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Öppinger C, Kremp F, Müller V. Is reduced ferredoxin the physiological electron donor for MetVF-type methylenetetrahydrofolate reductases in acetogenesis? A hypothesis. Int Microbiol 2021; 25:75-88. [PMID: 34255221 PMCID: PMC8760232 DOI: 10.1007/s10123-021-00190-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 01/22/2023]
Abstract
The methylene-tetrahydrofolate reductase (MTHFR) is a key enzyme in acetogenic CO2 fixation. The MetVF-type enzyme has been purified from four different species and the physiological electron donor was hypothesized to be reduced ferredoxin. We have purified the MTHFR from Clostridium ljungdahlii to apparent homogeneity. It is a dimer consisting of two of MetVF heterodimers, has 14.9 ± 0.2 mol iron per mol enzyme, 16.2 ± 1.0 mol acid-labile sulfur per mol enzyme, and contains 1.87 mol FMN per mol dimeric heterodimer. NADH and NADPH were not used as electron donor, but reduced ferredoxin was. Based on the published electron carrier specificities for Clostridium formicoaceticum, Thermoanaerobacter kivui, Eubacterium callanderi, and Clostridium aceticum, we provide evidence using metabolic models that reduced ferredoxin cannot be the physiological electron donor in vivo, since growth by acetogenesis from H2 + CO2 has a negative ATP yield. We discuss the possible basis for the discrepancy between in vitro and in vivo functions and present a model how the MetVF-type MTHFR can be incorporated into the metabolism, leading to a positive ATP yield. This model is also applicable to acetogenesis from other substrates and proves to be feasible also to the Ech-containing acetogen T. kivui as well as to methanol metabolism in E. callanderi.
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Affiliation(s)
- Christian Öppinger
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, 60438, Frankfurt, Germany
| | - Florian Kremp
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, 60438, Frankfurt, Germany
| | - Volker Müller
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, 60438, Frankfurt, Germany.
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102
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Howard CJ, Frost A. Ribosome-associated quality control and CAT tailing. Crit Rev Biochem Mol Biol 2021; 56:603-620. [PMID: 34233554 DOI: 10.1080/10409238.2021.1938507] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Translation is the set of mechanisms by which ribosomes decode genetic messages as they synthesize polypeptides of a defined amino acid sequence. While the ribosome has been honed by evolution for high-fidelity translation, errors are inevitable. Aberrant mRNAs, mRNA structure, defective ribosomes, interactions between nascent proteins and the ribosomal exit tunnel, and insufficient cellular resources, including low tRNA levels, can lead to functionally irreversible stalls. Life thus depends on quality control mechanisms that detect, disassemble and recycle stalled translation intermediates. Ribosome-associated Quality Control (RQC) recognizes aberrant ribosome states and targets their potentially toxic polypeptides for degradation. Here we review recent advances in our understanding of RQC in bacteria, fungi, and metazoans. We focus in particular on an unusual modification made to the nascent chain known as a "CAT tail", or Carboxy-terminal Alanine and Threonine tail, and the mechanisms by which ancient RQC proteins catalyze CAT-tail synthesis.
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Affiliation(s)
- Conor J Howard
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
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103
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Davila AF. Life on Mars: Independent Genesis or Common Ancestor? ASTROBIOLOGY 2021; 21:802-812. [PMID: 33848439 DOI: 10.1089/ast.2020.2397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The possibility of biological transfer between planetary bodies is seldom factored into life detection strategies, although the actuality of such an event would have profound implications for how we interpret potential biosignatures found on other worlds. This article addresses the possibility of life on Mars in the context of a biological transfer and an independent genesis of life. The phylogenetic tree of life on Earth is used as a blueprint to interpret evidence of life and as a guideline to determine the likelihood that potential biosignatures could be expressed by martian organisms. Several transfer scenarios are considered, depending on the timing of transfer with respect to the evolution of life on Earth. The implications of each transfer scenario and an independent genesis of life on the biochemical nature of the resulting martian organisms are discussed. The analysis highlights how conceding the possibility of a biological transfer has practical implications for how we search for evidence of life, both in terms of the quality of potential biosignatures and the likelihood that certain biosignatures might be expressed. It is concluded that a degree of uncertainty on the origin of martian organisms might be unavoidable, particularly in the absence of a biochemical context.
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Affiliation(s)
- Alfonso F Davila
- NASA Ames Research Center, Exobiology Branch, Moffett Field, California, USA
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104
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The Origin(s) of Cell(s): Pre-Darwinian Evolution from FUCAs to LUCA : To Carl Woese (1928-2012), for his Conceptual Breakthrough of Cellular Evolution. J Mol Evol 2021; 89:427-447. [PMID: 34173011 DOI: 10.1007/s00239-021-10014-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Accepted: 05/29/2021] [Indexed: 10/21/2022]
Abstract
The coming of the Last Universal Cellular Ancestor (LUCA) was the singular watershed event in the making of the biotic world. If the coming of LUCA marked the crossing of the "Darwinian Threshold", then pre-LUCA evolution must have been Pre-Darwinian and at least partly non-Darwinian. But how did Pre-Darwinian evolution before LUCA actually operate? I broaden our understanding of the central mechanism of biological evolution (i.e., variation-selection-inheritance) and then extend this broadened understanding to its natural starting point: the origin(s) of the First Universal Cellular Ancestors (FUCAs) before LUCA. My hypothesis centers upon vesicles' making-and-remaking as variation and competition as selection. More specifically, I argue that vesicles' acquisition and merger, via breaking-and-repacking, proto-endocytosis, proto-endosymbiosis, and other similar processes had been a central force of both variation and selection in the pre-Darwinian epoch. These new perspectives shed important new light upon the origin of FUCAs and their subsequent evolution into LUCA.
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105
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Russell MJ. The "Water Problem"( sic), the Illusory Pond and Life's Submarine Emergence-A Review. Life (Basel) 2021; 11:429. [PMID: 34068713 PMCID: PMC8151828 DOI: 10.3390/life11050429] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 04/30/2021] [Accepted: 05/01/2021] [Indexed: 01/10/2023] Open
Abstract
The assumption that there was a "water problem" at the emergence of life-that the Hadean Ocean was simply too wet and salty for life to have emerged in it-is here subjected to geological and experimental reality checks. The "warm little pond" that would take the place of the submarine alkaline vent theory (AVT), as recently extolled in the journal Nature, flies in the face of decades of geological, microbiological and evolutionary research and reasoning. To the present author, the evidence refuting the warm little pond scheme is overwhelming given the facts that (i) the early Earth was a water world, (ii) its all-enveloping ocean was never less than 4 km deep, (iii) there were no figurative "Icelands" or "Hawaiis", nor even an "Ontong Java" then because (iv) the solidifying magma ocean beneath was still too mushy to support such salient loadings on the oceanic crust. In place of the supposed warm little pond, we offer a well-protected mineral mound precipitated at a submarine alkaline vent as life's womb: in place of lipid membranes, we suggest peptides; we replace poisonous cyanide with ammonium and hydrazine; instead of deleterious radiation we have the appropriate life-giving redox and pH disequilibria; and in place of messy chemistry we offer the potential for life's emergence from the simplest of geochemically available molecules and ions focused at a submarine alkaline vent in the Hadean-specifically within the nano-confined flexible and redox active interlayer walls of the mixed-valent double layer oxyhydroxide mineral, fougerite/green rust comprising much of that mound.
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Affiliation(s)
- Michael J Russell
- Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria 7, 10125 Turin, Italy
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106
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Mueller RC, Peach JT, Skorupa DJ, Copié V, Bothner B, Peyton BM. An emerging view of the diversity, ecology and function of Archaea in alkaline hydrothermal environments. FEMS Microbiol Ecol 2021; 97:6021323. [PMID: 33501490 DOI: 10.1093/femsec/fiaa246] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 12/01/2020] [Indexed: 11/15/2022] Open
Abstract
The described diversity within the domain Archaea has recently expanded due to advances in sequencing technologies, but many habitats that likely harbor novel lineages of archaea remain understudied. Knowledge of archaea within natural and engineered hydrothermal systems, such as hot springs and engineered subsurface habitats, has been steadily increasing, but the majority of the work has focused on archaea living in acidic or circumneutral environments. The environmental pressures exerted by the combination of high temperatures and high pH likely select for divergent communities and distinct metabolic pathways from those observed in acidic or circumneutral systems. In this review, we examine what is currently known about the archaea found in thermoalkaline environments, focusing on the detection of novel lineages and knowledge of the ecology, metabolic pathways and functions of these populations and communities. We also discuss the potential of emerging multi-omics approaches, including proteomics and metabolomics, to enhance our understanding of archaea within extreme thermoalkaline systems.
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Affiliation(s)
- Rebecca C Mueller
- Department of Chemical and Biological Engineering, Montana State University,Bozeman, MT 59717, PO Box 173920, USA.,Thermal Biology Institute, Montana State University, Bozeman, MT 59717, PO Box 173142, USA
| | - Jesse T Peach
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, PO Box 173400, USA
| | - Dana J Skorupa
- Department of Chemical and Biological Engineering, Montana State University,Bozeman, MT 59717, PO Box 173920, USA.,Thermal Biology Institute, Montana State University, Bozeman, MT 59717, PO Box 173142, USA
| | - Valerie Copié
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, PO Box 173400, USA.,Thermal Biology Institute, Montana State University, Bozeman, MT 59717, PO Box 173142, USA
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, PO Box 173400, USA.,Thermal Biology Institute, Montana State University, Bozeman, MT 59717, PO Box 173142, USA
| | - Brent M Peyton
- Department of Chemical and Biological Engineering, Montana State University,Bozeman, MT 59717, PO Box 173920, USA.,Thermal Biology Institute, Montana State University, Bozeman, MT 59717, PO Box 173142, USA
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107
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To What Inanimate Matter Are We Most Closely Related and Does the Origin of Life Harbor Meaning? PHILOSOPHIES 2021. [DOI: 10.3390/philosophies6020033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The question concerning the meaning of life is important, but it immediately confronts the present authors with insurmountable obstacles from a philosophical standpoint, as it would require us to define not only what we hold to be life, but what we hold to be meaning in addition, requiring us to do both in a properly researched context. We unconditionally surrender to that challenge. Instead, we offer a vernacular, armchair approach to life’s origin and meaning, with some layman’s thoughts on the meaning of origins as viewed from the biologist’s standpoint. One can observe that biologists generally approach the concept of biological meaning in the context of evolution. This is the basis for the broad resonance behind Dobzhansky’s appraisal that “Nothing in biology makes sense except in the light of evolution”. Biologists try to understand living things in the historical context of how they arose, without giving much thought to the definition of what life or living things are, which for a biologist is usually not an interesting question in the practical context of daily dealings with organisms. Do humans generally understand life’s meaning in the context of history? If we consider the problem of life’s origin, the question of what constitutes a living thing becomes somewhat more acute for the biologist, though not more answerable, because it is inescapable that there was a time when there were no organisms on Earth, followed by a time when there were, the latter time having persisted in continuity to the present. This raises the question of where, in that transition, chemicals on Earth became alive, requiring, in turn, a set of premises for how life arose in order to conceptualize the problem in relation to organisms we know today, including ourselves, which brings us to the point of this paper: In the same way that cultural narratives for origins always start with a setting, scientific narratives for origins also always start with a setting, a place on Earth or elsewhere where we can imagine what happened for the sake of structuring both the problem and the narrative for its solution. This raises the question of whether scientific origins settings convey meaning to humans in that they suggest to us from what kind of place and what kinds of chemicals we are descended, that is, to which inanimate things we are most closely related.
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108
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Katsyv A, Schoelmerich MC, Basen M, Müller V. The pyruvate:ferredoxin oxidoreductase of the thermophilic acetogen, Thermoanaerobacter kivui. FEBS Open Bio 2021; 11:1332-1342. [PMID: 33660937 PMCID: PMC8091585 DOI: 10.1002/2211-5463.13136] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 02/24/2021] [Accepted: 03/02/2021] [Indexed: 12/26/2022] Open
Abstract
Pyruvate:ferredoxin oxidoreductase (PFOR) is a key enzyme in bacterial anaerobic metabolism. Since a low‐potential ferredoxin (Fd2−) is used as electron carrier, PFOR allows for hydrogen evolution during heterotrophic growth as well as pyruvate synthesis during lithoautotrophic growth. The thermophilic acetogenic model bacterium Thermoanaerobacter kivui can use both modes of lifestyle, but the nature of the PFOR in this organism was previously unestablished. Here, we have isolated PFOR to apparent homogeneity from cells grown on glucose. Peptide mass fingerprinting revealed that it is encoded by pfor1. PFOR uses pyruvate as an electron donor and methylene blue (1.8 U·mg−1) and ferredoxin (Fd; 27.2 U·mg−1) as electron acceptors, and the reaction is dependent on thiamine pyrophosphate, pyruvate, coenzyme A, and Fd. The pH and temperature optima were 7.5 and 66 °C, respectively. We detected 13.6 mol of iron·mol of protein−1, consistent with the presence of three predicted [4Fe–4S] clusters. The ability to provide reduced Fd makes PFOR an interesting auxiliary enzyme for enzyme assays. To simplify and speed up the purification procedure, we established a protocol for homologous protein production in T. kivui. Therefore, pfor1 was cloned and expressed in T. kivui and the encoded protein containing a genetically engineered His‐tag was purified in only two steps to apparent homogeneity. The homologously produced PFOR1 had the same properties as the enzyme from T. kivui. The enzyme can be used as auxiliary enzyme in enzymatic assays that require reduced Fd as electron donor, such as electron‐bifurcating enzymes, to keep a constant level of reduced Fd.
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Affiliation(s)
- Alexander Katsyv
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Marie Charlotte Schoelmerich
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Mirko Basen
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Volker Müller
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
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109
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Ameta S, Matsubara YJ, Chakraborty N, Krishna S, Thutupalli S. Self-Reproduction and Darwinian Evolution in Autocatalytic Chemical Reaction Systems. Life (Basel) 2021; 11:308. [PMID: 33916135 PMCID: PMC8066523 DOI: 10.3390/life11040308] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 03/25/2021] [Accepted: 03/27/2021] [Indexed: 11/18/2022] Open
Abstract
Understanding the emergence of life from (primitive) abiotic components has arguably been one of the deepest and yet one of the most elusive scientific questions. Notwithstanding the lack of a clear definition for a living system, it is widely argued that heredity (involving self-reproduction) along with compartmentalization and metabolism are key features that contrast living systems from their non-living counterparts. A minimal living system may be viewed as "a self-sustaining chemical system capable of Darwinian evolution". It has been proposed that autocatalytic sets of chemical reactions (ACSs) could serve as a mechanism to establish chemical compositional identity, heritable self-reproduction, and evolution in a minimal chemical system. Following years of theoretical work, autocatalytic chemical systems have been constructed experimentally using a wide variety of substrates, and most studies, thus far, have focused on the demonstration of chemical self-reproduction under specific conditions. While several recent experimental studies have raised the possibility of carrying out some aspects of experimental evolution using autocatalytic reaction networks, there remain many open challenges. In this review, we start by evaluating theoretical studies of ACSs specifically with a view to establish the conditions required for such chemical systems to exhibit self-reproduction and Darwinian evolution. Then, we follow with an extensive overview of experimental ACS systems and use the theoretically established conditions to critically evaluate these empirical systems for their potential to exhibit Darwinian evolution. We identify various technical and conceptual challenges limiting experimental progress and, finally, conclude with some remarks about open questions.
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Affiliation(s)
- Sandeep Ameta
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Yoshiya J. Matsubara
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Nayan Chakraborty
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Sandeep Krishna
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
| | - Shashi Thutupalli
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560065, India
- International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bangalore 560089, India
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110
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Abstract
The evolution of coenzymes, or their impact on the origin of life, is fundamental for understanding our own existence. Having established reasonable hypotheses about the emergence of prebiotic chemical building blocks, which were probably created under palaeogeochemical conditions, and surmising that these smaller compounds must have become integrated to afford complex macromolecules such as RNA, the question of coenzyme origin and its relation to the evolution of functional biochemistry should gain new impetus. Many coenzymes have a simple chemical structure and are often nucleotide-derived, which suggests that they may have coexisted with the emergence of RNA and may have played a pivotal role in early metabolism. Based on current theories of prebiotic evolution, which attempt to explain the emergence of privileged organic building blocks, this Review discusses plausible hypotheses on the prebiotic formation of key elements within selected extant coenzymes. In combination with prebiotic RNA, coenzymes may have dramatically broadened early protometabolic networks and the catalytic scope of RNA during the evolution of life.
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Affiliation(s)
- Andreas Kirschning
- Institut für Organische Chemie und Biomolekulares Wirkstoffzentrum (BMWZ)Leibniz Universität HannoverSchneiderberg 1B30167HannoverGermany
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111
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The Autotrophic Core: An Ancient Network of 404 Reactions Converts H 2, CO 2, and NH 3 into Amino Acids, Bases, and Cofactors. Microorganisms 2021; 9:microorganisms9020458. [PMID: 33672143 PMCID: PMC7926472 DOI: 10.3390/microorganisms9020458] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/11/2021] [Accepted: 02/19/2021] [Indexed: 01/03/2023] Open
Abstract
The metabolism of cells contains evidence reflecting the process by which they arose. Here, we have identified the ancient core of autotrophic metabolism encompassing 404 reactions that comprise the reaction network from H2, CO2, and ammonia (NH3) to amino acids, nucleic acid monomers, and the 19 cofactors required for their synthesis. Water is the most common reactant in the autotrophic core, indicating that the core arose in an aqueous environment. Seventy-seven core reactions involve the hydrolysis of high-energy phosphate bonds, furthermore suggesting the presence of a non-enzymatic and highly exergonic chemical reaction capable of continuously synthesizing activated phosphate bonds. CO2 is the most common carbon-containing compound in the core. An abundance of NADH and NADPH-dependent redox reactions in the autotrophic core, the central role of CO2, and the circumstance that the core’s main products are far more reduced than CO2 indicate that the core arose in a highly reducing environment. The chemical reactions of the autotrophic core suggest that it arose from H2, inorganic carbon, and NH3 in an aqueous environment marked by highly reducing and continuously far from equilibrium conditions. Such conditions are very similar to those found in serpentinizing hydrothermal systems.
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112
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Wang Q, Steinbock O. Chemical Garden Membranes in Temperature-Controlled Microfluidic Devices. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:2485-2493. [PMID: 33555186 DOI: 10.1021/acs.langmuir.0c03548] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Thin-walled tubes that classically form when metal salts react with sodium silicate solution are known as chemical gardens. They share similarities with the porous, catalytic materials in hydrothermal vent chimneys, and both structures are exposed to steep pH gradients that, combined with thermal factors, might have provided the free energy for prebiotic chemistry on early Earth. We report temperature effects on the shape, composition, and opacity of chemical gardens. Tubes grown at high temperature are more opaque, indicating changes to the membrane structure or thickness. To study this dependence, we developed a temperature-controlled microfluidic device, which allows the formation of analogous membranes at the interface of two coflowing reactant solutions. For the case of Ni(OH)2, membranes thicken according to a diffusion-controlled mechanism. In the studied range of 10-40 °C, the effective diffusion coefficient is independent of temperature. This suggests that counteracting processes are at play (including an increased solubility) and that the opacity of chemical garden tubes arises from changes in internal morphology. The latter could be linked to experimentally observed dendritic structures within the membranes.
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Affiliation(s)
- Qingpu Wang
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Oliver Steinbock
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
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113
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Activating the FeS (001) Surface for CO2 Adsorption and Reduction through the Formation of Sulfur Vacancies: A DFT-D3 Study. Catalysts 2021. [DOI: 10.3390/catal11010127] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
As a promising material for heterogeneous catalytic applications, layered iron (II) monosulfide (FeS) contains active edges and an inert basal (001) plane. Activating the basal (001) plane could improve the catalytic performance of the FeS material towards CO2 activation and reduction reactions. Herein, we report dispersion-corrected density functional theory (DFT-D3) calculations of the adsorption of CO2 and the elementary steps involved in its reduction through the reverse water-gas shift reaction on a defective FeS (001) surface containing sulfur vacancies. The exposed Fe sites resulting from the creation of sulfur vacancies are shown to act as highly active sites for CO2 activation and reduction. Based on the calculated adsorption energies, we show that the CO2 molecules will outcompete H2O and H2 molecules for the exposed active Fe sites if all three molecules are present on or near the surface. The CO2 molecule is found to weakly physisorb (−0.20 eV) compared to the sulfur-deficient (001) surface where it adsorbs much strongly, releasing adsorption energy of −1.78 and −1.83 eV at the defective FeS (001) surface containing a single and double sulfur vacancy, respectively. The CO2 molecule gained significant charge from the interacting surface Fe ions at the defective surface upon adsorption, which resulted in activation of the C–O bonds confirmed via vibrational frequency analyses. The reaction and activation energy barriers of the elementary steps involved in the CO2 hydrogenation reactions to form CO and H2O species are also unraveled.
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114
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Wiechmann A, Trifunović D, Klein S, Müller V. Homologous production, one-step purification, and proof of Na + transport by the Rnf complex from Acetobacterium woodii, a model for acetogenic conversion of C1 substrates to biofuels. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:208. [PMID: 33342435 PMCID: PMC7751120 DOI: 10.1186/s13068-020-01851-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 12/04/2020] [Indexed: 05/25/2023]
Abstract
BACKGROUND Capture and storage of the energy carrier hydrogen as well as of the greenhouse gas carbon dioxide are two major problems that mankind faces currently. Chemical catalysts have been developed, but only recently a group of anaerobic bacteria that convert hydrogen and carbon dioxide to acetate, formate, or biofuels such as ethanol has come into focus, the acetogenic bacteria. These biocatalysts produce the liquid organic hydrogen carrier formic acid from H2 + CO2 or even carbon monoxide with highest rates ever reported. The autotrophic, hydrogen-oxidizing, and CO2-reducing acetogens have in common a specialized metabolism to catalyze CO2 reduction, the Wood-Ljungdahl pathway (WLP). The WLP does not yield net ATP, but is hooked up to a membrane-bound respiratory chain that enables ATP synthesis coupled to CO2 fixation. The nature of the respiratory enzyme has been an enigma since the discovery of these bacteria and has been unraveled in this study. RESULTS We have produced a His-tagged variant of the ferredoxin:NAD oxidoreductase (Rnf complex) from the model acetogen Acetobacterium woodii, solubilized the enzyme from the cytoplasmic membrane, and purified it by Ni2+-NTA affinity chromatography. The enzyme was incorporated into artificial liposomes and catalyzed Na+ transport coupled to ferredoxin-dependent NAD reduction. Our results using the purified enzyme do not only verify that the Rnf complex from A. woodii is Na+-dependent, they also demonstrate for the first time that this membrane-embedded molecular engine creates a Na+ gradient across the membrane of A. woodii which can be used for ATP synthesis. DISCUSSION We present a protocol for homologous production and purification for an Rnf complex. The enzyme catalyzed electron-transfer driven Na+ export and, thus, our studies provided the long-awaited biochemical proof that the Rnf complex is a respiratory enzyme.
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Affiliation(s)
- Anja Wiechmann
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue Str. 9, 60438, Frankfurt am Main, Germany
| | - Dragan Trifunović
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue Str. 9, 60438, Frankfurt am Main, Germany
| | - Sophie Klein
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue Str. 9, 60438, Frankfurt am Main, Germany
| | - Volker Müller
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue Str. 9, 60438, Frankfurt am Main, Germany.
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115
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Abstract
Carbon redox chemistry plays a fundamental role in biology. However, the thermodynamic and physicochemical principles underlying the rise of metabolites involved in redox biochemistry remain poorly understood. Our work introduces the theory and techniques that allow us to quantify and understand the global energy landscape of carbon redox biochemistry. We analyze the space of all possible oxidation states of linear-chain molecules with two to five carbon atoms and generate a detailed atlas of the thermodynamic stability of metabolites in comparison to nonbiological molecules. Although the emergence of life required the underlying chemistry to bootstrap itself out of equilibrium, a quantitative understanding of the environment-dependent thermodynamic landscape of prebiotic molecules will be extremely valuable for future origins of life models. Redox biochemistry plays a key role in the transduction of chemical energy in living systems. However, the compounds observed in metabolic redox reactions are a minuscule fraction of chemical space. It is not clear whether compounds that ended up being selected as metabolites display specific properties that distinguish them from nonbiological compounds. Here, we introduce a systematic approach for comparing the chemical space of all possible redox states of linear-chain carbon molecules to the corresponding metabolites that appear in biology. Using cheminformatics and quantum chemistry, we analyze the physicochemical and thermodynamic properties of the biological and nonbiological compounds. We find that, among all compounds, aldose sugars have the highest possible number of redox connections to other molecules. Metabolites are enriched in carboxylic acid functional groups and depleted of ketones and aldehydes and have higher solubility than nonbiological compounds. Upon constructing the energy landscape for the full chemical space as a function of pH and electron-donor potential, we find that metabolites tend to have lower Gibbs energies than nonbiological molecules. Finally, we generate Pourbaix phase diagrams that serve as a thermodynamic atlas to indicate which compounds are energy minima in redox chemical space across a set of pH values and electron-donor potentials. While escape from thermodynamic equilibrium toward kinetically driven states is a hallmark of life and its origin, we envision that a deeper quantitative understanding of the environment-dependent thermodynamic landscape of putative prebiotic molecules will provide a crucial reference for future origins-of-life models.
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116
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Affiliation(s)
- Andreas Kirschning
- Institut für Organische Chemie und Biomolekulares Wirkstoffzentrum (BMWZ) Leibniz Universität Hannover Schneiderberg 1B 30167 Hannover Deutschland
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117
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Liu L, Zou Y, Bhattacharya A, Zhang D, Lang SQ, Houk KN, Devaraj NK. Enzyme-free synthesis of natural phospholipids in water. Nat Chem 2020; 12:1029-1034. [PMID: 33046841 DOI: 10.1038/s41557-020-00559-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 08/25/2020] [Indexed: 11/09/2022]
Abstract
All living organisms synthesize phospholipids as the primary constituent of their cell membranes. Enzymatic synthesis of diacylphospholipids requires preexisting membrane-embedded enzymes. This limitation has led to models of early life in which the first cells used simpler types of membrane building blocks and has hampered integration of phospholipid synthesis into artificial cells. Here we demonstrate an enzyme-free synthesis of natural diacylphospholipids by transacylation in water, which is enabled by a combination of ion pairing and self-assembly between lysophospholipids and acyl donors. A variety of membrane-forming cellular phospholipids have been obtained in high yields. Membrane formation takes place in water from natural alkaline sources such as soda lakes and hydrothermal oceanic vents. When formed vesicles are transferred to more acidic solutions, electrochemical proton gradients are spontaneously established and maintained. This high-yielding non-enzymatic synthesis of natural phospholipids in water opens up new routes for lipid synthesis in artificial cells and sheds light on the origin and evolution of cellular membranes.
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Affiliation(s)
- Luping Liu
- Department of Chemistry and Biochemistry, University of California, San Diego, CA, USA
| | - Yike Zou
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | - Ahanjit Bhattacharya
- Department of Chemistry and Biochemistry, University of California, San Diego, CA, USA
| | - Dongyang Zhang
- Department of Chemistry and Biochemistry, University of California, San Diego, CA, USA
| | - Susan Q Lang
- School of the Earth, Ocean, and Environment, University of South Carolina, Columbia, SC, USA
| | - K N Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | - Neal K Devaraj
- Department of Chemistry and Biochemistry, University of California, San Diego, CA, USA.
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118
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Steel M, Xavier JC, Huson DH. The structure of autocatalytic networks, with application to early biochemistry. J R Soc Interface 2020; 17:20200488. [PMID: 33023395 DOI: 10.1098/rsif.2020.0488] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Metabolism across all known living systems combines two key features. First, all of the molecules that are required are either available in the environment or can be built up from available resources via other reactions within the system. Second, the reactions proceed in a fast and synchronized fashion via catalysts that are also produced within the system. Building on early work by Stuart Kauffman, a precise mathematical model for describing such self-sustaining autocatalytic systems (RAF theory) has been developed to explore the origins and organization of living systems within a general formal framework. In this paper, we develop this theory further by establishing new relationships between classes of RAFs and related classes of networks, and developing new algorithms to investigate and visualize RAF structures in detail. We illustrate our results by showing how it reveals further details into the structure of archaeal and bacterial metabolism near the origin of life, and provide techniques to study and visualize the core aspects of primitive biochemistry.
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Affiliation(s)
- Mike Steel
- Biomathematics Research Centre, University of Canterbury, Christchurch, New Zealand
| | - Joana C Xavier
- Institute for Molecular Evolution, Heinrich Heine Universität, Dusseldorf, Germany
| | - Daniel H Huson
- Center for Bioinformatics, University of Tübingen, Tubingen, Germany
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119
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Freire MÁ. Phosphorylation and acylation transfer reactions: Clues to a dual origin of metabolism. Biosystems 2020; 198:104260. [PMID: 32987142 DOI: 10.1016/j.biosystems.2020.104260] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/23/2020] [Accepted: 09/23/2020] [Indexed: 12/22/2022]
Abstract
Many theories of the origin of life focus on only one primitive polymer as an archetype of a world paradigm. However, life would have emerged within more complex scenarios where a variety of molecules and diverse polymers interconnected by a few similar chemical reactions. Previous work suggested that the ancestors of all major biopolymers would have arisen from abiotic template independent replication processes. They would have been organized in two closed sets of polymerization cycles: polysaccharides, polyribonucleotides and polyphosphates on one site; and peptides, fatty acids and polyhydroxyalkanoates on the other site. Then, these polymerization reaction cycles integrated into a minimal organization closure. Here, the purpose was to explore which kind of reactions could have supported the chemical networks that led to the early (bio)polymers. As a result, the proposed overview suggests that phosphorylation and acylation transfer reactions would have arisen independently and forged two distinct chemical systems that provided the phosphorylated and carboxylated intermediates used for the synthesis of the corresponding polymers. In this sense, modern metabolism may still reflect its dual nature, probably relying on these two reaction networks from the beginnings.
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Affiliation(s)
- Miguel Ángel Freire
- Instituto Multidisciplinario de Biología Vegetal (IMBIV), CONICET, Universidad Nacional de Córdoba (UNC). Facultad de Ciencias Exactas, Físicas y Naturales. Av. Vélez Sarsfield 299, CC 495, 5000, Córdoba, Argentina.
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120
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Martin WF. Carbon-Metal Bonds: Rare and Primordial in Metabolism. Trends Biochem Sci 2020; 44:807-818. [PMID: 31104860 DOI: 10.1016/j.tibs.2019.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/16/2019] [Accepted: 04/18/2019] [Indexed: 12/13/2022]
Abstract
Submarine hydrothermal vents are rich in hydrogen (H2), an ancient source of electrons and chemical energy for life. Geochemical H2 stems from serpentinization, a process in which rock-bound iron reduces water to H2. Reactions involving H2 and carbon dioxide (CO2) in hydrothermal systems generate abiotic methane and formate; these reactions resemble the core energy metabolism of methanogens and acetogens. These organisms are strict anaerobic autotrophs that inhabit hydrothermal vents and harness energy via H2-dependent CO2 reduction. Serpentinization also generates native metals, which can reduce CO2 to formate and acetate in the laboratory. The enzymes that channel H2, CO2, and dinitrogen (N2) into methanogen and acetogen metabolism are the backbone of the most ancient metabolic pathways. Their active sites share carbon-metal bonds which, although rare in biology, are conserved relics of primordial biochemistry present at the origin of life.
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Affiliation(s)
- William F Martin
- Institute for Molecular Evolution, University of Düsseldorf, 40225 Düsseldorf, Germany.
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121
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Chua SM, Fraser JA. Surveying purine biosynthesis across the domains of life unveils promising drug targets in pathogens. Immunol Cell Biol 2020; 98:819-831. [PMID: 32748425 DOI: 10.1111/imcb.12389] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/30/2020] [Accepted: 07/30/2020] [Indexed: 12/11/2022]
Abstract
Purines play an integral role in cellular processes such as energy metabolism, cell signaling and encoding the genetic makeup of all living organisms-ensuring that the purine metabolic pathway is maintained across all domains of life. To gain a deeper understanding of purine biosynthesis via the de novo biosynthetic pathway, the genes encoding purine metabolic enzymes from 35 archaean, 69 bacterial and 99 eukaryotic species were investigated. While the classic elements of the canonical purine metabolic pathway were utilized in all domains, a subset of familiar biochemical roles was found to be performed by unrelated proteins in some members of the Archaea and Bacteria. In the Bacteria, a major differentiating feature of de novo purine biosynthesis is the increasing prevalence of gene fusions, where two or more purine biosynthesis enzymes that perform consecutive biochemical functions in the pathway are encoded by a single gene. All species in the Eukaryota exhibited the most common fusions seen in the Bacteria, in addition to new gene fusions to potentially increase metabolic flux. This complexity is taken further in humans, where a reversible biomolecular assembly of enzymes known as the purinosome has been identified, allowing short-term regulation in response to metabolic cues while expanding on the benefits that can come from gene fusion. By surveying purine metabolism across all domains of life, we have identified important features of the purine biosynthetic pathway that can potentially be exploited as prospective drug targets.
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Affiliation(s)
- Sheena Mh Chua
- Australian Infectious Diseases Research Centre, School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - James A Fraser
- Australian Infectious Diseases Research Centre, School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia
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122
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Kremp F, Roth J, Müller V. The Sporomusa type Nfn is a novel type of electron-bifurcating transhydrogenase that links the redox pools in acetogenic bacteria. Sci Rep 2020; 10:14872. [PMID: 32913242 PMCID: PMC7483475 DOI: 10.1038/s41598-020-71038-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 08/07/2020] [Indexed: 11/15/2022] Open
Abstract
Flavin-based electron bifurcation is a long hidden mechanism of energetic coupling present mainly in anaerobic bacteria and archaea that suffer from energy limitations in their environment. Electron bifurcation saves precious cellular ATP and enables lithotrophic life of acetate-forming (acetogenic) bacteria that grow on H2 + CO2 by the only pathway that combines CO2 fixation with ATP synthesis, the Wood–Ljungdahl pathway. The energy barrier for the endergonic reduction of NADP+, an electron carrier in the Wood–Ljungdahl pathway, with NADH as reductant is overcome by an electron-bifurcating, ferredoxin-dependent transhydrogenase (Nfn) but many acetogens lack nfn genes. We have purified a ferredoxin-dependent NADH:NADP+ oxidoreductase from Sporomusa ovata, characterized the enzyme biochemically and identified the encoding genes. These studies led to the identification of a novel, Sporomusa type Nfn (Stn), built from existing modules of enzymes such as the soluble [Fe–Fe] hydrogenase, that is widespread in acetogens and other anaerobic bacteria.
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Affiliation(s)
- Florian Kremp
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, 60438, Frankfurt, Germany
| | - Jennifer Roth
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, 60438, Frankfurt, Germany
| | - Volker Müller
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, 60438, Frankfurt, Germany.
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123
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Takagi YA, Nguyen DH, Wexler TB, Goldman AD. The Coevolution of Cellularity and Metabolism Following the Origin of Life. J Mol Evol 2020; 88:598-617. [PMID: 32809045 PMCID: PMC7445158 DOI: 10.1007/s00239-020-09961-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 07/27/2020] [Indexed: 01/09/2023]
Abstract
The emergence of cellular organisms occurred sometime between the origin of life and the evolution of the last universal common ancestor and represents one of the major transitions in evolutionary history. Here we describe a series of artificial life simulations that reveal a close relationship between the evolution of cellularity, the evolution of metabolism, and the richness of the environment. When environments are rich in processing energy, a resource that the digital organisms require to both process their genomes and replicate, populations evolve toward a state of non-cellularity. But when processing energy is not readily available in the environment and organisms must produce their own processing energy from food puzzles, populations always evolve both a proficient metabolism and a high level of cellular impermeability. Even between these two environmental extremes, the population-averaged values of cellular impermeability and metabolic proficiency exhibit a very strong correlation with one another. Further investigations show that non-cellularity is selectively advantageous when environmental processing energy is abundant because it allows organisms to access the available energy, while cellularity is selectively advantageous when environmental processing energy is scarce because it affords organisms the genetic fidelity required to incrementally evolve efficient metabolisms. The selection pressures favoring either non-cellularity or cellularity can be reversed when the environment transitions from one of abundant processing energy to one of scarce processing energy. These results have important implications for when and why cellular organisms evolved following the origin of life.
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Affiliation(s)
- Yuta A Takagi
- Department of Biology, Oberlin College, Oberlin, OH, 44074, USA
| | - Diep H Nguyen
- Department of Biology, Oberlin College, Oberlin, OH, 44074, USA.,Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Tom B Wexler
- Department of Computer Science, Oberlin College, Oberlin, OH, 44074, USA.,Verily Life Sciences, Cambridge, MA, USA
| | - Aaron D Goldman
- Department of Biology, Oberlin College, Oberlin, OH, 44074, USA. .,Blue Marble Space Institute of Science, Seattle, WA, 98154, USA.
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124
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Muchowska KB, Varma SJ, Moran J. Nonenzymatic Metabolic Reactions and Life's Origins. Chem Rev 2020; 120:7708-7744. [PMID: 32687326 DOI: 10.1021/acs.chemrev.0c00191] [Citation(s) in RCA: 123] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Prebiotic chemistry aims to explain how the biochemistry of life as we know it came to be. Most efforts in this area have focused on provisioning compounds of importance to life by multistep synthetic routes that do not resemble biochemistry. However, gaining insight into why core metabolism uses the molecules, reactions, pathways, and overall organization that it does requires us to consider molecules not only as synthetic end goals. Equally important are the dynamic processes that build them up and break them down. This perspective has led many researchers to the hypothesis that the first stage of the origin of life began with the onset of a primitive nonenzymatic version of metabolism, initially catalyzed by naturally occurring minerals and metal ions. This view of life's origins has come to be known as "metabolism first". Continuity with modern metabolism would require a primitive version of metabolism to build and break down ketoacids, sugars, amino acids, and ribonucleotides in much the same way as the pathways that do it today. This review discusses metabolic pathways of relevance to the origin of life in a manner accessible to chemists, and summarizes experiments suggesting several pathways might have their roots in prebiotic chemistry. Finally, key remaining milestones for the protometabolic hypothesis are highlighted.
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Affiliation(s)
| | - Sreejith J Varma
- University of Strasbourg, CNRS, ISIS UMR 7006, 67000 Strasbourg, France
| | - Joseph Moran
- University of Strasbourg, CNRS, ISIS UMR 7006, 67000 Strasbourg, France
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125
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do Nascimento Vieira A, Kleinermanns K, Martin WF, Preiner M. The ambivalent role of water at the origins of life. FEBS Lett 2020; 594:2717-2733. [PMID: 32416624 DOI: 10.1002/1873-3468.13815] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/29/2020] [Accepted: 05/07/2020] [Indexed: 12/15/2022]
Abstract
Life as we know it would not exist without water. However, water molecules not only serve as a solvent and reactant but can also promote hydrolysis, which counteracts the formation of essential organic molecules. This conundrum constitutes one of the central issues in origin of life. Hydrolysis is an important part of energy metabolism for all living organisms but only because, inside cells, it is a controlled reaction. How could hydrolysis have been regulated under prebiotic settings? Lower water activities possibly provide an answer: geochemical sites with less free and more bound water can supply the necessary conditions for protometabolic reactions. Such conditions occur in serpentinising systems, hydrothermal sites that synthesise hydrogen gas via rock-water interactions. Here, we summarise the parallels between biotic and abiotic means of controlling hydrolysis in order to narrow the gap between biochemical and geochemical reactions and briefly outline how hydrolysis could even have played a constructive role at the origin of molecular self-organisation.
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Affiliation(s)
| | | | - William F Martin
- Institute for Molecular Evolution, University of Düsseldorf, Germany
| | - Martina Preiner
- Institute for Molecular Evolution, University of Düsseldorf, Germany
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126
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Martínez-Espinosa RM. Microorganisms and Their Metabolic Capabilities in the Context of the Biogeochemical Nitrogen Cycle at Extreme Environments. Int J Mol Sci 2020; 21:ijms21124228. [PMID: 32545812 PMCID: PMC7349289 DOI: 10.3390/ijms21124228] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 06/12/2020] [Indexed: 12/23/2022] Open
Abstract
Extreme microorganisms (extremophile) are organisms that inhabit environments characterized by inhospitable parameters for most live beings (extreme temperatures and pH values, high or low ionic strength, pressure, or scarcity of nutrients). To grow optimally under these conditions, extremophiles have evolved molecular adaptations affecting their physiology, metabolism, cell signaling, etc. Due to their peculiarities in terms of physiology and metabolism, they have become good models for (i) understanding the limits of life on Earth, (ii) exploring the possible existence of extraterrestrial life (Astrobiology), or (iii) to look for potential applications in biotechnology. Recent research has revealed that extremophilic microbes play key roles in all biogeochemical cycles on Earth. Nitrogen cycle (N-cycle) is one of the most important biogeochemical cycles in nature; thanks to it, nitrogen is converted into multiple chemical forms, which circulate among atmospheric, terrestrial and aquatic ecosystems. This review summarizes recent knowledge on the role of extreme microorganisms in the N-cycle in extremophilic ecosystems, with special emphasis on members of the Archaea domain. Potential implications of these microbes in global warming and nitrogen balance, as well as their biotechnological applications are also discussed.
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Affiliation(s)
- Rosa María Martínez-Espinosa
- Biochemistry and Molecular Biology Division, Agrochemistry and Biochemistry Department, Faculty of Sciences, University of Alicante, Ap. 99, E-03080 Alicante, Spain; ; Tel.: +34-965903400 (ext. 1258)
- Multidisciplinary Institute for Environmental Studies “Ramón Margalef”, University of Alicante, Ap. 99, E-03080 Alicante, Spain
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127
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Merino N, Kawai M, Boyd ES, Colman DR, McGlynn SE, Nealson KH, Kurokawa K, Hongoh Y. Single-Cell Genomics of Novel Actinobacteria With the Wood-Ljungdahl Pathway Discovered in a Serpentinizing System. Front Microbiol 2020; 11:1031. [PMID: 32655506 PMCID: PMC7325909 DOI: 10.3389/fmicb.2020.01031] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 04/27/2020] [Indexed: 01/04/2023] Open
Abstract
Serpentinite-hosted systems represent modern-day analogs of early Earth environments. In these systems, water-rock interactions generate highly alkaline and reducing fluids that can contain hydrogen, methane, and low-molecular-weight hydrocarbons-potent reductants capable of fueling microbial metabolism. In this study, we investigated the microbiota of Hakuba Happo hot springs (∼50°C; pH∼10.5-11), located in Nagano (Japan), which are impacted by the serpentinization process. Analysis of the 16S rRNA gene amplicon sequences revealed that the bacterial community comprises Nitrospirae (47%), "Parcubacteria" (19%), Deinococcus-Thermus (16%), and Actinobacteria (9%), among others. Notably, only 57 amplicon sequence variants (ASV) were detected, and fifteen of these accounted for 90% of the amplicons. Among the abundant ASVs, an early-branching, uncultivated actinobacterial clade identified as RBG-16-55-12 in the SILVA database was detected. Ten single-cell genomes (average pairwise nucleotide identity: 0.98-1.00; estimated completeness: 33-93%; estimated genome size: ∼2.3 Mb) that affiliated with this clade were obtained. Taxonomic classification using single copy genes indicates that the genomes belong to the actinobacterial class-level clade UBA1414 in the Genome Taxonomy Database. Based on metabolic pathway predictions, these actinobacteria are anaerobes, capable of glycolysis, dissimilatory nitrate reduction and CO2 fixation via the Wood-Ljungdahl (WL) pathway. Several other genomes within UBA1414 and two related class-level clades also encode the WL pathway, which has not yet been reported for the Actinobacteria phylum. For the Hakuba actinobacterium, the energy metabolism related to the WL pathway is likely supported by a combination of the Rnf complex, group 3b and 3d [NiFe]-hydrogenases, [FeFe]-hydrogenases, and V-type (H+/Na+ pump) ATPase. The genomes also harbor a form IV ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) complex, also known as a RubisCO-like protein, and contain signatures of interactions with viruses, including clustered regularly interspaced short palindromic repeat (CRISPR) regions and several phage integrases. This is the first report and detailed genome analysis of a bacterium within the Actinobacteria phylum capable of utilizing the WL pathway. The Hakuba actinobacterium is a member of the clade UBA1414/RBG-16-55-12, formerly within the group "OPB41." We propose to name this bacterium 'Candidatus Hakubanella thermoalkaliphilus.'
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Affiliation(s)
- Nancy Merino
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan.,Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States.,Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
| | - Mikihiko Kawai
- School of Life Sciences and Technology, Tokyo Institute of Technology, Tokyo, Japan.,Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
| | - Eric S Boyd
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, United States
| | - Daniel R Colman
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, United States
| | - Shawn E McGlynn
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan.,Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science, Saitama, Japan.,Blue Marble Space Institute of Science, Seattle, WA, United States
| | - Kenneth H Nealson
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States
| | - Ken Kurokawa
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan.,Department of Informatics, National Institute of Genetics, Shizuoka, Japan
| | - Yuichi Hongoh
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan.,School of Life Sciences and Technology, Tokyo Institute of Technology, Tokyo, Japan
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128
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Martin WF. Older Than Genes: The Acetyl CoA Pathway and Origins. Front Microbiol 2020; 11:817. [PMID: 32655499 PMCID: PMC7325901 DOI: 10.3389/fmicb.2020.00817] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 04/06/2020] [Indexed: 11/13/2022] Open
Abstract
For decades, microbiologists have viewed the acetyl CoA pathway and organisms that use it for H2-dependent carbon and energy metabolism, acetogens and methanogens, as ancient. Classical evidence and newer evidence indicating the antiquity of the acetyl CoA pathway are summarized here. The acetyl CoA pathway requires approximately 10 enzymes, roughly as many organic cofactors, and more than 500 kDa of combined subunit molecular mass to catalyze the conversion of H2 and CO2 to formate, acetate, and pyruvate in acetogens and methanogens. However, a single hydrothermal vent alloy, awaruite (Ni3Fe), can convert H2 and CO2 to formate, acetate, and pyruvate under mild hydrothermal conditions on its own. The chemical reactions of H2 and CO2 to pyruvate thus have a natural tendency to occur without enzymes, given suitable inorganic catalysts. This suggests that the evolution of the enzymatic acetyl CoA pathway was preceded by-and patterned along-a route of naturally occurring exergonic reactions catalyzed by transition metal minerals that could activate H2 and CO2 by chemisorption. The principle of forward (autotrophic) pathway evolution from preexisting non-enzymatic reactions is generalized to the concept of patterned evolution of pathways. In acetogens, exergonic reduction of CO2 by H2 generates acyl phosphates by highly reactive carbonyl groups undergoing attack by inert inorganic phosphate. In that ancient reaction of biochemical energy conservation, the energy behind formation of the acyl phosphate bond resides in the carbonyl, not in phosphate. The antiquity of the acetyl CoA pathway is usually seen in light of CO2 fixation; its role in primordial energy coupling via acyl phosphates and substrate-level phosphorylation is emphasized here.
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Affiliation(s)
- William F. Martin
- Institute for Molecular Evolution, University of Düsseldorf, Düsseldorf, Germany
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129
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Hooks MR, Webster P, Weber JM, Perl S, Barge LM. Effects of Amino Acids on Iron-Silicate Chemical Garden Precipitation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:5793-5801. [PMID: 32421344 DOI: 10.1021/acs.langmuir.0c00502] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Understanding the structure and behavior of chemical gardens is of interest for materials science, for understanding organic-mineral interactions, and for simulating geological mineral structures in hydrothermal systems on Earth and other worlds. Herein, we explored the effects of amino acids on inorganic chemical garden precipitate systems of iron chloride and sodium silicate to determine if/how the addition of organics can affect self-assembling morphologies or crystal growth. Amino acids affect chemical garden growth and morphology at the macro-scale and at the nanoscale. In this reaction system, the concentration of amino acid had a greater impact than the amino acid side chain, and increasing concentrations of organics caused structures to have smoother exteriors as amino acids accumulated on the outside surface. These results provide an example of how organic compounds can become incorporated into and influence the growth of inorganic self-organizing precipitates in far-from-equilibrium systems. Additionally, sample handing methods were developed to successfully image these delicate structures.
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Affiliation(s)
- Michelle R Hooks
- NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States
| | - Paul Webster
- Oak Crest Institute of Science, 132 W Chestnut Ave, Monrovia, California 91016, United States
| | - Jessica M Weber
- NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States
| | - Scott Perl
- NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States
| | - Laura M Barge
- NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, United States
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130
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Zhou Z, Tran PQ, Kieft K, Anantharaman K. Genome diversification in globally distributed novel marine Proteobacteria is linked to environmental adaptation. ISME JOURNAL 2020; 14:2060-2077. [PMID: 32393808 PMCID: PMC7367891 DOI: 10.1038/s41396-020-0669-4] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 04/15/2020] [Accepted: 04/24/2020] [Indexed: 12/14/2022]
Abstract
Proteobacteria constitute one of the most diverse and abundant groups of microbes on Earth. In productive marine environments like deep-sea hydrothermal systems, Proteobacteria are implicated in autotrophy coupled to sulfur, methane, and hydrogen oxidation, sulfate reduction, and denitrification. Beyond chemoautotrophy, little is known about the ecological significance of poorly studied Proteobacteria lineages that are globally distributed and active in hydrothermal systems. Here we apply multi-omics to characterize 51 metagenome-assembled genomes from three hydrothermal vent plumes in the Pacific and Atlantic Oceans that are affiliated with nine Proteobacteria lineages. Metabolic analyses revealed these organisms to contain a diverse functional repertoire including chemolithotrophic ability to utilize sulfur and C1 compounds, and chemoorganotrophic ability to utilize environment-derived fatty acids, aromatics, carbohydrates, and peptides. Comparative genomics with marine and terrestrial microbiomes suggests that lineage-associated functional traits could explain niche specificity. Our results shed light on the ecological functions and metabolic strategies of novel Proteobacteria in hydrothermal systems and beyond, and highlight the relationship between genome diversification and environmental adaptation.
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Affiliation(s)
- Zhichao Zhou
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Patricia Q Tran
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.,Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Kristopher Kieft
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Karthik Anantharaman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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131
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Longo A, Damer B. Factoring Origin of Life Hypotheses into the Search for Life in the Solar System and Beyond. Life (Basel) 2020; 10:E52. [PMID: 32349245 PMCID: PMC7281141 DOI: 10.3390/life10050052] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 04/14/2020] [Accepted: 04/22/2020] [Indexed: 01/13/2023] Open
Abstract
Two widely-cited alternative hypotheses propose geological localities and biochemical mechanisms for life's origins. The first states that chemical energy available in submarine hydrothermal vents supported the formation of organic compounds and initiated primitive metabolic pathways which became incorporated in the earliest cells; the second proposes that protocells self-assembled from exogenous and geothermally-delivered monomers in freshwater hot springs. These alternative hypotheses are relevant to the fossil record of early life on Earth, and can be factored into the search for life elsewhere in the Solar System. This review summarizes the evidence supporting and challenging these hypotheses, and considers their implications for the search for life on various habitable worlds. It will discuss the relative probability that life could have emerged in environments on early Mars, on the icy moons of Jupiter and Saturn, and also the degree to which prebiotic chemistry could have advanced on Titan. These environments will be compared to ancient and modern terrestrial analogs to assess their habitability and biopreservation potential. Origins of life approaches can guide the biosignature detection strategies of the next generation of planetary science missions, which could in turn advance one or both of the leading alternative abiogenesis hypotheses.
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Affiliation(s)
- Alex Longo
- National Aeronautics and Space Administration Headquarters, Washington, DC 20546, USA
- Department of Geology, The University of North Carolina, Chapel Hill, NC 27599, USA
| | - Bruce Damer
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064, USA or
- Digital Space Research, Boulder Creek, CA 95006, USA
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132
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Bartlett S, Wong ML. Defining Lyfe in the Universe: From Three Privileged Functions to Four Pillars. Life (Basel) 2020; 10:E42. [PMID: 32316364 PMCID: PMC7235751 DOI: 10.3390/life10040042] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/12/2020] [Accepted: 04/13/2020] [Indexed: 01/08/2023] Open
Abstract
Motivated by the need to paint a more general picture of what life is-and could be-with respect to the rest of the phenomena of the universe, we propose a new vocabulary for astrobiological research. Lyfe is defined as any system that fulfills all four processes of the living state, namely: dissipation, autocatalysis, homeostasis, and learning. Life is defined as the instance of lyfe that we are familiar with on Earth, one that uses a specific organometallic molecular toolbox to record information about its environment and achieve dynamical order by dissipating certain planetary disequilibria. This new classification system allows the astrobiological community to more clearly define the questions that propel their research-e.g., whether they are developing a historical narrative to explain the origin of life (on Earth), or a universal narrative for the emergence of lyfe, or whether they are seeking signs of life specifically, or lyfe at large across the universe. While the concept of "life as we don't know it" is not new, the four pillars of lyfe offer a novel perspective on the living state that is indifferent to the particular components that might produce it.
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Affiliation(s)
- Stuart Bartlett
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Michael L. Wong
- Department of Astronomy and Astrobiology Program, University of Washington, Seattle, WA 98195, USA;
- NASA Nexus for Exoplanet System Science’s Virtual Planetary Laboratory, University of Washington, Seattle, WA 98195, USA
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133
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Damer B, Deamer D. The Hot Spring Hypothesis for an Origin of Life. ASTROBIOLOGY 2020; 20:429-452. [PMID: 31841362 PMCID: PMC7133448 DOI: 10.1089/ast.2019.2045] [Citation(s) in RCA: 178] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 10/23/2019] [Indexed: 05/05/2023]
Abstract
We present a testable hypothesis related to an origin of life on land in which fluctuating volcanic hot spring pools play a central role. The hypothesis is based on experimental evidence that lipid-encapsulated polymers can be synthesized by cycles of hydration and dehydration to form protocells. Drawing on metaphors from the bootstrapping of a simple computer operating system, we show how protocells cycling through wet, dry, and moist phases will subject polymers to combinatorial selection and draw structural and catalytic functions out of initially random sequences, including structural stabilization, pore formation, and primitive metabolic activity. We propose that protocells aggregating into a hydrogel in the intermediate moist phase of wet-dry cycles represent a primitive progenote system. Progenote populations can undergo selection and distribution, construct niches in new environments, and enable a sharing network effect that can collectively evolve them into the first microbial communities. Laboratory and field experiments testing the first steps of the scenario are summarized. The scenario is then placed in a geological setting on the early Earth to suggest a plausible pathway from life's origin in chemically optimal freshwater hot spring pools to the emergence of microbial communities tolerant to more extreme conditions in dilute lakes and salty conditions in marine environments. A continuity is observed for biogenesis beginning with simple protocell aggregates, through the transitional form of the progenote, to robust microbial mats that leave the fossil imprints of stromatolites so representative in the rock record. A roadmap to future testing of the hypothesis is presented. We compare the oceanic vent with land-based pool scenarios for an origin of life and explore their implications for subsequent evolution to multicellular life such as plants. We conclude by utilizing the hypothesis to posit where life might also have emerged in habitats such as Mars or Saturn's icy moon Enceladus. "To postulate one fortuitously catalyzed reaction, perhaps catalyzed by a metal ion, might be reasonable, but to postulate a suite of them is to appeal to magic." -Leslie Orgel.
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Affiliation(s)
- Bruce Damer
- Department of Biomolecular Engineering, University of California, Santa Cruz, California
| | - David Deamer
- Department of Biomolecular Engineering, University of California, Santa Cruz, California
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134
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Xavier JC, Hordijk W, Kauffman S, Steel M, Martin WF. Autocatalytic chemical networks at the origin of metabolism. Proc Biol Sci 2020; 287:20192377. [PMID: 32156207 PMCID: PMC7126077 DOI: 10.1098/rspb.2019.2377] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 02/12/2020] [Indexed: 12/12/2022] Open
Abstract
Modern cells embody metabolic networks containing thousands of elements and form autocatalytic sets of molecules that produce copies of themselves. How the first self-sustaining metabolic networks arose at life's origin is a major open question. Autocatalytic sets smaller than metabolic networks were proposed as transitory intermediates at the origin of life, but evidence for their role in prebiotic evolution is lacking. Here, we identify reflexively autocatalytic food-generated networks (RAFs)-self-sustaining networks that collectively catalyse all their reactions-embedded within microbial metabolism. RAFs in the metabolism of ancient anaerobic autotrophs that live from H2 and CO2 provided with small-molecule catalysts generate acetyl-CoA as well as amino acids and bases, the monomeric components of protein and RNA, but amino acids and bases without organic catalysts do not generate metabolic RAFs. This suggests that RAFs identify attributes of biochemical origins conserved in metabolic networks. RAFs are consistent with an autotrophic origin of metabolism and furthermore indicate that autocatalytic chemical networks preceded proteins and RNA in evolution. RAFs uncover intermediate stages in the emergence of metabolic networks, narrowing the gaps between early Earth chemistry and life.
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Affiliation(s)
- Joana C. Xavier
- Institut für Molekulare Evolution, Heinrich Heine Universität, 40225 Düsseldorf, Germany
| | - Wim Hordijk
- Konrad Lorenz Institute for Evolution and Cognition Research, 3400 Klosterneuburg, Austria
| | | | - Mike Steel
- Biomathematics Research Centre, University of Canterbury, Christchurch 8041, New Zealand
| | - William F. Martin
- Institut für Molekulare Evolution, Heinrich Heine Universität, 40225 Düsseldorf, Germany
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
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135
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A hydrogen-dependent geochemical analogue of primordial carbon and energy metabolism. Nat Ecol Evol 2020; 4:534-542. [PMID: 32123322 DOI: 10.1038/s41559-020-1125-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 01/23/2020] [Indexed: 11/08/2022]
Abstract
Hydrogen gas, H2, is generated by alkaline hydrothermal vents through an ancient geochemical process called serpentinization, in which water reacts with iron-containing minerals deep within the Earth's crust. H2 is the electron donor for the most ancient and the only energy-releasing route of biological CO2 fixation, the acetyl-CoA pathway. At the origin of metabolism, CO2 fixation by hydrothermal H2 within serpentinizing systems could have preceded and patterned biotic pathways. Here we show that three hydrothermal minerals-greigite (Fe3S4), magnetite (Fe3O4) and awaruite (Ni3Fe)-catalyse the fixation of CO2 with H2 at 100 °C under alkaline aqueous conditions. The product spectrum includes formate (up to 200 mM), acetate (up to 100 µM), pyruvate (up to 10 µM), methanol (up to 100 µM) and methane. The results shed light on both the geochemical origin of microbial metabolism and the nature of abiotic formate and methane synthesis in modern hydrothermal vents.
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136
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White LM, Shibuya T, Vance SD, Christensen LE, Bhartia R, Kidd R, Hoffmann A, Stucky GD, Kanik I, Russell MJ. Simulating Serpentinization as It Could Apply to the Emergence of Life Using the JPL Hydrothermal Reactor. ASTROBIOLOGY 2020; 20:307-326. [PMID: 32125196 DOI: 10.1089/ast.2018.1949] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The molecules feeding life's emergence are thought to have been provided through the hydrothermal interactions of convecting carbonic ocean waters with minerals comprising the early Hadean oceanic crust. Few laboratory experiments have simulated ancient hydrothermal conditions to test this conjecture. We used the JPL hydrothermal flow reactor to investigate CO2 reduction in simulated ancient alkaline convective systems over 3 days (T = 120°C, P = 100 bar, pH = 11). H2-rich hydrothermal simulant and CO2-rich ocean simulant solutions were periodically driven in 4-h cycles through synthetic mafic and ultramafic substrates and Fe>Ni sulfides. The resulting reductants included micromoles of HS- and formate accompanied possibly by micromoles of acetate and intermittent minor bursts of methane as ascertained by isotopic labeling. The formate concentrations directly correlated with the CO2 input as well as with millimoles of Mg2+ ions, whereas the acetate did not. Also, tens of micromoles of methane were drawn continuously from the reactor materials during what appeared to be the onset of serpentinization. These results support the hypothesis that formate may have been delivered directly to a branch of an emerging acetyl coenzyme-A pathway, thus obviating the need for the very first hydrogenation of CO2 to be made in a hydrothermal mound. Another feed to early metabolism could have been methane, likely mostly leached from primary CH4 present in the original Hadean crust or emanating from the mantle. That a small volume of methane was produced sporadically from the 13CO2-feed, perhaps from transient occlusions, echoes the mixed results and interpretations from other laboratories. As serpentinization and hydrothermal leaching can occur wherever an ocean convects within anhydrous olivine- and sulfide-rich crust, these results may be generalized to other wet rocky planets and moons in our solar system and beyond.
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Affiliation(s)
- Lauren M White
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California
- Project Systems Engineering, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Takazo Shibuya
- Department of Subsurface Geobiological Analysis and Research (D-SUGAR), Project Team for Development of New-generation Research Protocol for Submarine Resources, and Research and Development (RandD), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
- Research and Development (RandD) Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Steven D Vance
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Lance E Christensen
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Rohit Bhartia
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Richard Kidd
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Adam Hoffmann
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Galen D Stucky
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California
- Materials Department, University of California at Santa Barbara, Santa Barbara, California
| | - Isik Kanik
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Michael J Russell
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
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137
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Preiner M, Asche S, Becker S, Betts HC, Boniface A, Camprubi E, Chandru K, Erastova V, Garg SG, Khawaja N, Kostyrka G, Machné R, Moggioli G, Muchowska KB, Neukirchen S, Peter B, Pichlhöfer E, Radványi Á, Rossetto D, Salditt A, Schmelling NM, Sousa FL, Tria FDK, Vörös D, Xavier JC. The Future of Origin of Life Research: Bridging Decades-Old Divisions. Life (Basel) 2020; 10:E20. [PMID: 32110893 PMCID: PMC7151616 DOI: 10.3390/life10030020] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 02/19/2020] [Accepted: 02/21/2020] [Indexed: 12/12/2022] Open
Abstract
Research on the origin of life is highly heterogeneous. After a peculiar historical development, it still includes strongly opposed views which potentially hinder progress. In the 1st Interdisciplinary Origin of Life Meeting, early-career researchers gathered to explore the commonalities between theories and approaches, critical divergence points, and expectations for the future. We find that even though classical approaches and theories-e.g. bottom-up and top-down, RNA world vs. metabolism-first-have been prevalent in origin of life research, they are ceasing to be mutually exclusive and they can and should feed integrating approaches. Here we focus on pressing questions and recent developments that bridge the classical disciplines and approaches, and highlight expectations for future endeavours in origin of life research.
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Affiliation(s)
- Martina Preiner
- Institute of Molecular Evolution, University of Düsseldorf, 40225 Düsseldorf, Germany; (S.G.G.); (F.D.K.T.)
| | - Silke Asche
- School of Chemistry, University of Glasgow, Glasgow G128QQ, UK;
| | - Sidney Becker
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK;
| | - Holly C. Betts
- School of Earth Sciences, University of Bristol, Bristol BS8 1RL, UK;
| | - Adrien Boniface
- Environmental Microbial Genomics, Laboratoire Ampère, Ecole Centrale de Lyon, Université de Lyon, 69130 Ecully, France;
| | - Eloi Camprubi
- Origins Center, Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, The Netherlands;
| | - Kuhan Chandru
- Space Science Center (ANGKASA), Institute of Climate Change, Level 3, Research Complex, National University of Malaysia, UKM Bangi 43600, Selangor, Malaysia;
- Department of Physical Chemistry, University of Chemistry and Technology, Prague, Technicka 5, 16628 Prague 6–Dejvice, Czech Republic
| | - Valentina Erastova
- UK Centre for Astrobiology, School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, UK;
| | - Sriram G. Garg
- Institute of Molecular Evolution, University of Düsseldorf, 40225 Düsseldorf, Germany; (S.G.G.); (F.D.K.T.)
| | - Nozair Khawaja
- Institut für Geologische Wissenschaften, Freie Universität Berlin, 12249 Berlin, Germany;
| | | | - Rainer Machné
- Institute of Synthetic Microbiology, University of Düsseldorf, 40225 Düsseldorf, Germany; (R.M.); (N.M.S.)
- Quantitative and Theoretical Biology, University of Düsseldorf, 40225 Düsseldorf, Germany
| | - Giacomo Moggioli
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4DQ, UK;
| | - Kamila B. Muchowska
- Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, 67000 Strasbourg, France;
| | - Sinje Neukirchen
- Archaea Biology and Ecogenomics Division, University of Vienna, 1090 Vienna, Austria; (S.N.); (E.P.); (F.L.S.)
| | - Benedikt Peter
- Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany;
| | - Edith Pichlhöfer
- Archaea Biology and Ecogenomics Division, University of Vienna, 1090 Vienna, Austria; (S.N.); (E.P.); (F.L.S.)
| | - Ádám Radványi
- Department of Plant Systematics, Ecology and Theoretical Biology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary (D.V.)
- Institute of Evolution, MTA Centre for Ecological Research, Klebelsberg Kuno u. 3., H-8237 Tihany, Hungary
| | - Daniele Rossetto
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, 38123 Trento, Italy;
| | - Annalena Salditt
- Systems Biophysics, Physics Department, Ludwig-Maximilians-Universität München, 80799 Munich, Germany;
| | - Nicolas M. Schmelling
- Institute of Synthetic Microbiology, University of Düsseldorf, 40225 Düsseldorf, Germany; (R.M.); (N.M.S.)
- Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, 50674 Cologne, Germany
| | - Filipa L. Sousa
- Archaea Biology and Ecogenomics Division, University of Vienna, 1090 Vienna, Austria; (S.N.); (E.P.); (F.L.S.)
| | - Fernando D. K. Tria
- Institute of Molecular Evolution, University of Düsseldorf, 40225 Düsseldorf, Germany; (S.G.G.); (F.D.K.T.)
| | - Dániel Vörös
- Department of Plant Systematics, Ecology and Theoretical Biology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary (D.V.)
- Institute of Evolution, MTA Centre for Ecological Research, Klebelsberg Kuno u. 3., H-8237 Tihany, Hungary
| | - Joana C. Xavier
- Institute of Molecular Evolution, University of Düsseldorf, 40225 Düsseldorf, Germany; (S.G.G.); (F.D.K.T.)
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138
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Lang SQ, Brazelton WJ. Habitability of the marine serpentinite subsurface: a case study of the Lost City hydrothermal field. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20180429. [PMID: 31902336 PMCID: PMC7015304 DOI: 10.1098/rsta.2018.0429] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
The Lost City hydrothermal field is a dramatic example of the biological potential of serpentinization. Microbial life is prevalent throughout the Lost City chimneys, powered by the hydrogen gas and organic molecules produced by serpentinization and its associated geochemical reactions. Microbial life in the serpentinite subsurface below the Lost City chimneys, however, is unlikely to be as dense or active. The marine serpentinite subsurface poses serious challenges for microbial activity, including low porosities, the combination of stressors of elevated temperature, high pH and a lack of bioavailable ∑CO2. A better understanding of the biological opportunities and challenges in serpentinizing systems would provide important insights into the total habitable volume of Earth's crust and for the potential of the origin and persistence of life in Earth's subsurface environments. Furthermore, the limitations to life in serpentinizing subsurface environments on Earth have significant implications for the habitability of subsurface environments on ocean worlds such as Europa and Enceladus. Here, we review the requirements and limitations of life in serpentinizing systems, informed by our research at the Lost City and the underwater mountain on which it resides, the Atlantis Massif. This article is part of a discussion meeting issue 'Serpentinite in the Earth System'.
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Affiliation(s)
- Susan Q. Lang
- School of the Earth, Ocean, and Environment, University of South Carolina, Columbia, SC 29208, USA
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139
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Mayhew LE, Ellison ET. A synthesis and meta-analysis of the Fe chemistry of serpentinites and serpentine minerals. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20180420. [PMID: 31902340 PMCID: PMC7015306 DOI: 10.1098/rsta.2018.0420] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/18/2019] [Indexed: 06/10/2023]
Abstract
The iron chemistry of serpentinites and serpentine group minerals is often invoked as a record of the setting and conditions of serpentinization because Fe behaviour is influenced by reaction conditions. Iron can be partitioned into a variety of secondary mineral phases and undergo variable extents of oxidation and/or reduction during serpentinization. This behaviour influences geophysical, geochemical and biological aspects of serpentinizing systems and, more broadly, earth systems. Iron chemistry of serpentinites and serpentines is frequently analysed and reported for single systems. Interpretations of the controls on, and the implications of, Fe behaviour drawn from a single system are often widely extrapolated. There is a wealth of serpentinite/serpentine chemical composition data available in the literature. Consequently, compilation of a database including potential predictors of Fe behaviour and measures of Fe chemistry enables systematic investigation of trends in Fe behaviour across a variety of systems and conditions. The database presented here contains approximately 2000 individual data points including both bulk rock and serpentine mineral geochemical data which are paired whenever possible. Measures of total Fe and Fe oxidation state, which are more limited, are compiled with characteristics of the systems from which they were sampled. Observations of trends in Fe chemistry in serpentinites and serpentines across the variety of geologic systems and parameters will aid in verifying and strengthening interpretations made on the basis of Fe chemistry. This article is part of a discussion meeting issue 'Serpentinite in the Earth system'.
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140
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Bains W. Getting Beyond the Toy Domain. Meditations on David Deamer's "Assembling Life". Life (Basel) 2020; 10:life10020018. [PMID: 32085425 PMCID: PMC7175206 DOI: 10.3390/life10020018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 02/09/2020] [Accepted: 02/15/2020] [Indexed: 11/16/2022] Open
Abstract
David Deamer has written another book, Assembling Life, on the origin of life. It is unapologetically polemic, presenting Deamer's view that life originated in fresh water hydrothermal fields on volcanic islands on early Earth, arguing that this provided a unique environment not just for organic chemistry but for the self-assembling structure that drive that chemistry and form the basis of structure in life. It is worth reading, it is an advance in the field, but is it convincing? I argue that the Origin of Life field as a whole is unconvincing, generating results in Toy Domains that cannot be scaled to any real world scenario. I suggest that, by analogy with the history of artificial intelligence and solar astronomy, we need much more scale, and fundamentally new ideas, to take the field forward.
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Affiliation(s)
- William Bains
- Five Alarm Bio Ltd., O2h Scitech Park, Mill Lane, Hauxton, Cambridge CB22 5HX, UK;
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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141
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Black AJ, Bourrat P, Rainey PB. Ecological scaffolding and the evolution of individuality. Nat Ecol Evol 2020; 4:426-436. [PMID: 32042121 DOI: 10.1038/s41559-019-1086-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 12/17/2019] [Indexed: 12/21/2022]
Abstract
Evolutionary transitions in individuality are central to the emergence of biological complexity. Recent experiments provide glimpses of processes underpinning the transition from single cells to multicellular life and draw attention to the critical role of ecology. Here, we emphasize this ecological dimension and argue that its current absence from theoretical frameworks hampers development of general explanatory solutions. Using mechanistic mathematical models, we show how a minimal ecological structure comprising patchily distributed resources and between-patch dispersal can scaffold Darwinian-like properties on collectives of cells. This scaffolding causes cells to participate directly in the process of evolution by natural selection as if they were members of multicellular collectives, with collectives participating in a death-birth process arising from the interplay between the timing of dispersal events and the rate of resource use by cells. When this timescale is sufficiently long and new collectives are founded by single cells, collectives experience conditions that favour evolution of a reproductive division of labour. Together our simple model makes explicit key events in the major evolutionary transition to multicellularity. It also makes predictions concerning the life history of certain pathogens and serves as an ecological recipe for experimental realization of evolutionary transitions.
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Affiliation(s)
- Andrew J Black
- School of Mathematical Sciences, University of Adelaide, Adelaide, South Australia, Australia.
| | - Pierrick Bourrat
- Department of Philosophy, Macquarie University, Sydney, New South Wales, Australia.,Department of Philosophy & Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Paul B Rainey
- Department of Microbial Population Biology, Max Planck Institute for Evolutionary Biology, Plön, Germany. .,Laboratoire de Génétique de l'Evolution, Chemistry, Biology and Innovation (CBI) UMR8231, ESPCI Paris, CNRS, PSL Research University, Paris, France.
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142
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Cornish-Bowden A, Cárdenas ML. Contrasting theories of life: Historical context, current theories. In search of an ideal theory. Biosystems 2020; 188:104063. [DOI: 10.1016/j.biosystems.2019.104063] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 10/10/2019] [Accepted: 10/10/2019] [Indexed: 12/18/2022]
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143
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Taubner RS, Olsson-Francis K, Vance SD, Ramkissoon NK, Postberg F, de Vera JP, Antunes A, Camprubi Casas E, Sekine Y, Noack L, Barge L, Goodman J, Jebbar M, Journaux B, Karatekin Ö, Klenner F, Rabbow E, Rettberg P, Rückriemen-Bez T, Saur J, Shibuya T, Soderlund KM. Experimental and Simulation Efforts in the Astrobiological Exploration of Exooceans. SPACE SCIENCE REVIEWS 2020; 216:9. [PMID: 32025060 PMCID: PMC6977147 DOI: 10.1007/s11214-020-0635-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 01/06/2020] [Indexed: 05/05/2023]
Abstract
The icy satellites of Jupiter and Saturn are perhaps the most promising places in the Solar System regarding habitability. However, the potential habitable environments are hidden underneath km-thick ice shells. The discovery of Enceladus' plume by the Cassini mission has provided vital clues in our understanding of the processes occurring within the interior of exooceans. To interpret these data and to help configure instruments for future missions, controlled laboratory experiments and simulations are needed. This review aims to bring together studies and experimental designs from various scientific fields currently investigating the icy moons, including planetary sciences, chemistry, (micro-)biology, geology, glaciology, etc. This chapter provides an overview of successful in situ, in silico, and in vitro experiments, which explore different regions of interest on icy moons, i.e. a potential plume, surface, icy shell, water and brines, hydrothermal vents, and the rocky core.
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Affiliation(s)
- Ruth-Sophie Taubner
- Archaea Biology and Ecogenomics Division, University of Vienna, Vienna, Austria
| | | | | | | | | | | | - André Antunes
- State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau SAR, China
| | | | | | - Lena Noack
- Freie Universität Berlin, Berlin, Germany
| | | | | | | | | | | | | | - Elke Rabbow
- German Aerospace Center (DLR), Cologne, Germany
| | | | | | | | - Takazo Shibuya
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
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144
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Jordan SF, Nee E, Lane N. Isoprenoids enhance the stability of fatty acid membranes at the emergence of life potentially leading to an early lipid divide. Interface Focus 2019; 9:20190067. [PMID: 31641436 PMCID: PMC6802135 DOI: 10.1098/rsfs.2019.0067] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 08/29/2019] [Indexed: 01/05/2023] Open
Abstract
Two key problems concern cell membranes during the emergence and early evolution of life: what was their initial composition, and why did the membranes of archaea and bacteria diverge? The composition of the first cell membranes could shed light on the most likely environment for the emergence of life. The opposing stereochemistry of modern lipid glycerol-phosphate headgroups in bacteria and archaea suggests that early membranes were composed of single chain amphiphiles, perhaps both fatty acids and isoprenoids. We investigated the effect of adding isoprenoids to fatty acid membranes using a combination of UV-visible spectroscopy, confocal microscopy and transmission electron microscopy. We tested the stability of these membranes across a pH range and under different concentrations of ionic species relevant to oceanic hydrothermal environments, including Na2+, Cl-, Mg2+, Ca2+, HC O 3 - , Fe3+, Fe2+ and S2-. We also tested the assembly of vesicles in the presence of Fe particles and FeS precipitates. We found that isoprenoids enhance the stability of membranes in the presence of salts but require 30-fold higher concentrations for membrane formation. Intriguingly, isoprenoids strongly inhibit the tendency of vesicles to aggregate together in the presence of either Fe particles or FeS precipitates. These striking physical differences in the stability and aggregation of protocells may have shaped the divergence of bacteria and archaea in early hydrothermal environments.
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Affiliation(s)
- Sean F. Jordan
- Centre for Life's Origin and Evolution, Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
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145
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Abstract
Books with titles like 'The Call of the Wild' seemed to set a path for a life. Thus, I would be an explorer-a plan that did not work out so well, at least at first. On leaving school I got a job as a 'Works Chemist Improver', testing Ni catalysts for the hydrogenation of phenol to cyclohexanol. Taking night classes I passed enough exams to study geology at Queen Mary College, London. Armed thus I travelled to the Solomon Islands where geology is a 'happening'! Next was Canada to visit a mine sunk into a 1.5 billion year old Pb-Zn orebody precipitated from submarine hot springs. At last I reached the Yukon to prospect for silver. Thence to Ireland researching what I also took to be 'exhalative' (i.e. hot spring-related) Pb-Zn orebodies. While there in 1979, the discovery of 350°C metal-bearing acidic waters issuing from submarine Black Smoker chimneys in the Pacific sent us searching for fossil examples in the Irish mines. However, the chimneys we found were more like chemical gardens than Black Smokers, a finding that made us think about the emergence of life. After all, what better for life's emergence than to have a membrane comprising Fe minerals dosed with Ni in our chimneys to mediate the 'hydrogenation' of CO2-life's job anyway. Indeed, such a membrane would keep redox and pH disequilibria at bay, just like biological membranes. At the same time, my field research among Alpine ophiolites-ocean floor mafic rocks obducted to the Alps-indicated that alkaline waters bearing H2 and CH4 were a result of serpentinization, a process that must have operated in all ocean floors over all time. Thus it was that we could predict the Lost City hydrothermal field 10 years before its discovery in the North Atlantic in the year 2000. Lost City comprises a number of alkaline springs at up to 90°C that produce carbonate and brucite (Mg[OH]2) chimneys. We had surmised that Ni-enriched FeS chimneys would have precipitated at comparable alkaline springs issuing into a metal-rich carbonic ocean on the very early Earth (inducing membrane potentials comparable to those capable of succouring all life, and presumably, sufficient to drive life into being). However, our laboratory precipitates also revealed green rust, thought to be the precursor to the magnetite now comprising the Archaean Banded Iron Formations. We now look upon green rust, also known as fougèrite, as the tangible, base fractal of life.
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Affiliation(s)
- Michael J. Russell
- NASA Astrobiology Institute, NASA Ames Research Center, Moffett Field, CA, USA
- http://bip.cnrs-mrs.fr/bip09/AHVics.html
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146
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Vasiliadou R, Dimov N, Szita N, Jordan SF, Lane N. Possible mechanisms of CO 2 reduction by H 2 via prebiotic vectorial electrochemistry. Interface Focus 2019; 9:20190073. [PMID: 31641439 PMCID: PMC6802132 DOI: 10.1098/rsfs.2019.0073] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2019] [Indexed: 02/07/2023] Open
Abstract
Methanogens are putatively ancestral autotrophs that reduce CO2 with H2 to form biomass using a membrane-bound, proton-motive Fe(Ni)S protein called the energy-converting hydrogenase (Ech). At the origin of life, geologically sustained H+ gradients across inorganic barriers containing Fe(Ni)S minerals could theoretically have driven CO2 reduction by H2 through vectorial chemistry in a similar way to Ech. pH modulation of the redox potentials of H2, CO2 and Fe(Ni)S minerals could in principle enable an otherwise endergonic reaction. Here, we analyse whether vectorial electrochemistry can facilitate the reduction of CO2 by H2 under alkaline hydrothermal conditions using a microfluidic reactor. We present pilot data showing that steep pH gradients of approximately 5 pH units can be sustained over greater than 5 h across Fe(Ni)S barriers, with H+-flux across the barrier about two million-fold faster than OH--flux. This high flux produces a calculated 3-pH unit-gradient (equating to 180 mV) across single approximately 25-nm Fe(Ni)S nanocrystals, which is close to that required to reduce CO2. However, the poor solubility of H2 at atmospheric pressure limits CO2 reduction by H2, explaining why organic synthesis has so far proved elusive in our reactor. Higher H2 concentration will be needed in future to facilitate CO2 reduction through prebiotic vectorial electrochemistry.
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Affiliation(s)
- Rafaela Vasiliadou
- Centre for Life's Origin and Evolution, Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Nikolay Dimov
- School of Engineering and Computer Science, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
| | - Nicolas Szita
- Department of Biochemical Engineering, University College London, Bernard Katz Building, Gower Street, London WC1E 6BT, UK
| | - Sean F. Jordan
- Centre for Life's Origin and Evolution, Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Nick Lane
- Centre for Life's Origin and Evolution, Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
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147
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Abstract
Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much stronger carbon-isotope fractionation occurs, however, during methanogenesis, whereby methane is depleted in 13C and, by mass balance, DIC is enriched in 13C, such that isotopic distributions are predominantly influenced by microbial metabolisms involving methane. Methane metabolisms are essentially mediated through a single enzymatic pathway in both Archaea and Bacteria, the Wood–Ljungdahl (WL) pathway, but it remains unclear where in the pathway carbon-isotope fractionation occurs. While it is generally assumed that fractionation arises from kinetic effects of enzymatic reactions, it has recently been suggested that partial carbon-isotope equilibration occurs within the pathway of anaerobic methane oxidation. Equilibrium fractionation might also occur during methanogenesis, as the isotopic difference between DIC and methane is commonly on the order of 75‰, which is near the thermodynamic equilibrium. The isotopic signature in DIC and methane highly varies in marine porewaters, reflecting the distribution of different microbial metabolisms contributing to DIC. If carbon isotopes are preserved in diagenetic carbonates, they may provide a powerful biosignature for the conditions in the deep biosphere, specifically in proximity to the sulphate–methane transition zone. Large variations in isotopic signatures in diagenetic archives have been found that document dramatic changes in sub-seafloor biosphere activity over geological time scales. We present a brief overview on carbon isotopes, including microbial fractionation mechanisms, transport effects, preservation in diagenetic carbonate archives, and their implications for the past sub-seafloor biosphere and its role in the global carbon cycle. We discuss open questions and future potentials of carbon isotopes as archives to trace the deep biosphere through time.
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148
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Deamer D, Damer B, Kompanichenko V. Hydrothermal Chemistry and the Origin of Cellular Life. ASTROBIOLOGY 2019; 19:1523-1537. [PMID: 31596608 DOI: 10.1089/ast.2018.1979] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two processes required for life's origin are condensation reactions that produce essential biopolymers by a nonenzymatic reaction, and self-assembly of membranous compartments that encapsulate the polymers into populations of protocells. Because life today thrives not just in the temperate ocean and lakes but also in extreme conditions of temperature, salinity, and pH, there is a general assumption that any form of liquid water would be sufficient to support the origin of life as long as there are sources of chemical energy and simple organic compounds. We argue here that the first forms of life would be physically and chemically fragile and would be strongly affected by ionic solutes and pH. A hypothesis emerges from this statement that hot springs associated with volcanic land masses have an ionic composition more conducive to self-assembly and polymerization than seawater. Here we have compared the ionic solutes of seawater with those of terrestrial hot springs. We then describe preliminary experimental results that show how the hypothesis can be tested in a prebiotic analog environment.
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Affiliation(s)
- David Deamer
- Department of Biomolecular Engineering, University of California, Santa Cruz, California
| | - Bruce Damer
- Department of Biomolecular Engineering, University of California, Santa Cruz, California
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149
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Goldford JE, Hartman H, Marsland R, Segrè D. Environmental boundary conditions for the origin of life converge to an organo-sulfur metabolism. Nat Ecol Evol 2019; 3:1715-1724. [PMID: 31712697 PMCID: PMC6881557 DOI: 10.1038/s41559-019-1018-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 09/27/2019] [Indexed: 11/30/2022]
Abstract
It has been suggested that a deep memory of early life is hidden in the architecture of metabolic networks, whose reactions could have been catalyzed by small molecules or minerals before genetically encoded enzymes. A major challenge in unravelling these early steps is assessing the plausibility of a connected, thermodynamically consistent proto-metabolism under different geochemical conditions, which are still surrounded by high uncertainty. Here we combine network-based algorithms with physico-chemical constraints on chemical reaction networks to systematically show how different combinations of parameters (temperature, pH, redox potential and availability of molecular precursors) could have affected the evolution of a proto-metabolism. Our analysis of possible trajectories indicates that a subset of boundary conditions converges to an organo-sulfur-based proto-metabolic network fuelled by a thioester- and redox-driven variant of the reductive tricarboxylic acid cycle that is capable of producing lipids and keto acids. Surprisingly, environmental sources of fixed nitrogen and low-potential electron donors are not necessary for the earliest phases of biochemical evolution. We use one of these networks to build a steady-state dynamical metabolic model of a protocell, and find that different combinations of carbon sources and electron donors can support the continuous production of a minimal ancient 'biomass' composed of putative early biopolymers and fatty acids.
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Affiliation(s)
- Joshua E Goldford
- Bioinformatics Program, Boston University, Boston, MA, USA.
- Department of Chemistry, Boston University, Boston, MA, USA.
- Biological Design Center, Boston University, Boston, MA, USA.
| | - Hyman Hartman
- Earth, Atmosphere and Planetary Science Department, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | - Daniel Segrè
- Bioinformatics Program, Boston University, Boston, MA, USA.
- Biological Design Center, Boston University, Boston, MA, USA.
- Department of Physics, Boston University, Boston, MA, USA.
- Department of Biomedical Engineering, Department of Biology, Boston University, Boston, MA, USA.
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150
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Promotion of protocell self-assembly from mixed amphiphiles at the origin of life. Nat Ecol Evol 2019; 3:1705-1714. [PMID: 31686020 DOI: 10.1038/s41559-019-1015-y] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 09/25/2019] [Indexed: 01/01/2023]
Abstract
Vesicles formed from single-chain amphiphiles (SCAs) such as fatty acids probably played an important role in the origin of life. A major criticism of the hypothesis that life arose in an early ocean hydrothermal environment is that hot temperatures, large pH gradients, high salinity and abundant divalent cations should preclude vesicle formation. However, these arguments are based on model vesicles using 1-3 SCAs, even though Fischer-Tropsch-type synthesis under hydrothermal conditions produces a wide array of fatty acids and 1-alkanols, including abundant C10-C15 compounds. Here, we show that mixtures of these C10-C15 SCAs form vesicles in aqueous solutions between pH ~6.5 and >12 at modern seawater concentrations of NaCl, Mg2+ and Ca2+. Adding C10 isoprenoids improves vesicle stability even further. Vesicles form most readily at temperatures of ~70 °C and require salinity and strongly alkaline conditions to self-assemble. Thus, alkaline hydrothermal conditions not only permit protocell formation at the origin of life but actively favour it.
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