1
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Garcia AK, Kędzior M, Taton A, Li M, Young JN, Kaçar B. Effects of RuBisCO and CO 2 concentration on cyanobacterial growth and carbon isotope fractionation. GEOBIOLOGY 2023; 21:390-403. [PMID: 36602111 DOI: 10.1111/gbi.12543] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 11/11/2022] [Accepted: 12/19/2022] [Indexed: 06/17/2023]
Abstract
Carbon isotope biosignatures preserved in the Precambrian geologic record are primarily interpreted to reflect ancient cyanobacterial carbon fixation catalyzed by Form I RuBisCO enzymes. The average range of isotopic biosignatures generally follows that produced by extant cyanobacteria. However, this observation is difficult to reconcile with several environmental (e.g., temperature, pH, and CO2 concentrations), molecular, and physiological factors that likely would have differed during the Precambrian and can produce fractionation variability in contemporary organisms that meets or exceeds that observed in the geologic record. To test a specific range of genetic and environmental factors that may impact ancient carbon isotope biosignatures, we engineered a mutant strain of the model cyanobacterium Synechococcus elongatus PCC 7942 that overexpresses RuBisCO across varying atmospheric CO2 concentrations. We hypothesized that changes in RuBisCO expression would impact the net rates of intracellular CO2 fixation versus CO2 supply, and thus whole-cell carbon isotope discrimination. In particular, we investigated the impacts of RuBisCO overexpression under changing CO2 concentrations on both carbon isotope biosignatures and cyanobacterial physiology, including cell growth and oxygen evolution rates. We found that an increased pool of active RuBisCO does not significantly affect the 13 C/12 C isotopic discrimination (εp ) at all tested CO2 concentrations, yielding εp of ≈ 23‰ for both wild-type and mutant strains at elevated CO2 . We therefore suggest that expected variation in cyanobacterial RuBisCO expression patterns should not confound carbon isotope biosignature interpretation. A deeper understanding of environmental, evolutionary, and intracellular factors that impact cyanobacterial physiology and isotope discrimination is crucial for reconciling microbially driven carbon biosignatures with those preserved in the geologic record.
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Affiliation(s)
- Amanda K Garcia
- Department of Bacteriology, University of Wisconsin - Madison, Madison, Wisconsin, USA
| | - Mateusz Kędzior
- Department of Bacteriology, University of Wisconsin - Madison, Madison, Wisconsin, USA
| | - Arnaud Taton
- Division of Biological Sciences, University of California San Diego, La Jolla, California, USA
| | - Meng Li
- School of Oceanography, University of Washington, Seattle, Washington, USA
| | - Jodi N Young
- School of Oceanography, University of Washington, Seattle, Washington, USA
| | - Betül Kaçar
- Department of Bacteriology, University of Wisconsin - Madison, Madison, Wisconsin, USA
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2
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Mao Y, Catherall E, Díaz-Ramos A, Greiff GRL, Azinas S, Gunn L, McCormick AJ. The small subunit of Rubisco and its potential as an engineering target. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:543-561. [PMID: 35849331 PMCID: PMC9833052 DOI: 10.1093/jxb/erac309] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/07/2022] [Indexed: 05/06/2023]
Abstract
Rubisco catalyses the first rate-limiting step in CO2 fixation and is responsible for the vast majority of organic carbon present in the biosphere. The function and regulation of Rubisco remain an important research topic and a longstanding engineering target to enhance the efficiency of photosynthesis for agriculture and green biotechnology. The most abundant form of Rubisco (Form I) consists of eight large and eight small subunits, and is found in all plants, algae, cyanobacteria, and most phototrophic and chemolithoautotrophic proteobacteria. Although the active sites of Rubisco are located on the large subunits, expression of the small subunit regulates the size of the Rubisco pool in plants and can influence the overall catalytic efficiency of the Rubisco complex. The small subunit is now receiving increasing attention as a potential engineering target to improve the performance of Rubisco. Here we review our current understanding of the role of the small subunit and our growing capacity to explore its potential to modulate Rubisco catalysis using engineering biology approaches.
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Affiliation(s)
- Yuwei Mao
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
| | - Ella Catherall
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
| | - Aranzazú Díaz-Ramos
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
| | - George R L Greiff
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Stavros Azinas
- Department of Cell and Molecular Biology, Uppsala University, S-751 24 Uppsala, Sweden
| | - Laura Gunn
- Department of Cell and Molecular Biology, Uppsala University, S-751 24 Uppsala, Sweden
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, USA
| | - Alistair J McCormick
- SynthSys & Institute of Molecular Plant Sciences, School of Biological Sciences, King’s Buildings, University of Edinburgh, Edingburgh EH9 3BF, UK
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3
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Schulz L, Guo Z, Zarzycki J, Steinchen W, Schuller JM, Heimerl T, Prinz S, Mueller-Cajar O, Erb TJ, Hochberg GKA. Evolution of increased complexity and specificity at the dawn of form I Rubiscos. Science 2022; 378:155-160. [PMID: 36227987 DOI: 10.1126/science.abq1416] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The evolution of ribulose-1,5-bisphosphate carboxylase/oxygenases (Rubiscos) that discriminate strongly between their substrate carbon dioxide and the undesired side substrate dioxygen was an important event for photosynthetic organisms adapting to an oxygenated environment. We use ancestral sequence reconstruction to recapitulate this event. We show that Rubisco increased its specificity and carboxylation efficiency through the gain of an accessory subunit before atmospheric oxygen was present. Using structural and biochemical approaches, we retrace how this subunit was gained and became essential. Our work illuminates the emergence of an adaptation to rising ambient oxygen levels, provides a template for investigating the function of interactions that have remained elusive because of their essentiality, and sheds light on the determinants of specificity in Rubisco.
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Affiliation(s)
- Luca Schulz
- Department of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Zhijun Guo
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Jan Zarzycki
- Department of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Wieland Steinchen
- Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, 35043 Marburg, Germany.,Department of Chemistry, Philipps University Marburg, 35043 Marburg, Germany
| | - Jan M Schuller
- Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, 35043 Marburg, Germany.,Department of Chemistry, Philipps University Marburg, 35043 Marburg, Germany
| | - Thomas Heimerl
- Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, 35043 Marburg, Germany.,Department of Biology, Philipps University Marburg, 35043 Marburg, Germany
| | - Simone Prinz
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Oliver Mueller-Cajar
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Tobias J Erb
- Department of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany.,Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, 35043 Marburg, Germany
| | - Georg K A Hochberg
- Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, 35043 Marburg, Germany.,Department of Chemistry, Philipps University Marburg, 35043 Marburg, Germany.,Evolutionary Biochemistry Group, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
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4
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Schreiber M, Rensing SA, Gould SB. The greening ashore. TRENDS IN PLANT SCIENCE 2022; 27:847-857. [PMID: 35739050 DOI: 10.1016/j.tplants.2022.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 03/30/2022] [Accepted: 05/05/2022] [Indexed: 06/15/2023]
Abstract
More than half a billion years ago a streptophyte algal lineage began terraforming the terrestrial habitat and the Earth's atmosphere. This pioneering step enabled the subsequent evolution of all complex life on land, and the past decade has uncovered that many traits, both morphological and genetic, once thought to be unique to land plants, are conserved across some streptophyte algae. They provided the common ancestor of land plants with a repertoire of genes, of which many were adapted to overcome the new biotic and abiotic challenges. Exploring these molecular adaptations in non-tracheophyte species may help us to better prepare all green life, including our crops, for the challenges precipitated by the climate change of the Anthropocene because the challenges mostly differ by the speed with which they are now being met.
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Affiliation(s)
- Mona Schreiber
- Plant Cell Biology, University of Marburg, 35043 Marburg, Germany.
| | - Stefan A Rensing
- Plant Cell Biology, University of Marburg, 35043 Marburg, Germany; Centre for Biological Signalling Studies (BIOSS), University of Freiburg, Freiburg, Germany.
| | - Sven B Gould
- Institute for Molecular Evolution, Heinrich Heine University (HHU) Düsseldorf, 40225 Düsseldorf, Germany.
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5
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Kędzior M, Garcia AK, Li M, Taton A, Adam ZR, Young JN, Kaçar B. Resurrected Rubisco suggests uniform carbon isotope signatures over geologic time. Cell Rep 2022; 39:110726. [PMID: 35476992 DOI: 10.1016/j.celrep.2022.110726] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/26/2022] [Accepted: 03/30/2022] [Indexed: 11/30/2022] Open
Abstract
The earliest geochemical indicators of microbes-and the enzymes that powered them-extend back ∼3.8 Ga on Earth. Paleobiologists often attempt to understand these indicators by assuming that the behaviors of extant microbes and enzymes are uniform with those of their predecessors. This consistency in behavior seems at odds with our understanding of the inherent variability of living systems. Here, we examine whether a uniformitarian assumption for an enzyme thought to generate carbon isotope indicators of biological activity, RuBisCO, can be corroborated by independently studying the history of changes recorded within RuBisCO's genetic sequences. We resurrected a Precambrian-age RuBisCO by engineering its ancient DNA inside a cyanobacterium genome and measured the engineered organism's fitness and carbon-isotope-discrimination profile. Results indicate that Precambrian uniformitarian assumptions may be warranted but with important caveats. Experimental studies illuminating early innovations are crucial to explore the molecular foundations of life's earliest traces.
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Affiliation(s)
- Mateusz Kędzior
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA; NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Amanda K Garcia
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA; NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Meng Li
- School of Oceanography, University of Washington, Seattle, WA 98195, USA
| | - Arnaud Taton
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Zachary R Adam
- NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Geosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jodi N Young
- School of Oceanography, University of Washington, Seattle, WA 98195, USA
| | - Betül Kaçar
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA; NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI 53706, USA.
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6
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Lin MT, Salihovic H, Clark FK, Hanson MR. Improving the efficiency of Rubisco by resurrecting its ancestors in the family Solanaceae. SCIENCE ADVANCES 2022; 8:eabm6871. [PMID: 35427154 PMCID: PMC9012466 DOI: 10.1126/sciadv.abm6871] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Plants and photosynthetic organisms have a remarkably inefficient enzyme named Rubisco that fixes atmospheric CO2 into organic compounds. Understanding how Rubisco has evolved in response to past climate change is important for attempts to adjust plants to future conditions. In this study, we developed a computational workflow to assemble de novo both large and small subunits of Rubisco enzymes from transcriptomics data. Next, we predicted sequences for ancestral Rubiscos of the (nightshade) family Solanaceae and characterized their kinetics after coexpressing them in Escherichia coli. Predicted ancestors of C3 Rubiscos were identified that have superior kinetics and excellent potential to help plants adapt to anthropogenic climate change. Our findings also advance understanding of the evolution of Rubisco's catalytic traits.
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7
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Blake LI, Cann MJ. Carbon Dioxide and the Carbamate Post-Translational Modification. Front Mol Biosci 2022; 9:825706. [PMID: 35300111 PMCID: PMC8920986 DOI: 10.3389/fmolb.2022.825706] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/03/2022] [Indexed: 01/10/2023] Open
Abstract
Carbon dioxide is essential for life. It is at the beginning of every life process as a substrate of photosynthesis. It is at the end of every life process as the product of post-mortem decay. Therefore, it is not surprising that this gas regulates such diverse processes as cellular chemical reactions, transport, maintenance of the cellular environment, and behaviour. Carbon dioxide is a strategically important research target relevant to crop responses to environmental change, insect vector-borne disease and public health. However, we know little of carbon dioxide’s direct interactions with the cell. The carbamate post-translational modification, mediated by the nucleophilic attack by carbon dioxide on N-terminal α-amino groups or the lysine ɛ-amino groups, is one mechanism by which carbon dioxide might alter protein function to form part of a sensing and signalling mechanism. We detail known protein carbamates, including the history of their discovery. Further, we describe recent studies on new techniques to isolate this problematic post-translational modification.
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8
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Summons RE, Welander PV, Gold DA. Lipid biomarkers: molecular tools for illuminating the history of microbial life. Nat Rev Microbiol 2022; 20:174-185. [PMID: 34635851 DOI: 10.1038/s41579-021-00636-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2021] [Indexed: 11/09/2022]
Abstract
Fossilized lipids preserved in sedimentary rocks offer singular insights into the Earth's palaeobiology. These 'biomarkers' encode information pertaining to the oxygenation of the atmosphere and oceans, transitions in ocean plankton, the greening of continents, mass extinctions and climate change. Historically, biomarker interpretations relied on inventories of lipids present in extant microorganisms and counterparts in natural environments. However, progress has been impeded because only a small fraction of the Earth's microorganisms can be cultured, many environmentally significant microorganisms from the past no longer exist and there are gaping holes in knowledge concerning lipid biosynthesis. The revolution in genomics and bioinformatics has provided new tools to expand our understanding of lipid biomarkers, their biosynthetic pathways and distributions in nature. In this Review, we explore how preserved organic molecules provide a unique perspective on the history of the Earth's microbial life. We discuss how advances in molecular biology have helped elucidate biomarker origins and afforded more robust interpretations of fossil lipids and how the rock record provides vital calibration points for molecular clocks. Such studies are open to further exploitation with the expansion of sequenced microbial genomes in accessible databases.
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Affiliation(s)
- Roger E Summons
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - Paula V Welander
- Department of Earth System Science, Stanford University, Stanford, CA, USA
| | - David A Gold
- Department of Earth & Planetary Sciences, University of California Davis, Davis, CA, USA
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9
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An Insight of RuBisCO Evolution through a Multilevel Approach. Biomolecules 2021; 11:biom11121761. [PMID: 34944405 PMCID: PMC8698309 DOI: 10.3390/biom11121761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/15/2021] [Accepted: 10/23/2021] [Indexed: 12/28/2022] Open
Abstract
RuBisCO is the most abundant enzyme on earth; it regulates the organic carbon cycle in the biosphere. Studying its structural evolution will help to develop new strategies of genetic improvement in order to increase food production and mitigate CO2 emissions. In the present work, we evaluate how the evolution of sequence and structure among isoforms I, II and III of RuBisCO defines their intrinsic flexibility and residue-residue interactions. To do this, we used a multilevel approach based on phylogenetic inferences, multiple sequence alignment, normal mode analysis, and molecular dynamics. Our results show that the three isoforms exhibit greater fluctuation in the loop between αB and βC, and also present a positive correlation with loop 6, an important region for enzymatic activity because it regulates RuBisCO conformational states. Likewise, an increase in the flexibility of the loop structure between αB and βC, as well as Lys330 (form II) and Lys322 (form III) of loop 6, is important to increase photosynthetic efficiency. Thus, the cross-correlation dynamics analysis showed changes in the direction of movement of the secondary structures in the three isoforms. Finally, key amino acid residues related to the flexibility of the RuBisCO structure were indicated, providing important information for its enzymatic engineering.
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10
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Kędzior M, Kacar B. Quantification of RuBisCO Expression and Photosynthetic Oxygen Evolution in Cyanobacteria. Bio Protoc 2021; 11:e4199. [PMID: 34761071 PMCID: PMC8554809 DOI: 10.21769/bioprotoc.4199] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 08/02/2021] [Accepted: 08/06/2021] [Indexed: 11/02/2022] Open
Abstract
Phototrophic microorganisms are frequently engineered to regulate the expression and the activity of targeted enzymes of interest for specific biotechnological and agricultural applications. This protocol describes a method to evaluate the expression of RuBisCO (ribulose 1,5-bisphosphate carboxylase/oxygenase) in the model cyanobacterium Synechococcus elongatus PCC 7942, at both the transcript and protein levels by quantitative PCR and Western blot, respectively. We further describe an experimental method to determine photosynthetic activity using an oxygen electrode that measures the rate of molecular oxygen production by cyanobacterial cultures. Our protocol can be utilized to assess the effects of RuBisCO engineering at the metabolic and physiological levels.
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Affiliation(s)
- Mateusz Kędzior
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Betul Kacar
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
- Department of Bacteriology, University of Wisconsin-Madison, USA
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11
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Garcia AK, Cavanaugh CM, Kacar B. The curious consistency of carbon biosignatures over billions of years of Earth-life coevolution. THE ISME JOURNAL 2021; 15:2183-2194. [PMID: 33846565 PMCID: PMC8319343 DOI: 10.1038/s41396-021-00971-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 03/12/2021] [Accepted: 03/25/2021] [Indexed: 11/09/2022]
Abstract
The oldest and most wide-ranging signal of biological activity (biosignature) on our planet is the carbon isotope composition of organic materials preserved in rocks. These biosignatures preserve the long-term evolution of the microorganism-hosted metabolic machinery responsible for producing deviations in the isotopic compositions of inorganic and organic carbon. Despite billions of years of ecosystem turnover, evolutionary innovation, organismic complexification, and geological events, the organic carbon that is a residuum of the global marine biosphere in the rock record tells an essentially static story. The ~25‰ mean deviation between inorganic and organic 13C/12C values has remained remarkably unchanged over >3.5 billion years. The bulk of this record is conventionally attributed to early-evolved, RuBisCO-mediated CO2 fixation that, in extant oxygenic phototrophs, produces comparable isotopic effects and dominates modern primary production. However, billions of years of environmental transition, for example, in the progressive oxygenation of the Earth's atmosphere, would be expected to have accompanied shifts in the predominant RuBisCO forms as well as enzyme-level adaptive responses in RuBisCO CO2-specificity. These factors would also be expected to result in preserved isotopic signatures deviating from those produced by extant RuBisCO in oxygenic phototrophs. Why does the bulk carbon isotope record not reflect these expected environmental transitions and evolutionary innovations? Here, we discuss this apparent discrepancy and highlight the need for greater quantitative understanding of carbon isotope fractionation behavior in extant metabolic pathways. We propose novel, laboratory-based approaches to reconstructing ancestral states of carbon metabolisms and associated enzymes that can constrain isotopic biosignature production in ancient biological systems. Together, these strategies are crucial for integrating the complementary toolsets of biological and geological sciences and for interpretation of the oldest record of life on Earth.
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Affiliation(s)
- Amanda K Garcia
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Colleen M Cavanaugh
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Betul Kacar
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA.
- Lunar and Planetary Laboratory and Steward Observatory, University of Arizona, Tucson, AZ, USA.
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12
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Asplund-Samuelsson J, Hudson EP. Wide range of metabolic adaptations to the acquisition of the Calvin cycle revealed by comparison of microbial genomes. PLoS Comput Biol 2021; 17:e1008742. [PMID: 33556078 PMCID: PMC7895386 DOI: 10.1371/journal.pcbi.1008742] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 02/19/2021] [Accepted: 01/25/2021] [Indexed: 11/21/2022] Open
Abstract
Knowledge of the genetic basis for autotrophic metabolism is valuable since it relates to both the emergence of life and to the metabolic engineering challenge of incorporating CO2 as a potential substrate for biorefining. The most common CO2 fixation pathway is the Calvin cycle, which utilizes Rubisco and phosphoribulokinase enzymes. We searched thousands of microbial genomes and found that 6.0% contained the Calvin cycle. We then contrasted the genomes of Calvin cycle-positive, non-cyanobacterial microbes and their closest relatives by enrichment analysis, ancestral character estimation, and random forest machine learning, to explore genetic adaptations associated with acquisition of the Calvin cycle. The Calvin cycle overlaps with the pentose phosphate pathway and glycolysis, and we could confirm positive associations with fructose-1,6-bisphosphatase, aldolase, and transketolase, constituting a conserved operon, as well as ribulose-phosphate 3-epimerase, ribose-5-phosphate isomerase, and phosphoglycerate kinase. Additionally, carbohydrate storage enzymes, carboxysome proteins (that raise CO2 concentration around Rubisco), and Rubisco activases CbbQ and CbbX accompanied the Calvin cycle. Photorespiration did not appear to be adapted specifically for the Calvin cycle in the non-cyanobacterial microbes under study. Our results suggest that chemoautotrophy in Calvin cycle-positive organisms was commonly enabled by hydrogenase, and less commonly ammonia monooxygenase (nitrification). The enrichment of specific DNA-binding domains indicated Calvin-cycle associated genetic regulation. Metabolic regulatory adaptations were illustrated by negative correlation to AraC and the enzyme arabinose-5-phosphate isomerase, which suggests a downregulation of the metabolite arabinose-5-phosphate, which may interfere with the Calvin cycle through enzyme inhibition and substrate competition. Certain domains of unknown function that were found to be important in the analysis may indicate yet unknown regulatory mechanisms in Calvin cycle-utilizing microbes. Our gene ranking provides targets for experiments seeking to improve CO2 fixation, or engineer novel CO2-fixing organisms.
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Affiliation(s)
- Johannes Asplund-Samuelsson
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Solna, Sweden
| | - Elton P. Hudson
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Solna, Sweden
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13
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Ślesak I, Ślesak H. The activity of RubisCO and energy demands for its biosynthesis. Comparative studies with CO 2-reductases. JOURNAL OF PLANT PHYSIOLOGY 2021; 257:153337. [PMID: 33421837 DOI: 10.1016/j.jplph.2020.153337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 10/14/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
Most CO2 on Earth is fixed into organic matter via reactions catalysed by enzymes called carboxylases. CO2-fixation via carboxylases occurs in the Calvin-Benson-Bassham (CBB) cycle, and the crucial role in this cycle is played by RubisCO (D-ribulose 1,5-bisphosphate carboxylase/oxygenase). CO2 can also be fixed by pathways, where a reduction of CO2 to formate or carbon monoxide (CO) occurs. The latter reactions are performed by so-called CO2-reductases e.g. formate dehydrogenase (FDH), carbon-monooxide (CO) dehydrogenase (CODH), and crotonyl-CoA reductase/carboxylase (CCR). In general, a simple model of enzymatic activity based only on a turnover rate of an enzyme for an appropriate substrate (kcat) is insufficient. Based on estimated metabolic costs of each amino acid, the average energetic costs of amino acid biosynthesis (Eaa), and the total costs (ET) for selected CO2-fixing enzymes were analyzed concerning 1) kcat for CO2 (kC), and 2) specificity factor (Srel) for RubisCO. A comparison of Eaa and ET to their kC showed that CODH and FDHs do not need to be more efficient enzymes in CO2 capturing pathways than some forms of RubisCO. CCR was the only both low-cost and highly active CO2-fixing enzyme. The obtained results showed also that there exists an evolutionarily conserved trade-off between Srel of RubisCOs and the energetic demands needed for their biosynthesis. Phylogenetic analysis demonstrated that RubisCO, CODH, FDH, and CCR are enzymes formed as a result of parallel evolution. Moreover, the kinetic parameters (kC) of CO2-fixing enzymes were plausibly optimized already at the early stages of life evolution on Earth.
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Affiliation(s)
- Ireneusz Ślesak
- The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239, Kraków, Poland.
| | - Halina Ślesak
- Institute of Botany, Faculty of Biology, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
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14
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Hurley SJ, Wing BA, Jasper CE, Hill NC, Cameron JC. Carbon isotope evidence for the global physiology of Proterozoic cyanobacteria. SCIENCE ADVANCES 2021; 7:7/2/eabc8998. [PMID: 33893090 PMCID: PMC7787495 DOI: 10.1126/sciadv.abc8998] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 11/11/2020] [Indexed: 05/03/2023]
Abstract
Ancestral cyanobacteria are assumed to be prominent primary producers after the Great Oxidation Event [≈2.4 to 2.0 billion years (Ga) ago], but carbon isotope fractionation by extant marine cyanobacteria (α-cyanobacteria) is inconsistent with isotopic records of carbon fixation by primary producers in the mid-Proterozoic eon (1.8 to 1.0 Ga ago). To resolve this disagreement, we quantified carbon isotope fractionation by a wild-type planktic β-cyanobacterium (Synechococcus sp. PCC 7002), an engineered Proterozoic analog lacking a CO2-concentrating mechanism, and cyanobacterial mats. At mid-Proterozoic pH and pCO2 values, carbon isotope fractionation by the wild-type β-cyanobacterium is fully consistent with the Proterozoic carbon isotope record, suggesting that cyanobacteria with CO2-concentrating mechanisms were apparently the major primary producers in the pelagic Proterozoic ocean, despite atmospheric CO2 levels up to 100 times modern. The selectively permeable microcompartments central to cyanobacterial CO2-concentrating mechanisms ("carboxysomes") likely emerged to shield rubisco from O2 during the Great Oxidation Event.
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Affiliation(s)
- Sarah J Hurley
- Department of Geological Sciences, University of Colorado Boulder, Boulder, CO 80302, USA.
- Renewable and Sustainable Energy Institute, University of Colorado, Boulder, CO 80309, USA
| | - Boswell A Wing
- Department of Geological Sciences, University of Colorado Boulder, Boulder, CO 80302, USA
| | - Claire E Jasper
- Department of Geological Sciences, University of Colorado Boulder, Boulder, CO 80302, USA
| | - Nicholas C Hill
- Renewable and Sustainable Energy Institute, University of Colorado, Boulder, CO 80309, USA
- Department of Biochemistry, University of Colorado, Boulder, CO 80309, USA
| | - Jeffrey C Cameron
- Renewable and Sustainable Energy Institute, University of Colorado, Boulder, CO 80309, USA.
- Department of Biochemistry, University of Colorado, Boulder, CO 80309, USA
- National Renewable Energy Laboratory, Golden, CO 80401, USA
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15
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Biophysical analysis of the structural evolution of substrate specificity in RuBisCO. Proc Natl Acad Sci U S A 2020; 117:30451-30457. [PMID: 33199597 DOI: 10.1073/pnas.2018939117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is the most abundant enzyme on Earth. However, its catalytic rate per molecule of protein is extremely slow and the binding of the primary substrate, CO2, is competitively displaced by O2. Hence, carbon fixation by RuBisCO is highly inefficient; indeed, in higher C3 plants, about 30% of the time the enzyme mistakes CO2 for O2 Using genomic and structural analysis, we identify regions around the catalytic site that play key roles in discriminating between CO2 and O2 Our analysis identified positively charged cavities directly around the active site, which are expanded as the enzyme evolved with higher substrate specificity. The residues that extend these cavities have recently been under selective pressure, indicating that larger charged pockets are a feature of modern RuBisCOs, enabling greater specificity for CO2 This paper identifies a key structural feature that enabled the enzyme to evolve improved CO2 sequestration in an oxygen-rich atmosphere and may guide the engineering of more efficient RuBisCOs.
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16
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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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17
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Garcia AK, McShea H, Kolaczkowski B, Kaçar B. Reconstructing the evolutionary history of nitrogenases: Evidence for ancestral molybdenum-cofactor utilization. GEOBIOLOGY 2020; 18:394-411. [PMID: 32065506 PMCID: PMC7216921 DOI: 10.1111/gbi.12381] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 12/23/2019] [Accepted: 01/22/2020] [Indexed: 05/08/2023]
Abstract
The nitrogenase metalloenzyme family, essential for supplying fixed nitrogen to the biosphere, is one of life's key biogeochemical innovations. The three forms of nitrogenase differ in their metal dependence, each binding either a FeMo-, FeV-, or FeFe-cofactor where the reduction of dinitrogen takes place. The history of nitrogenase metal dependence has been of particular interest due to the possible implication that ancient marine metal availabilities have significantly constrained nitrogenase evolution over geologic time. Here, we reconstructed the evolutionary history of nitrogenases, and combined phylogenetic reconstruction, ancestral sequence inference, and structural homology modeling to evaluate the potential metal dependence of ancient nitrogenases. We find that active-site sequence features can reliably distinguish extant Mo-nitrogenases from V- and Fe-nitrogenases and that inferred ancestral sequences at the deepest nodes of the phylogeny suggest these ancient proteins most resemble modern Mo-nitrogenases. Taxa representing early-branching nitrogenase lineages lack one or more biosynthetic nifE and nifN genes that both contribute to the assembly of the FeMo-cofactor in studied organisms, suggesting that early Mo-nitrogenases may have utilized an alternate and/or simplified pathway for cofactor biosynthesis. Our results underscore the profound impacts that protein-level innovations likely had on shaping global biogeochemical cycles throughout the Precambrian, in contrast to organism-level innovations that characterize the Phanerozoic Eon.
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Affiliation(s)
- Amanda K. Garcia
- Department of Molecular and Cellular BiologyUniversity of ArizonaTucsonArizona
| | - Hanon McShea
- Department of Earth System ScienceStanford UniversityStanfordCalifornia
| | - Bryan Kolaczkowski
- Department of Microbiology and Cell ScienceUniversity of FloridaGainesvilleFlorida
| | - Betül Kaçar
- Department of Molecular and Cellular BiologyUniversity of ArizonaTucsonArizona
- Steward Observatory and the Lunar and Planetary LaboratoryUniversity of ArizonaTucsonArizona
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18
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Iñiguez C, Capó-Bauçà S, Niinemets Ü, Stoll H, Aguiló-Nicolau P, Galmés J. Evolutionary trends in RuBisCO kinetics and their co-evolution with CO 2 concentrating mechanisms. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:897-918. [PMID: 31820505 DOI: 10.1111/tpj.14643] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 11/15/2019] [Accepted: 11/27/2019] [Indexed: 05/19/2023]
Abstract
RuBisCO-catalyzed CO2 fixation is the main source of organic carbon in the biosphere. This enzyme is present in all domains of life in different forms (III, II, and I) and its origin goes back to 3500 Mya, when the atmosphere was anoxygenic. However, the RuBisCO active site also catalyzes oxygenation of ribulose 1,5-bisphosphate, therefore, the development of oxygenic photosynthesis and the subsequent oxygen-rich atmosphere promoted the appearance of CO2 concentrating mechanisms (CCMs) and/or the evolution of a more CO2 -specific RuBisCO enzyme. The wide variability in RuBisCO kinetic traits of extant organisms reveals a history of adaptation to the prevailing CO2 /O2 concentrations and the thermal environment throughout evolution. Notable differences in the kinetic parameters are found among the different forms of RuBisCO, but the differences are also associated with the presence and type of CCMs within each form, indicative of co-evolution of RuBisCO and CCMs. Trade-offs between RuBisCO kinetic traits vary among the RuBisCO forms and also among phylogenetic groups within the same form. These results suggest that different biochemical and structural constraints have operated on each type of RuBisCO during evolution, probably reflecting different environmental selective pressures. In a similar way, variations in carbon isotopic fractionation of the enzyme point to significant differences in its relationship to the CO2 specificity among different RuBisCO forms. A deeper knowledge of the natural variability of RuBisCO catalytic traits and the chemical mechanism of RuBisCO carboxylation and oxygenation reactions raises the possibility of finding unrevealed landscapes in RuBisCO evolution.
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Affiliation(s)
- Concepción Iñiguez
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, Palma, Balearic Islands, Spain
| | - Sebastià Capó-Bauçà
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, Palma, Balearic Islands, Spain
| | - Ülo Niinemets
- Chair of Crop Science and Plant Biology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, 51006, Tartu, Estonia
- Estonian Academy of Sciences, Kohtu 6, 10130, Tallinn, Estonia
| | - Heather Stoll
- Department of Earth Sciences, ETH Zürich, Sonnegstrasse 5, 8092, Zürich, Switzerland
| | - Pere Aguiló-Nicolau
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, Palma, Balearic Islands, Spain
| | - Jeroni Galmés
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, Palma, Balearic Islands, Spain
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19
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Garcia AK, Kaçar B. How to resurrect ancestral proteins as proxies for ancient biogeochemistry. Free Radic Biol Med 2019; 140:260-269. [PMID: 30951835 DOI: 10.1016/j.freeradbiomed.2019.03.033] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 02/11/2019] [Accepted: 03/26/2019] [Indexed: 10/27/2022]
Abstract
Throughout the history of life, enzymes have served as the primary molecular mediators of biogeochemical cycles by catalyzing the metabolic pathways that interact with geochemical substrates. The byproducts of enzymatic activities have been preserved as chemical and isotopic signatures in the geologic record. However, interpretations of these signatures are limited by the assumption that such enzymes have remained functionally conserved over billions of years of molecular evolution. By reconstructing ancient genetic sequences in conjunction with laboratory enzyme resurrection, preserved biogeochemical signatures can instead be related to experimentally constrained, ancestral enzymatic properties. We may thereby investigate instances within molecular evolutionary trajectories potentially tied to significant biogeochemical transitions evidenced in the geologic record. Here, we survey recent enzyme resurrection studies to provide a reasoned assessment of areas of success and common pitfalls relevant to ancient biogeochemical applications. We conclude by considering the Great Oxidation Event, which provides a constructive example of a significant biogeochemical transition that warrants investigation with ancestral enzyme resurrection. This event also serves to highlight the pitfalls of facile interpretation of paleophenotype models and data, as applied to two examples of enzymes that likely both influenced and were influenced by the rise of atmospheric oxygen - RuBisCO and nitrogenase.
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Affiliation(s)
- Amanda K Garcia
- Department of Molecular and Cell Biology, University of Arizona, Tucson, AZ, 85721, USA
| | - Betül Kaçar
- Department of Molecular and Cell Biology, University of Arizona, Tucson, AZ, 85721, USA; Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ, 85721, USA.
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20
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Braakman R. Evolution of cellular metabolism and the rise of a globally productive biosphere. Free Radic Biol Med 2019; 140:172-187. [PMID: 31082508 DOI: 10.1016/j.freeradbiomed.2019.05.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 02/28/2019] [Accepted: 05/02/2019] [Indexed: 01/14/2023]
Abstract
Metabolic processes in cells and chemical processes in the environment are fundamentally intertwined and have evolved in concert for most of Earth's existence. Here I argue that intrinsic properties of cellular metabolism imposed central constraints on the historical trajectories of biopsheric productivity and atmospheric oxygenation. Photosynthesis depends on iron, but iron is highly insoluble under the aerobic conditions produced by oxygenic photosynthesis. These counteracting constraints led to two major stages of Earth oxygenation. After a cyanobacteria-driven biospheric expansion near the Archean-Proterozoic boundary, productivity remained largely restricted to continental boundaries and shallow aquatic environments where weathering inputs made iron more accessible. The anoxic deep open ocean was rich in free iron during the Proterozoic, but this iron was largely inaccessible, partly because an otherwise nutrient-poor ocean was limiting to photosynthesis, but also because a photosynthetic expansion would have quenched its own iron supply. Near the Proterozoic-Phanerozoic boundary, bioenergetics innovations allowed eukaryotic photosynthesis to overcome these interconnected negative feedbacks and begin expanding into the deep open oceans and onto the continents, where nutrients are inherently harder to come by. Key insights into what drove the ecological rise of eukaryotic photosynthesis emerge from analyses of marine Synechococcus and Prochlorococcus, abundant marine picocyanobacteria whose ancestors colonized the oceans in the Neoproterozoic. The reconstructed evolution of this group reveals a sequence of innovations that ultimately produced a form of photosynthesis in Prochlorococcus that is more like that of green plant cells than other cyanobacteria. Innovations increased the energy flux of cells, thereby enhancing their ability to acquire sparse nutrients, and as by-product also increased the production of organic carbon waste. Some of these organic waste products had the ability to chelate iron and make it bioavailable, thereby indirectly pushing the oceans through a transition from an anoxic state rich in free iron to an oxygenated state with organic carbon-bound iron. Resulting conditions (and parallel processes on the continents) in turn led to a series of positive feedbacks that increased the availability of other nutrients, thereby promoting the rise of a globally productive biosphere. In addition to the occurrence of major biospheric expansions, the several hundred million-year periods around the Archean-Proterozoic and Proterozoic-Phanerozoic boundaries share a number of other parallels. Both epochs have also been linked to major carbon cycle perturbations and global glaciations, as well as changes in the nature of plate tectonics and increases in continental exposure and weathering. This suggests the dynamics of life and Earth are intimately intertwined across many levels and that general principles governed transitions in these coupled dynamics at both times in Earth history.
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Affiliation(s)
- Rogier Braakman
- Department of Civil & Environmental Engineering, Massachusetts Institute of Technology, USA; Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, USA.
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21
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Rickaby REM, Eason Hubbard MR. Upper ocean oxygenation, evolution of RuBisCO and the Phanerozoic succession of phytoplankton. Free Radic Biol Med 2019; 140:295-304. [PMID: 31075497 PMCID: PMC6856715 DOI: 10.1016/j.freeradbiomed.2019.05.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 04/10/2019] [Accepted: 05/02/2019] [Indexed: 12/13/2022]
Abstract
Evidence is compiled to demonstrate a redox scale within Earth's photosynthesisers that correlates the specificity of their RuBisCO with organismal metabolic tolerance to anoxia, and ecological selection by dissolved O2/CO2 and nutrients. The Form 1B RuBisCO found in the chlorophyte green algae, has a poor selectivity between the two dissolved substrates, O2 and CO2, at the active site. This enzyme appears adapted to lower O2/CO2 ratios, or more "anoxic" conditions and therefore requires additional energetic or nutrient investment in a carbon concentrating mechanism (CCM) to boost the intracellular CO2/O2 ratio and maintain competitive carboxylation rates under increasingly high O2/CO2 conditions in the environment. By contrast the coccolithophores and diatoms evolved containing the more selective Rhodophyte Form 1D RuBisCO, better adapted to a higher O2/CO2 ratio, or more oxic conditions. This Form 1D RuBisCO requires lesser energetic or nutrient investment in a CCM to attain high carboxylation rates under environmentally high O2/CO2 ratios. Such a physiological relationship may underpin the succession of phytoplankton in the Phanerozoic oceans: the coccolithophores and diatoms took over the oceanic realm from the incumbent cyanobacteria and green algae when the upper ocean became persistently oxygenated, alkaline and more oligotrophic. The facultatively anaerobic green algae, able to tolerate the anoxic conditions of the water column and a periodically inundated soil, were better poised to adapt to the fluctuating anoxia associated with periods of submergence and emergence and transition onto the land. The induction of a CCM may exert a natural limit to the improvement of RuBisCO efficiency over Earth history. Rubisco specificity appears to adapt on the timescale of ∼100 Myrs. So persistent elevation of CO2/O2 ratios in the intracellular environment around the enzyme, may induce a relaxation in RuBisCO selectivity for CO2 relative to O2. The most efficient RuBisCO for net carboxylation is likely to be found in CCM-lacking algae that have been exposed to hyperoxic conditions for at least 100 Myrs, such as intertidal brown seaweeds.
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Affiliation(s)
- Rosalind E M Rickaby
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK.
| | - M R Eason Hubbard
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK
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22
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23
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Walker SI, Bains W, Cronin L, DasSarma S, Danielache S, Domagal-Goldman S, Kacar B, Kiang NY, Lenardic A, Reinhard CT, Moore W, Schwieterman EW, Shkolnik EL, Smith HB. Exoplanet Biosignatures: Future Directions. ASTROBIOLOGY 2018; 18:779-824. [PMID: 29938538 PMCID: PMC6016573 DOI: 10.1089/ast.2017.1738] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 03/13/2018] [Indexed: 05/08/2023]
Abstract
We introduce a Bayesian method for guiding future directions for detection of life on exoplanets. We describe empirical and theoretical work necessary to place constraints on the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate and geophysics, geochemical cycling, the universalities of physics and chemistry, the contingencies of evolutionary history, the properties of life as an emergent complex system, and the mechanisms driving the emergence of life. We provide examples for how the Bayesian formalism could guide future search strategies, including determining observations to prioritize or deciding between targeted searches or larger lower resolution surveys to generate ensemble statistics and address how a Bayesian methodology could constrain the prior probability of life with or without a positive detection. Key Words: Exoplanets-Biosignatures-Life detection-Bayesian analysis. Astrobiology 18, 779-824.
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Affiliation(s)
- Sara I. Walker
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona
- Blue Marble Space Institute of Science, Seattle, Washington
| | - William Bains
- EAPS (Earth, Atmospheric and Planetary Science), MIT, Cambridge, Massachusetts
- Rufus Scientific Ltd., Royston, United Kingdom
| | - Leroy Cronin
- School of Chemistry, University of Glasgow, Glasgow, United Kingdom
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, Institute of Marine and Environmental Technology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Sebastian Danielache
- Department of Materials and Life Science, Faculty of Science and Technology, Sophia University, Tokyo, Japan
- Earth Life Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - Shawn Domagal-Goldman
- NASA Goddard Space Flight Center, Greenbelt, Maryland
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
| | - Betul Kacar
- Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts
- NASA Astrobiology Institute, Reliving the Past Team, University of Montana, Missoula, Montana
- Department of Molecular and Cell Biology, University of Arizona, Tucson, Arizona
- Department of Astronomy and Steward Observatory, University of Arizona, Tucson, Arizona
| | - Nancy Y. Kiang
- NASA Goddard Institute for Space Studies, New York, New York
| | - Adrian Lenardic
- Department of Earth Science, Rice University, Houston, Texas
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
| | - William Moore
- Department of Atmospheric and Planetary Sciences, Hampton University, Hampton, Virginia
- National Institute of Aerospace, Hampton, Virginia
| | - Edward W. Schwieterman
- Blue Marble Space Institute of Science, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
| | - Evgenya L. Shkolnik
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
| | - Harrison B. Smith
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
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25
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Kacar B, Guy L, Smith E, Baross J. Resurrecting ancestral genes in bacteria to interpret ancient biosignatures. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2017; 375:20160352. [PMID: 29133450 PMCID: PMC5686408 DOI: 10.1098/rsta.2016.0352] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/17/2017] [Indexed: 05/04/2023]
Abstract
Two datasets, the geologic record and the genetic content of extant organisms, provide complementary insights into the history of how key molecular components have shaped or driven global environmental and macroevolutionary trends. Changes in global physico-chemical modes over time are thought to be a consistent feature of this relationship between Earth and life, as life is thought to have been optimizing protein functions for the entirety of its approximately 3.8 billion years of history on the Earth. Organismal survival depends on how well critical genetic and metabolic components can adapt to their environments, reflecting an ability to optimize efficiently to changing conditions. The geologic record provides an array of biologically independent indicators of macroscale atmospheric and oceanic composition, but provides little in the way of the exact behaviour of the molecular components that influenced the compositions of these reservoirs. By reconstructing sequences of proteins that might have been present in ancient organisms, we can downselect to a subset of possible sequences that may have been optimized to these ancient environmental conditions. How can one use modern life to reconstruct ancestral behaviours? Configurations of ancient sequences can be inferred from the diversity of extant sequences, and then resurrected in the laboratory to ascertain their biochemical attributes. One way to augment sequence-based, single-gene methods to obtain a richer and more reliable picture of the deep past, is to resurrect inferred ancestral protein sequences in living organisms, where their phenotypes can be exposed in a complex molecular-systems context, and then to link consequences of those phenotypes to biosignatures that were preserved in the independent historical repository of the geological record. As a first step beyond single-molecule reconstruction to the study of functional molecular systems, we present here the ancestral sequence reconstruction of the beta-carbonic anhydrase protein. We assess how carbonic anhydrase proteins meet our selection criteria for reconstructing ancient biosignatures in the laboratory, which we term palaeophenotype reconstruction.This article is part of the themed issue 'Reconceptualizing the origins of life'.
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Affiliation(s)
- Betul Kacar
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Lionel Guy
- Department of Medical Biochemistry and Microbiology, Uppsala University, 75123 Uppsala, Sweden
| | - Eric Smith
- Earth-Science Life Institute, Meguro-ku, Tokyo 152-8550, Japan
- Santa Fe Institute, Santa Fe, NM 87501, USA
| | - John Baross
- The School of Oceanography, University of Washington, Seattle, WA 98105, USA
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