors.affiliation: Institute of Molecular Evolution, Heinrich-Heine-University, 40225 Düsseldorf, Germany; Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal. Electronic address: bill@hhu.de.
authors.forename: William F
authors.initials: WF
authors.lastname: Martin
mesh_terms: D001105:Archaea / Q000737:chemistry / Q000378:metabolism; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism; D052818:Autotrophic Processes; D001419:Bacteria / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D005075:Biological Evolution; D002244:Carbon / Q000737:chemistry / Q000378:metabolism; D052836:Heterotrophic Processes; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism; D060086:Hydrothermal Vents; D000069497:Origin of Life
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D002244:Carbon; D006859:Hydrogen
keywords: amino acid fermentations; archaeal type III RubisCO; autotrophic origins; hydrothermal vents; purine fermentations