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Shoemaker A, Maritan A, Cosar S, Nupp S, Menchaca A, Jackson T, Dang A, Baxter BK, Colman DR, Dunham EC, Boyd ES. Wood-Ljungdahl pathway encoding anaerobes facilitate low-cost primary production in hypersaline sediments at Great Salt Lake, Utah. FEMS Microbiol Ecol 2024; 100:fiae105. [PMID: 39054286 PMCID: PMC11287216 DOI: 10.1093/femsec/fiae105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Revised: 07/03/2024] [Accepted: 07/24/2024] [Indexed: 07/27/2024] Open
Abstract
Little is known of primary production in dark hypersaline ecosystems despite the prevalence of such environments on Earth today and throughout its geologic history. Here, we generated and analyzed metagenome-assembled genomes (MAGs) organized as operational taxonomic units (OTUs) from three depth intervals along a 30-cm sediment core from the north arm of Great Salt Lake, Utah. The sediments and associated porewaters were saturated with NaCl, exhibited redox gradients with depth, and harbored nitrogen-depleted organic carbon. Metabolic predictions of MAGs representing 36 total OTUs recovered from the core indicated that communities transitioned from aerobic and heterotrophic at the surface to anaerobic and autotrophic at depth. Dark CO2 fixation was detected in sediments and the primary mode of autotrophy was predicted to be via the Wood-Ljungdahl pathway. This included novel hydrogenotrophic acetogens affiliated with the bacterial class Candidatus Bipolaricaulia. Minor populations were dependent on the Calvin cycle and the reverse tricarboxylic acid cycle, including in a novel Thermoplasmatota MAG. These results are interpreted to reflect the favorability of and selectability for populations that operate the lowest energy requiring CO2-fixation pathway known, the Wood-Ljungdahl pathway, in anoxic and hypersaline conditions that together impart a higher energy demand on cells.
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Affiliation(s)
- Anna Shoemaker
- Department of Earth Sciences, Montana State University, P.O. Box 173480, Bozeman, MT 59717, United States
| | - Andrew Maritan
- Department of Microbiology and Cell Biology, Montana State University, P.O. Box 173520, Bozeman, MT 59717, United States
| | - Su Cosar
- Department of Microbiology and Cell Biology, Montana State University, P.O. Box 173520, Bozeman, MT 59717, United States
| | - Sylvia Nupp
- Department of Chemistry and Biochemistry, Montana State University, P.O. Box 173400, Bozeman, MT 59717, United States
| | - Ana Menchaca
- Department of Microbiology and Cell Biology, Montana State University, P.O. Box 173520, Bozeman, MT 59717, United States
| | - Thomas Jackson
- Department of Microbiology and Cell Biology, Montana State University, P.O. Box 173520, Bozeman, MT 59717, United States
| | - Aria Dang
- Department of Chemistry and Biochemistry, Montana State University, P.O. Box 173400, Bozeman, MT 59717, United States
| | - Bonnie K Baxter
- Great Salt Lake Institute, Westminster University, 1840 South 1300 East, Salt Lake City, UT 84105, United States
| | - Daniel R Colman
- Department of Microbiology and Cell Biology, Montana State University, P.O. Box 173520, Bozeman, MT 59717, United States
| | - Eric C Dunham
- Department of Microbiology and Cell Biology, Montana State University, P.O. Box 173520, Bozeman, MT 59717, United States
| | - Eric S Boyd
- Department of Microbiology and Cell Biology, Montana State University, P.O. Box 173520, Bozeman, MT 59717, United States
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2
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Scharf C, Witkowski O. Rebuilding the Habitable Zone from the Bottom up with Computational Zones. ASTROBIOLOGY 2024; 24:613-627. [PMID: 38853680 DOI: 10.1089/ast.2023.0035] [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: 06/11/2024]
Abstract
Computation, if treated as a set of physical processes that act on information represented by states of matter, encompasses biological systems, digital systems, and other constructs and may be a fundamental measure of living systems. The opportunity for biological computation, represented in the propagation and selection-driven evolution of information-carrying organic molecular structures, has been partially characterized in terms of planetary habitable zones (HZs) based on primary conditions such as temperature and the presence of liquid water. A generalization of this concept to computational zones (CZs) is proposed, with constraints set by three principal characteristics: capacity (including computation rates), energy, and instantiation (or substrate, including spatial extent). CZs naturally combine traditional habitability factors, including those associated with biological function that incorporate the chemical milieu, constraints on nutrients and free energy, as well as element availability. Two example applications are presented by examining the fundamental thermodynamic work efficiency and Landauer limit of photon-driven biological computation on planetary surfaces and of generalized computation in stellar energy capture structures (a.k.a. Dyson structures). It is suggested that CZs that involve nested structures or substellar objects could manifest unique observational signatures as cool far-infrared emitters. While these latter scenarios are entirely hypothetical, they offer a useful, complementary introduction to the potential universality of CZs.
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Affiliation(s)
- Caleb Scharf
- NASA Ames Research Center, Moffett Field, California, USA
| | - Olaf Witkowski
- Cross Labs, Cross Compass Ltd., Kyoto, Japan
- College of Arts and Sciences, University of Tokyo, Tokyo, Japan
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3
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Cockell CS, Hallsworth JE, McMahon S, Kane SR, Higgins PM. The Concept of Life on Venus Informs the Concept of Habitability. ASTROBIOLOGY 2024; 24:628-634. [PMID: 38800952 DOI: 10.1089/ast.2023.0106] [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: 05/29/2024]
Abstract
An enduring question in astrobiology is how we assess extraterrestrial environments as being suitable for life. We suggest that the most reliable assessments of the habitability of extraterrestrial environments are made with respect to the empirically determined limits to known life. We discuss qualitatively distinct categories of habitability: empirical habitability that is constrained by the observed limits to biological activity; habitability sensu stricto, which is defined with reference to the known or unknown limits to the activity of all known organisms; and habitability sensu lato (habitability in the broadest sense), which is circumscribed by the limit of all possible life in the universe, which is the most difficult (and perhaps impossible) to determine. We use the cloud deck of Venus, which is temperate but incompatible with known life, as an example to elaborate and hypothesize on these limits.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - John E Hallsworth
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, United Kingdom
| | - Sean McMahon
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Stephen R Kane
- Department of Earth and Planetary Sciences, University of California, Riverside, California, USA
| | - Peter M Higgins
- Department of Earth Sciences, University of Toronto, Toronto, Canada
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4
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Bains W, Petkowski JJ, Seager S. Venus' Atmospheric Chemistry and Cloud Characteristics Are Compatible with Venusian Life. ASTROBIOLOGY 2024; 24:371-385. [PMID: 37306952 DOI: 10.1089/ast.2022.0113] [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: 06/13/2023]
Abstract
Venus is Earth's sister planet, with similar mass and density but an uninhabitably hot surface, an atmosphere with a water activity 50-100 times lower than anywhere on Earths' surface, and clouds believed to be made of concentrated sulfuric acid. These features have been taken to imply that the chances of finding life on Venus are vanishingly small, with several authors describing Venus' clouds as "uninhabitable," and that apparent signs of life there must therefore be abiotic, or artefactual. In this article, we argue that although many features of Venus can rule out the possibility that Earth life could live there, none rule out the possibility of all life based on what we know of the physical principle of life on Earth. Specifically, there is abundant energy, the energy requirements for retaining water and capturing hydrogen atoms to build biomass are not excessive, defenses against sulfuric acid are conceivable and have terrestrial precedent, and the speculative possibility that life uses concentrated sulfuric acid as a solvent instead of water remains. Metals are likely to be available in limited supply, and the radiation environment is benign. The clouds can support a biomass that could readily be detectable by future astrobiology-focused space missions from its impact on the atmosphere. Although we consider the prospects for finding life on Venus to be speculative, they are not absent. The scientific reward from finding life in such an un-Earthlike environment justifies considering how observations and missions should be designed to be capable of detecting life if it is there.
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Affiliation(s)
- William Bains
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom
| | - Janusz J Petkowski
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- JJ Scientific, Warsaw, Poland
| | - Sara Seager
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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5
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Ortega-Arzola E, Higgins PM, Cockell CS. The minimum energy required to build a cell. Sci Rep 2024; 14:5267. [PMID: 38438463 PMCID: PMC11306549 DOI: 10.1038/s41598-024-54303-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 02/11/2024] [Indexed: 03/06/2024] Open
Abstract
Understanding the energy requirements for cell synthesis accurately and comprehensively has been a longstanding challenge. We introduce a computational model that estimates the minimum energy necessary to build any cell from its constituent parts. This method combines omics and internal cell compositions from various sources to calculate the Gibbs Free Energy of biosynthesis independently of specific metabolic pathways. Our public tool, Synercell, can be used with other models for minumum species-specific energy estimations in any well-sequenced species. The energy for synthesising the genome, transcriptome, proteome, and lipid bilayer of four cell types: Escherichia coli, Saccharomyces cerevisiae, an average mammalian cell and JCVI-syn3A were estimated. Their modelled minimum synthesis energies at 298 K were 9.54 × 10 - 11 J/cell, 4.99 × 10 - 9 J/cell, 3.71 × 10 - 7 J/cell and 3.69 × 10 - 12 respectively. Gram-for-gram synthesis of lipid bilayers requires the most energy, followed by the proteome, genome, and transcriptome. The average per gram cost of biomass synthesis is in the 300s of J/g for all four cells. Implications for the generalisability of cell construction and applications to biogeosciences, cellular biology, biotechnology, and astrobiology are discussed.
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Affiliation(s)
- Edwin Ortega-Arzola
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK.
| | - Peter M Higgins
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
- Department of Earth Sciences, University of Toronto, Toronto, ON, Canada
| | - Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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6
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Thweatt JL, Harman CE, Araújo MN, Marlow JJ, Oliver GC, Sabuda MC, Sevgen S, Wilpiszeki RL. Chapter 6: The Breadth and Limits of Life on Earth. ASTROBIOLOGY 2024; 24:S124-S142. [PMID: 38498824 DOI: 10.1089/ast.2021.0131] [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: 03/20/2024]
Abstract
Scientific ideas about the potential existence of life elsewhere in the universe are predominantly informed by knowledge about life on Earth. Over the past ∼4 billion years, life on Earth has evolved into millions of unique species. Life now inhabits nearly every environmental niche on Earth that has been explored. Despite the wide variety of species and diverse biochemistry of modern life, many features, such as energy production mechanisms and nutrient requirements, are conserved across the Tree of Life. Such conserved features help define the operational parameters required by life and therefore help direct the exploration and evaluation of habitability in extraterrestrial environments. As new diversity in the Tree of Life continues to expand, so do the known limits of life on Earth and the range of environments considered habitable elsewhere. The metabolic processes used by organisms living on the edge of habitability provide insights into the types of environments that would be most suitable to hosting extraterrestrial life, crucial for planning and developing future astrobiology missions. This chapter will introduce readers to the breadth and limits of life on Earth and show how the study of life at the extremes can inform the broader field of astrobiology.
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Affiliation(s)
- Jennifer L Thweatt
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, Pennsylvania, USA. (Former)
| | - C E Harman
- Planetary Systems Branch, NASA Ames Research Center, Moffett Field, California, USA
| | - M N Araújo
- Biochemistry Department, University of São Paulo, São Carlos, Brazil
| | - Jeffrey J Marlow
- Department of Biology, Boston University, Boston, Massachusetts, USA
| | - Gina C Oliver
- Department of Geology, San Bernardino Valley College, San Bernardino, California, USA
| | - Mary C Sabuda
- Department of Earth and Environmental Sciences, University of Minnesota-Twin Cities, Minneapolis, Minnesota, USA
- Biotechnology Institute, University of Minnesota-Twin Cities, St. Paul, Minnesota, USA
| | - Serhat Sevgen
- Institute of Marine Sciences, Middle East Technical University, Erdemli, Mersin, Turkey
- Blue Marble Space Institute of Science, Seattle, Washington, USA
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7
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Qin X, Ren X, Wang X, Liu J, Wu H, Zeng X, Sun Y, Chen Z, Zhang S, Zhang Y, Chen W, Liu B, Liu D, Guo L, Li K, Zeng X, Huang H, Zhang Q, Yu S, Li C, Guo Z. Modern water at low latitudes on Mars: Potential evidence from dune surfaces. SCIENCE ADVANCES 2023; 9:eadd8868. [PMID: 37115933 PMCID: PMC10146874 DOI: 10.1126/sciadv.add8868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Landforms on the Martian surface are critical to understanding the nature of surface processes in the recent past. However, modern hydroclimatic conditions on Mars remain enigmatic, as explanations for the formation of observed landforms are ambiguous. We report crusts, cracks, aggregates, and bright polygonal ridges on the surfaces of hydrated salt-rich dunes of southern Utopia Planitia (~25°N) from in situ exploration by the Zhurong rover. These surface features were inferred to form after 1.4 to 0.4 million years ago. Wind and CO2 frost processes can be ruled out as potential mechanisms. Instead, involvement of saline water from thawed frost/snow is the most likely cause. This discovery sheds light on more humid conditions of the modern Martian climate and provides critical clues to future exploration missions searching for signs of extant life, particularly at low latitudes with comparatively warmer, more amenable surface temperatures.
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Affiliation(s)
- Xiaoguang Qin
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
- Corresponding author. (X.Q.); (X.R.); (X.W.); (J.L.)
| | - Xin Ren
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
- Corresponding author. (X.Q.); (X.R.); (X.W.); (J.L.)
| | - Xu Wang
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
- Corresponding author. (X.Q.); (X.R.); (X.W.); (J.L.)
| | - Jianjun Liu
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
- Corresponding author. (X.Q.); (X.R.); (X.W.); (J.L.)
| | - Haibin Wu
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
- College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xingguo Zeng
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Yong Sun
- Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
| | - Zhaopeng Chen
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Shihao Zhang
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
| | - Yizhong Zhang
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Wangli Chen
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Bin Liu
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Dawei Liu
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Lin Guo
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Kangkang Li
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
| | - Xiangzhao Zeng
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Hai Huang
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Qing Zhang
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Songzheng Yu
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Chunlai Li
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
| | - Zhengtang Guo
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
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8
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Yang Y, Pan H, Li X, Luo W, Bharti B. Applications of two-dimensional ion chromatography for analytes determination in environmental matrix: A review. J Chromatogr A 2023; 1694:463908. [PMID: 36913814 DOI: 10.1016/j.chroma.2023.463908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 02/22/2023] [Accepted: 03/01/2023] [Indexed: 03/06/2023]
Abstract
Ion chromatography (IC) has grown in usage rapidly since its first introduction in 1975. However, IC is still sometimes unable to separate target analytes from coexisting components well with identical elution time, due to the limited resolution and column capacity, especially in the presence of high-level salt matrix. These limitations hence drive IC to develop two-dimensional IC (2D-IC). In this review, we capture the 2D-IC applications in environmental samples via the perspective of coupling different IC columns, which aim to summarize where these 2D-IC methods fit in. In sequence, we firstly review the principles of 2D-IC and emphasize one-pump column-switching IC (OPCS IC) because it is a simplified 2D-IC that only uses one set of IC system. We then compare typical 2D-IC and OPCS IC performances in terms of application scope, method detection limit, drawbacks, and expectations. Finally, we propose some challenges of current methods and opportunities for future research. For instance, it is challenging to couple anion exchange column and capillary column in OPCS IC due to the incompatibility between flow path dimensions and suppressor; coupling ion exclusion column and mixed-bed column may be promising to simultaneously determine anions and cations in weak acids or salts. The details of this study may help practitioners to better understand and implement 2D-IC methods and meanwhile motivate researchers to fill in the knowledge gap in the future.
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Affiliation(s)
- Yang Yang
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, Harbin Institute of Technology (Shenzhen), 518055, PR. China.
| | - Huimei Pan
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, Harbin Institute of Technology (Shenzhen), 518055, PR. China
| | - Xiao Li
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, Harbin Institute of Technology (Shenzhen), 518055, PR. China
| | - Wang Luo
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, Harbin Institute of Technology (Shenzhen), 518055, PR. China
| | - Bandna Bharti
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, Harbin Institute of Technology (Shenzhen), 518055, PR. China; Department of Chemistry, DAV University, Jalandhar, Punjab 144001, India
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9
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Nixon SL, Bonsall E, Cockell CS. Limitations of microbial iron reduction under extreme conditions. FEMS Microbiol Rev 2022; 46:6645348. [PMID: 35849069 PMCID: PMC9629499 DOI: 10.1093/femsre/fuac033] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 06/23/2022] [Accepted: 07/15/2022] [Indexed: 01/09/2023] Open
Abstract
Microbial iron reduction is a widespread and ancient metabolism on Earth, and may plausibly support microbial life on Mars and beyond. Yet, the extreme limits of this metabolism are yet to be defined. To investigate this, we surveyed the recorded limits to microbial iron reduction in a wide range of characterized iron-reducing microorganisms (n = 141), with a focus on pH and temperature. We then calculated Gibbs free energy of common microbially mediated iron reduction reactions across the pH-temperature habitability space to identify thermodynamic limits. Comparing predicted and observed limits, we show that microbial iron reduction is generally reported at extremes of pH or temperature alone, but not when these extremes are combined (with the exception of a small number of acidophilic hyperthermophiles). These patterns leave thermodynamically favourable combinations of pH and temperature apparently unoccupied. The empty spaces could be explained by experimental bias, but they could also be explained by energetic and biochemical limits to iron reduction at combined extremes. Our data allow for a review of our current understanding of the limits to microbial iron reduction at extremes and provide a basis to test more general hypotheses about the extent to which biochemistry establishes the limits to life.
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Affiliation(s)
- Sophie L Nixon
- Corresponding author: Department of Earth and Environmental Sciences, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK. E-mail:
| | - Emily Bonsall
- Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA, United Kingdom
| | - Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
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10
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MacKenzie SM, Neveu M, Davila AF, Lunine JI, Cable ML, Phillips-Lander CM, Eigenbrode JL, Waite JH, Craft KL, Hofgartner JD, McKay CP, Glein CR, Burton D, Kounaves SP, Mathies RA, Vance SD, Malaska MJ, Gold R, German CR, Soderlund KM, Willis P, Freissinet C, McEwen AS, Brucato JR, de Vera JPP, Hoehler TM, Heldmann J. Science Objectives for Flagship-Class Mission Concepts for the Search for Evidence of Life at Enceladus. ASTROBIOLOGY 2022; 22:685-712. [PMID: 35290745 PMCID: PMC9233532 DOI: 10.1089/ast.2020.2425] [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] [Indexed: 05/07/2023]
Abstract
Cassini revealed that Saturn's Moon Enceladus hosts a subsurface ocean that meets the accepted criteria for habitability with bio-essential elements and compounds, liquid water, and energy sources available in the environment. Whether these conditions are sufficiently abundant and collocated to support life remains unknown and cannot be determined from Cassini data. However, thanks to the plume of oceanic material emanating from Enceladus' south pole, a new mission to Enceladus could search for evidence of life without having to descend through kilometers of ice. In this article, we outline the science motivations for such a successor to Cassini, choosing the primary science goal to be determining whether Enceladus is inhabited and assuming a resource level equivalent to NASA's Flagship-class missions. We selected a set of potential biosignature measurements that are complementary and orthogonal to build a robust case for any life detection result. This result would be further informed by quantifications of the habitability of the environment through geochemical and geophysical investigations into the ocean and ice shell crust. This study demonstrates that Enceladus' plume offers an unparalleled opportunity for in situ exploration of an Ocean World and that the planetary science and astrobiology community is well equipped to take full advantage of it in the coming decades.
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Affiliation(s)
- Shannon M. MacKenzie
- Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
- Address correspondence to: Shannon M. MacKenzie, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA
| | - Marc Neveu
- Department of Astronomy, University of Maryland, College Park, Maryland, USA
- Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - Alfonso F. Davila
- Division of Space Science and Astrobiology, NASA Ames Research Center, Moffett Field, California, USA
| | - Jonathan I. Lunine
- Department of Astronomy, Cornell University, Ithaca, New York, USA
- Carl Sagan Institute, Cornell University, Ithaca, New York, USA
| | - Morgan L. Cable
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | | | - Jennifer L. Eigenbrode
- Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - J. Hunter Waite
- Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA
| | - Kate L. Craft
- Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
| | - Jason D. Hofgartner
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Chris P. McKay
- Division of Space Science and Astrobiology, NASA Ames Research Center, Moffett Field, California, USA
| | - Christopher R. Glein
- Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA
| | - Dana Burton
- Department of Anthropology, George Washington University, Washington, District of Columbia, USA
| | | | - Richard A. Mathies
- Chemistry Department and Space Sciences Laboratory, University of California, Berkeley, Berkeley, California, USA
| | - Steven D. Vance
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Michael J. Malaska
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Robert Gold
- Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
| | - Christopher R. German
- Department of Geology & Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
| | - Krista M. Soderlund
- Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA
| | - Peter Willis
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | | | - Alfred S. McEwen
- Lunar and Planetary Lab, University of Arizona, Tucson, Arizona, USA
| | | | - Jean-Pierre P. de Vera
- Space Operations and Astronaut Training, MUSC, German Aerospace Center (DLR), Cologne, Germany
| | - Tori M. Hoehler
- Division of Space Science and Astrobiology, NASA Ames Research Center, Moffett Field, California, USA
| | - Jennifer Heldmann
- Division of Space Science and Astrobiology, NASA Ames Research Center, Moffett Field, California, USA
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11
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Cockell CS, Samuels T, Stevens AH. Habitability Is Binary, But It Is Used by Astrobiologists to Encompass Continuous Ecological Questions. ASTROBIOLOGY 2022; 22:7-13. [PMID: 34756098 DOI: 10.1089/ast.2021.0038] [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: 06/13/2023]
Abstract
The term "habitability" is pervasive throughout the space sciences and astrobiology literature and is broadly used to describe an environment's ability to support life. Here, we argue that, while it is fundamentally a binary matter whether an organism can persist in an environment or not, these binary assessments lead to continuous ecological measurements that are often collected under the umbrella term "habitability" by astrobiologists. Although the use of habitability in this way has provided a framework for those studying the potential of environments to support life, including comparative analyses between terrestrial and extraterrestrial environments, it can also generate confusion and limit interdisciplinary understanding. Namely, differing ecological metrics used as proxies for habitability can yield differing conclusions depending upon the metrics chosen. Therefore, we suggest that in this continuous sense, the terms habitable and habitability lose meaning unless the specific scientific question and biological metric chosen to address it are defined. As a corollary, the search for universal single metrics to make habitability assessments is not to be encouraged, and as we argue, attempting to do so would oversimply analyses of the ability of environments to support life.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Toby Samuels
- Geomicrobiology Group, Centre for Applied Geoscience, University of Tübingen, Tübingen, Germany
| | - Adam H Stevens
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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12
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Méndez A, Rivera-Valentín EG, Schulze-Makuch D, Filiberto J, Ramírez RM, Wood TE, Dávila A, McKay C, Ceballos KNO, Jusino-Maldonado M, Torres-Santiago NJ, Nery G, Heller R, Byrne PK, Malaska MJ, Nathan E, Simões MF, Antunes A, Martínez-Frías J, Carone L, Izenberg NR, Atri D, Chitty HIC, Nowajewski-Barra P, Rivera-Hernández F, Brown CY, Lynch KL, Catling D, Zuluaga JI, Salazar JF, Chen H, González G, Jagadeesh MK, Haqq-Misra J. Habitability Models for Astrobiology. ASTROBIOLOGY 2021; 21:1017-1027. [PMID: 34382857 DOI: 10.1089/ast.2020.2342] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Habitability has been generally defined as the capability of an environment to support life. Ecologists have been using Habitat Suitability Models (HSMs) for more than four decades to study the habitability of Earth from local to global scales. Astrobiologists have been proposing different habitability models for some time, with little integration and consistency among them, being different in function to those used by ecologists. Habitability models are not only used to determine whether environments are habitable, but they also are used to characterize what key factors are responsible for the gradual transition from low to high habitability states. Here we review and compare some of the different models used by ecologists and astrobiologists and suggest how they could be integrated into new habitability standards. Such standards will help improve the comparison and characterization of potentially habitable environments, prioritize target selections, and study correlations between habitability and biosignatures. Habitability models are the foundation of planetary habitability science, and the synergy between ecologists and astrobiologists is necessary to expand our understanding of the habitability of Earth, the Solar System, and extrasolar planets.
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Affiliation(s)
- Abel Méndez
- Planetary Habitability Laboratory, University of Puerto Rico at Arecibo, Puerto Rico, USA
| | | | - Dirk Schulze-Makuch
- Center for Astronomy and Astrophysics, Technische Universität Berlin, Berlin, Germany; German Research Centre for Geosciences, Section Geomicrobiology, Potsdam, Germany; Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany
| | | | - Ramses M Ramírez
- University of Central Florida, Department of Physics, Orlando, Florida, USA; Space Science Institute, Boulder, Colorado, USA
| | - Tana E Wood
- USDA Forest Service International Institute of Tropical Forestry, San Juan, Puerto Rico, USA
| | - Alfonso Dávila
- NASA Ames Research Center, Moffett Field, California, USA
| | - Chris McKay
- NASA Ames Research Center, Moffett Field, California, USA
| | - Kevin N Ortiz Ceballos
- Planetary Habitability Laboratory, University of Puerto Rico at Arecibo, Puerto Rico, USA
| | | | | | | | - René Heller
- Max Planck Institute for Solar System Research; Institute for Astrophysics, University of Göttingen, Germany
| | - Paul K Byrne
- North Carolina State University, Raleigh, North Carolina, USA
| | - Michael J Malaska
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Erica Nathan
- Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, USA
| | - Marta Filipa Simões
- State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau SAR, China
| | - André Antunes
- State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau SAR, China
| | | | | | - Noam R Izenberg
- Johns Hopkins Applied Physics Laboratory, Laurel, Maryland, USA
| | - Dimitra Atri
- Center for Space Science, New York University Abu Dhabi, United Arab Emirates
| | | | | | | | | | - Kennda L Lynch
- Lunar and Planetary Institute, USRA, Houston, Texas, USA
| | | | - Jorge I Zuluaga
- Institute of Physics / FCEN - Universidad de Antioquia, Medellín, Colombia
| | - Juan F Salazar
- GIGA, Escuela Ambiental, Facultad de Ingeniería, Universidad de Antioquia, Medellín, Colombia
| | - Howard Chen
- Northwestern University, Evanston, Illinois, USA
| | - Grizelle González
- USDA Forest Service International Institute of Tropical Forestry, San Juan, Puerto Rico, USA
| | | | - Jacob Haqq-Misra
- Blue Marble Space Institute of Science, Seattle, Washington, USA
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13
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Abstract
Astrobiology is focused on the study of life in the universe. However, lifeless planetary environments yield biological information on the variety of ways in which physical and chemical conditions in the universe preclude the possibility of the origin or persistence of life, and in turn this will help explain the distribution and abundance of life, or lack of it, in the universe. Furthermore, many places that humans wish to explore and settle in space are lifeless, and studying the fate of life in these environments will aid our own success in thriving in them. In this synthetic review, I have three objectives, as follows: (1) To discuss the biological value and use of lifeless environments, (2) To explore the diverse planetary bodies and environments that can be lifeless and to categorize them, and (3) To propose sets of biological experiments that can be undertaken in different categories of lifeless worlds and environments and suggest concepts for mission ideas to realize these goals. They include origin of life and microbial inoculation experiments in lifeless but habitable environments. I suggest that the biological study of lifelessness is an underappreciated area in planetary sciences.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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14
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Cockell CS, Wordsworth R, Whiteford N, Higgins PM. Minimum Units of Habitability and Their Abundance in the Universe. ASTROBIOLOGY 2021; 21:481-489. [PMID: 33513037 DOI: 10.1089/ast.2020.2350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Although the search for habitability is a much-vaunted objective in the study of planetary environments, the material requirements for an environment to be habitable can be met with relatively few ingredients. In this hypothesis paper, the minimum material requirements for habitability are first re-evaluated, necessarily based on life "as we know it." From this vantage point, we explore examples of the minimum number of material requirements for habitable conditions to arise in a planetary environment, which we illustrate with "minimum habitability diagrams." These requirements raise the hypothesis that habitable conditions may be common throughout the universe. If the hypothesis was accepted, then the discovery of life would remain an important discovery, but habitable conditions on their own would be an unremarkable feature of the material universe. We discuss how minimum units of habitability provide a parsimonious way to consider the minimum number of geological inferences about a planetary body, and the minimum number of atmospheric components that must be measured, for example in the case of exoplanets, to be able to make assessments of habitability.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Robin Wordsworth
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
| | - Niall Whiteford
- Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh, UK
| | - Peter M Higgins
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
- Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh, UK
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15
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Cockell CS, McMahon S, Biddle JF. When is Life a Viable Hypothesis? The Case of Venusian Phosphine. ASTROBIOLOGY 2021; 21:261-264. [PMID: 33337946 DOI: 10.1089/ast.2020.2390] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Affiliation(s)
- Charles S Cockell
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - Sean McMahon
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
- School of Geosciences, University of Edinburgh, Edinburgh, UK
| | - Jennifer F Biddle
- School of Marine Science and Policy, University of Delaware, Newark, Delaware, USA
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16
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Schulze-Makuch D, Heller R, Guinan E. In Search for a Planet Better than Earth: Top Contenders for a Superhabitable World. ASTROBIOLOGY 2020; 20:1394-1404. [PMID: 32955925 PMCID: PMC7757576 DOI: 10.1089/ast.2019.2161] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 08/07/2020] [Indexed: 06/11/2023]
Abstract
The fact that Earth is teeming with life makes it appear odd to ask whether there could be other planets in our galaxy that may be even more suitable for life. Neglecting this possible class of "superhabitable" planets, however, could be considered anthropocentric and geocentric biases. Most important from the perspective of an observer searching for extrasolar life is that such a search might be executed most effectively with a focus on superhabitable planets instead of Earth-like planets. We argue that there could be regions of astrophysical parameter space of star-planet systems that could allow for planets to be even better for life than our Earth. We aim to identify those parameters and their optimal ranges, some of which are astrophysically motivated, whereas others are based on the varying habitability of the natural history of our planet. Some of these conditions are far from being observationally testable on planets outside the solar system. Still, we can distill a short list of 24 top contenders among the >4000 exoplanets known today that could be candidates for a superhabitable planet. In fact, we argue that, with regard to the search for extrasolar life, potentially superhabitable planets may deserve higher priority for follow-up observations than most Earth-like planets.
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Affiliation(s)
- Dirk Schulze-Makuch
- Astrobiology Group, Center for Astronomy and Astrophysics, Technische Universität Berlin, Berlin, Germany
- GFZ German Research Center for Geosciences, Section Geomicrobiology, Potsdam, Germany
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department of Experimental Limnology, Stechlin, Germany
- School of the Environment, Washington State University, Pullman, Washington, USA
| | - René Heller
- Max Planck Institute for Solar System Research, Göttingen, Germany
- Institute for Astrophysics, Georg-August University, Göttingen, Germany
| | - Edward Guinan
- Department of Astrophysics and Planetary Science, Villanova University, Villanova, Pennsylvania, USA
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17
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Azua-Bustos A, Fairén AG, Silva CG, Carrizo D, Fernández-Martínez MÁ, Arenas-Fajardo C, Fernández-Sampedro M, Gil-Lozano C, Sánchez-García L, Ascaso C, Wierzchos J, Rampe EB. Inhabited subsurface wet smectites in the hyperarid core of the Atacama Desert as an analog for the search for life on Mars. Sci Rep 2020; 10:19183. [PMID: 33154541 PMCID: PMC7645800 DOI: 10.1038/s41598-020-76302-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 10/16/2020] [Indexed: 01/21/2023] Open
Abstract
The modern Martian surface is unlikely to be habitable due to its extreme aridity among other environmental factors. This is the reason why the hyperarid core of the Atacama Desert has been studied as an analog for the habitability of Mars for more than 50 years. Here we report a layer enriched in smectites located just 30 cm below the surface of the hyperarid core of the Atacama. We discovered the clay-rich layer to be wet (a phenomenon never observed before in this region), keeping a high and constant relative humidity of 78% (aw 0.780), and completely isolated from the changing and extremely dry subaerial conditions characteristic of the Atacama. The smectite-rich layer is inhabited by at least 30 halophilic species of metabolically active bacteria and archaea, unveiling a previously unreported habitat for microbial life under the surface of the driest place on Earth. The discovery of a diverse microbial community in smectite-rich subsurface layers in the hyperarid core of the Atacama, and the collection of biosignatures we have identified within the clays, suggest that similar shallow clay deposits on Mars may contain biosignatures easily reachable by current rovers and landers.
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Affiliation(s)
- Armando Azua-Bustos
- Centro de Astrobiología (CSIC-INTA), 28850, Madrid, Spain.
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile.
| | - Alberto G Fairén
- Centro de Astrobiología (CSIC-INTA), 28850, Madrid, Spain.
- Department of Astronomy, Cornell University, Ithaca, NY, 14853, USA.
| | | | - Daniel Carrizo
- Centro de Astrobiología (CSIC-INTA), 28850, Madrid, Spain
| | | | | | | | - Carolina Gil-Lozano
- Centro de Astrobiología (CSIC-INTA), 28850, Madrid, Spain
- Laboratory of Planetology and Geodynamics, Université de Nantes, 44322, Nantes, France
| | | | - Carmen Ascaso
- Museo Nacional de Ciencias Naturales (CSIC), 28006, Madrid, Spain
| | - Jacek Wierzchos
- Museo Nacional de Ciencias Naturales (CSIC), 28006, Madrid, Spain
| | - Elizabeth B Rampe
- Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX, USA
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18
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Higgins PM, Cockell CS. A bioenergetic model to predict habitability, biomass and biosignatures in astrobiology and extreme conditions. J R Soc Interface 2020; 17:20200588. [PMID: 33081642 PMCID: PMC7653372 DOI: 10.1098/rsif.2020.0588] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 09/24/2020] [Indexed: 12/23/2022] Open
Abstract
In order to grow, reproduce and evolve life requires a supply of energy and nutrients. Astrobiology has the challenge of studying life on Earth in environments which are poorly characterized or extreme, usually both, and predicting the habitability of extraterrestrial environments. We have developed a general astrobiological model for assessing the energetic and nutrient availability of poorly characterized environments to predict their potential biological productivity. NutMEG (nutrients, maintenance, energy and growth) can be used to estimate how much biomass an environment could host, and how that life might affect the local chemistry. It requires only an overall catabolic reaction and some knowledge of the local environment to begin making estimations, with many more customizable parameters, such as microbial adaptation. In this study, the model was configured to replicate laboratory data on the growth of methanogens. It was used to predict the effect of temperature and energy/nutrient limitation on their microbial growth rates, total biomass levels, and total biosignature production in laboratory-like conditions to explore how it could be applied to astrobiological problems. As temperature rises from 280 to 330 K, NutMEG predicts exponential drops in final biomass ([Formula: see text]) and total methane production ([Formula: see text]) despite an increase in peak growth rates ([Formula: see text]) for a typical methanogen in ideal conditions. This is caused by the increasing cost of microbial maintenance diverting energy away from growth processes. Restricting energy and nutrients exacerbates this trend. With minimal assumptions NutMEG can reliably replicate microbial growth behaviour, but better understanding of the synthesis and maintenance costs life must overcome in different extremes is required to improve its results further. NutMEG can help us assess the theoretical habitability of extraterrestrial environments and predict potential biomass and biosignature production, for example on exoplanets using minimum input parameters to guide observations.
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Affiliation(s)
- P. M. Higgins
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
| | - C. S. Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
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19
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Cockell CS. Persistence of Habitable, but Uninhabited, Aqueous Solutions and the Application to Extraterrestrial Environments. ASTROBIOLOGY 2020; 20:617-627. [PMID: 32105517 DOI: 10.1089/ast.2019.2179] [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] [Indexed: 06/10/2023]
Abstract
In most environments on Earth, habitable environments contain life. Experiments were conducted to investigate the decoupling of the presence of habitable conditions and life. A set of microcosms habitable for known groups of organisms, but uninhabited (i.e., uninhabited habitats), was exposed to external environmental conditions to test the hypothesis that extreme habitable environments can remain uninhabited for sustained time periods. These microcosms were made of tubes containing liquid water and inorganic N, P, and S. Organics (used as electron donors and as a C source) were provided as L and D amino acids. One set of uninhabited habitats contained no additional salts, one set contained saturated NaCl, and one set contained saturated MgSO4. A ddH2O control and a complex medium for Halobacterium were used as controls. The presence of organisms was tested by enumeration of colonists and sequencing of extracted DNA. At each time point, inoculation into fresh medium was used to test for growth of organisms. After 1 week, the "no salt" and saturated MgSO4 solutions were colonized. After 6 months, both the NaCl-saturated and Halobacterium solutions remained uninhabited, but all other samples were colonized. These experiments demonstrate that certain types of habitable liquid water environments exposed to microbial atmospheric inoculation, even on Earth, can remain devoid of reproducing life for many months. On other planetary bodies, such as Mars, these data imply the possibility of preserved transient water bodies that would record habitable conditions, but no evidence of life, even if life existed elsewhere on the planet.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, James Clerk Maxwell Building, The King's Buildings, University of Edinburgh, Edinburgh, United Kingdom
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20
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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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21
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Poulet F, Gross C, Horgan B, Loizeau D, Bishop JL, Carter J, Orgel C. Mawrth Vallis, Mars: A Fascinating Place for Future In Situ Exploration. ASTROBIOLOGY 2020; 20:199-234. [PMID: 31916851 DOI: 10.1089/ast.2019.2074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
After the successful landing of the Mars Science Laboratory rover, both NASA and ESA initiated a selection process for potential landing sites for the Mars2020 and ExoMars missions, respectively. Two ellipses located in the Mawrth Vallis region were proposed and evaluated during a series of meetings (three for Mars2020 mission and five for ExoMars). We describe here the regional context of the two proposed ellipses as well as the framework of the objectives of these two missions. Key science targets of the ellipses and their astrobiological interests are reported. This work confirms that the proposed ellipses contain multiple past martian wet environments of a subaerial, subsurface, and/or subaqueous character, in which to probe the past climate of Mars; build a broad picture of possible past habitable environments; evaluate their exobiological potentials; and search for biosignatures in well-preserved rocks. A mission scenario covering several key investigations during the nominal mission of each rover is also presented, as well as descriptions of how the site fulfills the science requirements and expectations of in situ martian exploration. These serve as a basis for potential future exploration of the Mawrth Vallis region with new missions and describe opportunities for human exploration of Mars in terms of resources and science discoveries.
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Affiliation(s)
- François Poulet
- Institut d'Astrophysique Spatiale, CNRS/Université Paris-Sud, Orsay, France
| | - Christoph Gross
- Institute of Geological Sciences, Planetary Sciences and Remote Sensing Group, Freie Universität Berlin, Berlin, Germany
| | | | - Damien Loizeau
- Institut d'Astrophysique Spatiale, CNRS/Université Paris-Sud, Orsay, France
| | | | - John Carter
- Institut d'Astrophysique Spatiale, CNRS/Université Paris-Sud, Orsay, France
| | - Csilla Orgel
- Institute of Geological Sciences, Planetary Sciences and Remote Sensing Group, Freie Universität Berlin, Berlin, Germany
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22
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Jones RM, Goordial JM, Orcutt BN. Corrigendum: Low Energy Subsurface Environments as Extraterrestrial Analogs. Front Microbiol 2019; 10:1959. [PMID: 31501654 PMCID: PMC6719285 DOI: 10.3389/fmicb.2019.01959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 08/08/2019] [Indexed: 11/25/2022] Open
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23
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Morono Y, Wishart JR, Ito M, Ijiri A, Hoshino T, Torres M, Verba C, Terada T, Inagaki F, Colwell FS. Microbial Metabolism and Community Dynamics in Hydraulic Fracturing Fluids Recovered From Deep Hydrocarbon-Rich Shale. Front Microbiol 2019; 10:376. [PMID: 30915042 PMCID: PMC6422894 DOI: 10.3389/fmicb.2019.00376] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 02/13/2019] [Indexed: 11/29/2022] Open
Abstract
Hydraulic fracturing is a prominent method of natural gas production that uses injected, high-pressure fluids to fracture low permeability, hydrocarbon rich strata such as shale. Upon completion of a well, the fluid returns to the surface (produced water) and contains natural gas, subsurface constituents, and microorganisms (Barbot et al., 2013; Daly et al., 2016). While the microbial community of the produced fluids has been studied in multiple gas wells, the activity of these microorganisms and their relation to biogeochemical activity is not well understood. In this experiment, we supplemented produced fluid with 13C-labeled carbon sources (glucose, acetate, bicarbonate, methanol, or methane), and 15N-labeled ammonium chloride in order to isotopically trace microbial activity over multiple day in anoxic incubations. Nanoscale secondary ion mass spectrometry (NanoSIMS) was used to generate isotopic images of 13C and 15N incorporation in individual cells, while isotope ratio monitoring–gas chromatography–mass spectrometry (IRM–GC–MS) was used to measure 13CO2, and 13CH4 as metabolic byproducts. Glucose, acetate, and methanol were all assimilated by microorganisms under anoxic conditions. 13CO2 production was only observed with glucose as a substrate indicating that catabolic activity was limited to this condition. The microbial communities observed at 0, 19, and 32 days of incubation did not vary between different carbon sources, were low in diversity, and composed primarily of the class Clostridia. The primary genera detected in the incubations, Halanaerobium and Fusibacter, are known to be adapted to harsh physical and chemical conditions consistent with those that occur in the hydrofracturing environment. This study provides evidence that microorganisms in produced fluid are revivable in laboratory incubations and retained the ability to metabolize added carbon and nitrogen substrates.
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Affiliation(s)
- Yuki Morono
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan.,Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Jessie R Wishart
- National Energy Technology Laboratory, United States Department of Energy, Albany, OR, United States
| | - Motoo Ito
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan.,Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Akira Ijiri
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan.,Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Tatsuhiko Hoshino
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan.,Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Marta Torres
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, United States
| | - Circe Verba
- National Energy Technology Laboratory, United States Department of Energy, Albany, OR, United States
| | | | - Fumio Inagaki
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan.,Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.,Research and Development Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
| | - Frederick S Colwell
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, United States
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24
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Methanogens: pushing the boundaries of biology. Emerg Top Life Sci 2018; 2:629-646. [PMID: 33525834 PMCID: PMC7289024 DOI: 10.1042/etls20180031] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 10/23/2018] [Accepted: 10/24/2018] [Indexed: 01/15/2023]
Abstract
Methanogens are anaerobic archaea that grow by producing methane gas. These microbes and their exotic metabolism have inspired decades of microbial physiology research that continues to push the boundary of what we know about how microbes conserve energy to grow. The study of methanogens has helped to elucidate the thermodynamic and bioenergetics basis of life, contributed our understanding of evolution and biodiversity, and has garnered an appreciation for the societal utility of studying trophic interactions between environmental microbes, as methanogens are important in microbial conversion of biogenic carbon into methane, a high-energy fuel. This review discusses the theoretical basis for energy conservation by methanogens and identifies gaps in methanogen biology that may be filled by undiscovered or yet-to-be engineered organisms.
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Wakai S. Biochemical and thermodynamic analyses of energy conversion in extremophiles. Biosci Biotechnol Biochem 2018; 83:49-64. [PMID: 30381012 DOI: 10.1080/09168451.2018.1538769] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
A variety of extreme environments, characterized by extreme values of various physicochemical parameters (temperature, pressure, salinity, pH, and so on), are found on Earth. Organisms that favorably live in such extreme environments are called extremophiles. All living organisms, including extremophiles, must acquire energy to maintain cellular homeostasis, including extremophiles. For energy conversion in harsh environments, thermodynamically useful reactions and stable biomolecules are essential. In this review, I briefly summarize recent studies of extreme environments and extremophiles living in these environments and describe energy conversion processes in various extremophiles based on my previous research. Furthermore, I discuss the correlation between the biological system of electrotrophy, a third biological energy acquisition system, and the mechanism underlying microbiologically influenced corrosion. These insights into energy conversion in extremophiles may improve our understanding of the "limits of life". Abbreviations: PPi: pyrophosphate; PPase: pyrophosphatase; ITC: isothermal titration microcalorimetry; SVNTase: Shewanella violacea 5'-nucleotidase; SANTase: Shewanella amazonensis 5'-nucleotidase.
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Affiliation(s)
- Satoshi Wakai
- a Graduate School of Science, Technology and Innovation , Kobe University , Kobe , Japan
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26
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Jones RM, Goordial JM, Orcutt BN. Low Energy Subsurface Environments as Extraterrestrial Analogs. Front Microbiol 2018; 9:1605. [PMID: 30072971 PMCID: PMC6058055 DOI: 10.3389/fmicb.2018.01605] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 06/27/2018] [Indexed: 11/13/2022] Open
Abstract
Earth's subsurface is often isolated from phototrophic energy sources and characterized by chemotrophic modes of life. These environments are often oligotrophic and limited in electron donors or electron acceptors, and include continental crust, subseafloor oceanic crust, and marine sediment as well as subglacial lakes and the subsurface of polar desert soils. These low energy subsurface environments are therefore uniquely positioned for examining minimum energetic requirements and adaptations for chemotrophic life. Current targets for astrobiology investigations of extant life are planetary bodies with largely inhospitable surfaces, such as Mars, Europa, and Enceladus. Subsurface environments on Earth thus serve as analogs to explore possibilities of subsurface life on extraterrestrial bodies. The purpose of this review is to provide an overview of subsurface environments as potential analogs, and the features of microbial communities existing in these low energy environments, with particular emphasis on how they inform the study of energetic limits required for life. The thermodynamic energetic calculations presented here suggest that free energy yields of reactions and energy density of some metabolic redox reactions on Mars, Europa, Enceladus, and Titan could be comparable to analog environments in Earth's low energy subsurface habitats.
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Affiliation(s)
| | | | - Beth N. Orcutt
- Bigelow Laboratory for Ocean Sciences, East Boothbay, ME, United States
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27
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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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28
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Altair T, de Avellar MGB, Rodrigues F, Galante D. Microbial habitability of Europa sustained by radioactive sources. Sci Rep 2018; 8:260. [PMID: 29321597 PMCID: PMC5762670 DOI: 10.1038/s41598-017-18470-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 12/12/2017] [Indexed: 11/09/2022] Open
Abstract
There is an increasing interest in the icy moons of the Solar System due to their potential habitability and as targets for future exploratory missions, which include astrobiological goals. Several studies have reported new results describing the details of these moons' geological settings; however, there is still a lack of information regarding the deep subsurface environment of the moons. The purpose of this article is to evaluate the microbial habitability of Europa constrained by terrestrial analogue environments and sustained by radioactive energy provided by natural unstable isotopes. The geological scenarios are based on known deep environments on Earth, and the bacterial ecosystem is based on a sulfate-reducing bacterial ecosystem found 2.8 km below the surface in a basin in South Africa. The results show the possibility of maintaining the modeled ecosystem based on the proposed scenarios and provides directions for future models and exploration missions for a more complete evaluation of the habitability of Europa and of icy moons in general.
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Affiliation(s)
- Thiago Altair
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM)., Av. Giuseppe Máximo Scolfaro, 10000, 13083-100, Campinas, SP, Brazil.,Programa de Pós-Graduação em Física Biomolecular, Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
| | - Marcio G B de Avellar
- Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo., Rua do Matão, 1226, 05508-090, São Paulo, SP, Brazil.
| | - Fabio Rodrigues
- Departamento de Química Fundamental Instituto de Química, Universidade de São Paulo., Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo, SP, Brazil
| | - Douglas Galante
- Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM)., Av. Giuseppe Máximo Scolfaro, 10000, 13083-100, Campinas, SP, Brazil.,Programa de Pós-Graduação em Física Biomolecular, Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
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29
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Garcia-Lopez E, Cid C. Glaciers and Ice Sheets As Analog Environments of Potentially Habitable Icy Worlds. Front Microbiol 2017; 8:1407. [PMID: 28804477 PMCID: PMC5532398 DOI: 10.3389/fmicb.2017.01407] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 07/11/2017] [Indexed: 01/09/2023] Open
Abstract
Icy worlds in the solar system and beyond have attracted a remarkable attention as possible habitats for life. The current consideration about whether life exists beyond Earth is based on our knowledge of life in terrestrial cold environments. On Earth, glaciers and ice sheets have been considered uninhabited for a long time as they seemed too hostile to harbor life. However, these environments are unique biomes dominated by microbial communities which maintain active biochemical routes. Thanks to techniques such as microscopy and more recently DNA sequencing methods, a great biodiversity of prokaryote and eukaryote microorganisms have been discovered. These microorganisms are adapted to a harsh environment, in which the most extreme features are the lack of liquid water, extremely cold temperatures, high solar radiation and nutrient shortage. Here we compare the environmental characteristics of icy worlds, and the environmental characteristics of terrestrial glaciers and ice sheets in order to address some interesting questions: (i) which are the characteristics of habitability known for the frozen worlds, and which could be compatible with life, (ii) what are the environmental characteristics of terrestrial glaciers and ice sheets that can be life-limiting, (iii) What are the microbial communities of prokaryotic and eukaryotic microorganisms that can live in them, and (iv) taking into account these observations, could any of these planets or satellites meet the conditions of habitability? In this review, the icy worlds are considered from the point of view of astrobiological exploration. With the aim of determining whether icy worlds could be potentially habitable, they have been compared with the environmental features of glaciers and ice sheets on Earth. We also reviewed some field and laboratory investigations about microorganisms that live in analog environments of icy worlds, where they are not only viable but also metabolically active.
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Affiliation(s)
| | - Cristina Cid
- Microbial Evolution Laboratory, Centro de Astrobiología (Consejo Superior de Investigaciones Cientificas-Instituto Nacional de Técnica Aeroespacial)Madrid, Spain
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30
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Hays LE, Graham HV, Des Marais DJ, Hausrath EM, Horgan B, McCollom TM, Parenteau MN, Potter-McIntyre SL, Williams AJ, Lynch KL. Biosignature Preservation and Detection in Mars Analog Environments. ASTROBIOLOGY 2017; 17:363-400. [PMID: 28177270 PMCID: PMC5478115 DOI: 10.1089/ast.2016.1627] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This review of material relevant to the Conference on Biosignature Preservation and Detection in Mars Analog Environments summarizes the meeting materials and discussions and is further expanded upon by detailed references to the published literature. From this diverse source material, there is a detailed discussion on the habitability and biosignature preservation potential of five primary analog environments: hydrothermal spring systems, subaqueous environments, subaerial environments, subsurface environments, and iron-rich systems. Within the context of exploring past habitable environments on Mars, challenges common to all of these key environments are laid out, followed by a focused discussion for each environment regarding challenges to orbital and ground-based observations and sample selection. This leads into a short section on how these challenges could influence our strategies and priorities for the astrobiological exploration of Mars. Finally, a listing of urgent needs and future research highlights key elements such as development of instrumentation as well as continued exploration into how Mars may have evolved differently from Earth and what that might mean for biosignature preservation and detection. Key Words: Biosignature preservation-Biosignature detection-Mars analog environments-Conference report-Astrobiological exploration. Astrobiology 17, 363-400.
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Affiliation(s)
- Lindsay E. Hays
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
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31
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Harrison JP, Angel R, Cockell CS. Astrobiology as a framework for investigating antibiotic susceptibility: a study of Halomonas hydrothermalis. J R Soc Interface 2017; 14:20160942. [PMID: 28123098 PMCID: PMC5310740 DOI: 10.1098/rsif.2016.0942] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 12/14/2016] [Indexed: 01/19/2023] Open
Abstract
Physical and chemical boundaries for microbial multiplication on Earth are strongly influenced by interactions between environmental extremes. However, little is known about how interactions between multiple stress parameters affect the sensitivity of microorganisms to antibiotics. Here, we assessed how 12 distinct permutations of salinity, availability of an essential nutrient (iron) and atmospheric composition (aerobic or microaerobic) affect the susceptibility of a polyextremotolerant bacterium, Halomonas hydrothermalis, to ampicillin, kanamycin and ofloxacin. While salinity had a significant impact on sensitivity to all three antibiotics (as shown by turbidimetric analyses), the nature of this impact was modified by iron availability and the ambient gas composition, with differing effects observed for each compound. These two parameters were found to be of particular importance when considered in combination and, in the case of ampicillin, had a stronger combined influence on antibiotic tolerance than salinity. Our data show how investigating microbial responses to multiple extremes, which are more representative of natural habitats than single extremes, can improve our understanding of the effects of antimicrobial compounds and suggest how studies of habitability, motivated by the desire to map the limits of life, can be used to systematically assess the effectiveness of antibiotics.
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Affiliation(s)
- Jesse P Harrison
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, UK
- Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research Network 'Chemistry Meets Microbiology', University of Vienna, Vienna 1090, Austria
| | - Roey Angel
- Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research Network 'Chemistry Meets Microbiology', University of Vienna, Vienna 1090, Austria
| | - Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, UK
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32
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Enright AML, Ferris FG. Fluctuation Analysis of Redox Potential to Distinguish Microbial Fe(II) Oxidation. ASTROBIOLOGY 2016; 16:846-852. [PMID: 27827533 DOI: 10.1089/ast.2016.1509] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We developed a novel method for distinguishing abiotic and biological iron oxidation in liquid media using oxidation-reduction (redox) potential time series data. The instrument and processing algorithm were tested by immersing the tip of a Pt electrode with an Ag-AgCl reference electrode into an active iron-oxidizing biofilm in a groundwater discharge zone, as well as in two abiotic systems: a killed sample and a chemical control from the same site. We used detrended fluctuation analysis to characterize average root mean square fluctuation behavior, which was distinct in the live system. The calculated α value scaling exponents determined by detrended fluctuation analysis were significantly different at p < 0.001. This indicates that time series of electrode response data may be used to distinguish live and abiotic chemical reaction pathways. Due to the simplicity, portability, and small size, it may be suitable for characterization of extraterrestrial environments where water has been observed, such as Mars and Europa. Key Words: Oxidation-reduction potential-Detrended fluctuation analysis-Iron-oxidizing bacteria. Astrobiology 16, 846-852.
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Affiliation(s)
- A M L Enright
- Department of Earth Sciences, University of Toronto , Toronto, Canada
| | - F G Ferris
- Department of Earth Sciences, University of Toronto , Toronto, Canada
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33
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Domagal-Goldman SD, Wright KE, Adamala K, Arina de la Rubia L, Bond J, Dartnell LR, Goldman AD, Lynch K, Naud ME, Paulino-Lima IG, Singer K, Walther-Antonio M, Abrevaya XC, Anderson R, Arney G, Atri D, Azúa-Bustos A, Bowman JS, Brazelton WJ, Brennecka GA, Carns R, Chopra A, Colangelo-Lillis J, Crockett CJ, DeMarines J, Frank EA, Frantz C, de la Fuente E, Galante D, Glass J, Gleeson D, Glein CR, Goldblatt C, Horak R, Horodyskyj L, Kaçar B, Kereszturi A, Knowles E, Mayeur P, McGlynn S, Miguel Y, Montgomery M, Neish C, Noack L, Rugheimer S, Stüeken EE, Tamez-Hidalgo P, Imari Walker S, Wong T. The Astrobiology Primer v2.0. ASTROBIOLOGY 2016; 16:561-653. [PMID: 27532777 PMCID: PMC5008114 DOI: 10.1089/ast.2015.1460] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 06/06/2016] [Indexed: 05/09/2023]
Affiliation(s)
- Shawn D Domagal-Goldman
- 1 NASA Goddard Space Flight Center , Greenbelt, Maryland, USA
- 2 Virtual Planetary Laboratory , Seattle, Washington, USA
| | - Katherine E Wright
- 3 University of Colorado at Boulder , Colorado, USA
- 4 Present address: UK Space Agency, UK
| | - Katarzyna Adamala
- 5 Department of Genetics, Cell Biology and Development, University of Minnesota , Minneapolis, Minnesota, USA
| | | | - Jade Bond
- 7 Department of Physics, University of New South Wales , Sydney, Australia
| | | | | | - Kennda Lynch
- 10 Division of Biological Sciences, University of Montana , Missoula, Montana, USA
| | - Marie-Eve Naud
- 11 Institute for research on exoplanets (iREx) , Université de Montréal, Montréal, Canada
| | - Ivan G Paulino-Lima
- 12 Universities Space Research Association , Mountain View, California, USA
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
| | - Kelsi Singer
- 14 Southwest Research Institute , Boulder, Colorado, USA
| | | | - Ximena C Abrevaya
- 16 Instituto de Astronomía y Física del Espacio (IAFE) , UBA-CONICET, Ciudad Autónoma de Buenos Aires, Argentina
| | - Rika Anderson
- 17 Department of Biology, Carleton College , Northfield, Minnesota, USA
| | - Giada Arney
- 18 University of Washington Astronomy Department and Astrobiology Program , Seattle, Washington, USA
| | - Dimitra Atri
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
| | | | - Jeff S Bowman
- 19 Lamont-Doherty Earth Observatory, Columbia University , Palisades, New York, USA
| | | | | | - Regina Carns
- 22 Polar Science Center, Applied Physics Laboratory, University of Washington , Seattle, Washington, USA
| | - Aditya Chopra
- 23 Planetary Science Institute, Research School of Earth Sciences, Research School of Astronomy and Astrophysics, The Australian National University , Canberra, Australia
| | - Jesse Colangelo-Lillis
- 24 Earth and Planetary Science, McGill University , and the McGill Space Institute, Montréal, Canada
| | | | - Julia DeMarines
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
| | | | - Carie Frantz
- 27 Department of Geosciences, Weber State University , Ogden, Utah, USA
| | - Eduardo de la Fuente
- 28 IAM-Departamento de Fisica, CUCEI , Universidad de Guadalajara, Guadalajara, México
| | - Douglas Galante
- 29 Brazilian Synchrotron Light Laboratory , Campinas, Brazil
| | - Jennifer Glass
- 30 School of Earth and Atmospheric Sciences, Georgia Institute of Technology , Atlanta, Georgia , USA
| | | | | | - Colin Goldblatt
- 33 School of Earth and Ocean Sciences, University of Victoria , Victoria, Canada
| | - Rachel Horak
- 34 American Society for Microbiology , Washington, DC, USA
| | | | - Betül Kaçar
- 36 Harvard University , Organismic and Evolutionary Biology, Cambridge, Massachusetts, USA
| | - Akos Kereszturi
- 37 Research Centre for Astronomy and Earth Sciences , Hungarian Academy of Sciences, Budapest, Hungary
| | - Emily Knowles
- 38 Johnson & Wales University , Denver, Colorado, USA
| | - Paul Mayeur
- 39 Rensselaer Polytechnic Institute , Troy, New York, USA
| | - Shawn McGlynn
- 40 Earth Life Science Institute, Tokyo Institute of Technology , Tokyo, Japan
| | - Yamila Miguel
- 41 Laboratoire Lagrange, UMR 7293, Université Nice Sophia Antipolis , CNRS, Observatoire de la Côte d'Azur, Nice, France
| | | | - Catherine Neish
- 43 Department of Earth Sciences, The University of Western Ontario , London, Canada
| | - Lena Noack
- 44 Royal Observatory of Belgium , Brussels, Belgium
| | - Sarah Rugheimer
- 45 Department of Astronomy, Harvard University , Cambridge, Massachusetts, USA
- 46 University of St. Andrews , St. Andrews, UK
| | - Eva E Stüeken
- 47 University of Washington , Seattle, Washington, USA
- 48 University of California , Riverside, California, USA
| | | | - Sara Imari Walker
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
- 50 School of Earth and Space Exploration and Beyond Center for Fundamental Concepts in Science, Arizona State University , Tempe, Arizona, USA
| | - Teresa Wong
- 51 Department of Earth and Planetary Sciences, Washington University in St. Louis , St. Louis, Missouri, USA
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Harrison JP, Dobinson L, Freeman K, McKenzie R, Wyllie D, Nixon SL, Cockell CS. Aerobically respiring prokaryotic strains exhibit a broader temperature-pH-salinity space for cell division than anaerobically respiring and fermentative strains. J R Soc Interface 2016; 12:0658. [PMID: 26354829 DOI: 10.1098/rsif.2015.0658] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Biological processes on the Earth operate within a parameter space that is constrained by physical and chemical extremes. Aerobic respiration can result in adenosine triphosphate yields up to over an order of magnitude higher than those attained anaerobically and, under certain conditions, may enable microbial multiplication over a broader range of extremes than other modes of catabolism. We employed growth data published for 241 prokaryotic strains to compare temperature, pH and salinity values for cell division between aerobically and anaerobically metabolizing taxa. Isolates employing oxygen as the terminal electron acceptor exhibited a considerably more extensive three-dimensional phase space for cell division (90% of the total volume) than taxa using other inorganic substrates or organic compounds as the electron acceptor (15% and 28% of the total volume, respectively), with all groups differing in their growth characteristics. Understanding the mechanistic basis of these differences will require integration of research into microbial ecology, physiology and energetics, with a focus on global-scale processes. Critical knowledge gaps include the combined impacts of diverse stress parameters on Gibbs energy yields and rates of microbial activity, interactions between cellular energetics and adaptations to extremes, and relating laboratory-based data to in situ limits for cell division.
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Affiliation(s)
- Jesse P Harrison
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, King's Buildings, Edinburgh EH9 3FD, UK
| | - Luke Dobinson
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, King's Buildings, Edinburgh EH9 3FD, UK
| | - Kenneth Freeman
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, King's Buildings, Edinburgh EH9 3FD, UK
| | - Ross McKenzie
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, King's Buildings, Edinburgh EH9 3FD, UK
| | - Dale Wyllie
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, King's Buildings, Edinburgh EH9 3FD, UK
| | - Sophie L Nixon
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, King's Buildings, Edinburgh EH9 3FD, UK
| | - Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, King's Buildings, Edinburgh EH9 3FD, UK
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35
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Urschel MR, Hamilton TL, Roden EE, Boyd ES. Substrate preference, uptake kinetics and bioenergetics in a facultatively autotrophic, thermoacidophilic crenarchaeote. FEMS Microbiol Ecol 2016; 92:fiw069. [PMID: 27037359 DOI: 10.1093/femsec/fiw069] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/28/2016] [Indexed: 11/12/2022] Open
Abstract
Facultative autotrophs are abundant components of communities inhabiting geothermal springs. However, the influence of uptake kinetics and energetics on preference for substrates is not well understood in this group of organisms. Here, we report the isolation of a facultatively autotrophic crenarchaeote, strain CP80, from Cinder Pool (CP, 88.7°C, pH 4.0), Yellowstone National Park. The 16S rRNA gene sequence from CP80 is 98.8% identical to that from Thermoproteus uzonensis and is identical to the most abundant sequence identified in CP sediments. Strain CP80 reduces elemental sulfur (S8°) and demonstrates hydrogen (H2)-dependent autotrophic growth. H2-dependent autotrophic activity is suppressed by amendment with formate at a concentration in the range of 20-40 μM, similar to the affinity constant determined for formate utilization. Synthesis of a cell during growth with low concentrations of formate required 0.5 μJ compared to 2.5 μJ during autotrophic growth with H2 These results, coupled to data indicating greater C assimilation efficiency when grown with formate as compared to carbon dioxide, are consistent with preferential use of formate for energetic reasons. Collectively, these results provide new insights into the kinetic and energetic factors that influence the physiology and ecology of facultative autotrophs in high-temperature acidic environments.
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Affiliation(s)
- Matthew R Urschel
- Department of Microbiology and Immunology and the Thermal Biology Institute, Montana State University, Bozeman, MT 59717, USA
| | - Trinity L Hamilton
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Eric E Roden
- Department of Geosciences, University of Wisconsin, Madison, WI 53706, USA NASA Astrobiology Institute, Ames Research Center, Moffett Field, CA 94035, USA
| | - Eric S Boyd
- Department of Microbiology and Immunology and the Thermal Biology Institute, Montana State University, Bozeman, MT 59717, USA NASA Astrobiology Institute, Ames Research Center, Moffett Field, CA 94035, USA
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Horneck G, Walter N, Westall F, Grenfell JL, Martin WF, Gomez F, Leuko S, Lee N, Onofri S, Tsiganis K, Saladino R, Pilat-Lohinger E, Palomba E, Harrison J, Rull F, Muller C, Strazzulla G, Brucato JR, Rettberg P, Capria MT. AstRoMap European Astrobiology Roadmap. ASTROBIOLOGY 2016; 16:201-43. [PMID: 27003862 PMCID: PMC4834528 DOI: 10.1089/ast.2015.1441] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 01/27/2016] [Indexed: 05/07/2023]
Abstract
The European AstRoMap project (supported by the European Commission Seventh Framework Programme) surveyed the state of the art of astrobiology in Europe and beyond and produced the first European roadmap for astrobiology research. In the context of this roadmap, astrobiology is understood as the study of the origin, evolution, and distribution of life in the context of cosmic evolution; this includes habitability in the Solar System and beyond. The AstRoMap Roadmap identifies five research topics, specifies several key scientific objectives for each topic, and suggests ways to achieve all the objectives. The five AstRoMap Research Topics are • Research Topic 1: Origin and Evolution of Planetary Systems • Research Topic 2: Origins of Organic Compounds in Space • Research Topic 3: Rock-Water-Carbon Interactions, Organic Synthesis on Earth, and Steps to Life • Research Topic 4: Life and Habitability • Research Topic 5: Biosignatures as Facilitating Life Detection It is strongly recommended that steps be taken towards the definition and implementation of a European Astrobiology Platform (or Institute) to streamline and optimize the scientific return by using a coordinated infrastructure and funding system.
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Affiliation(s)
- Gerda Horneck
- European Astrobiology Network Association
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Köln, Germany
| | | | - Frances Westall
- Centre National de la Recherche Scientifique–Centre de Biophysique Moléculaire, Orleans, France
| | - John Lee Grenfell
- Institute for Planetary Research, German Aerospace Center (DLR), Berlin, Germany
| | - William F. Martin
- Institute of Molecular Evolution, Heinrich-Heine University of Düsseldorf, Düsseldorf, Germany
| | - Felipe Gomez
- INTA Centre for Astrobiology, Torrejón de Ardoz, Madrid, Spain
| | - Stefan Leuko
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Köln, Germany
| | - Natuschka Lee
- Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden
- Department of Microbiology, Technical University München, München, Germany
| | - Silvano Onofri
- Department of Ecological and Biological Sciences, University of Tuscia, Viterbo, Italy
| | - Kleomenis Tsiganis
- Department of Physics, Section of Astrophysics, Astronomy and Mechanics, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Raffaele Saladino
- Department of Agrobiology and Agrochemistry, University of Tuscia, Viterbo, Italy
| | | | - Ernesto Palomba
- INAF–Institute for Space Astrophysics and Planetology, Rome, Italy
| | - Jesse Harrison
- Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria
| | - Fernando Rull
- Department of Condensed Matter Physics, Crystallography and Mineralogy, Valladolid University, Valladolid, Spain
| | | | | | | | - Petra Rettberg
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Köln, Germany
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Cockell CS, Bush T, Bryce C, Direito S, Fox-Powell M, Harrison JP, Lammer H, Landenmark H, Martin-Torres J, Nicholson N, Noack L, O'Malley-James J, Payler SJ, Rushby A, Samuels T, Schwendner P, Wadsworth J, Zorzano MP. Habitability: A Review. ASTROBIOLOGY 2016; 16:89-117. [PMID: 26741054 DOI: 10.1089/ast.2015.1295] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Habitability is a widely used word in the geoscience, planetary science, and astrobiology literature, but what does it mean? In this review on habitability, we define it as the ability of an environment to support the activity of at least one known organism. We adopt a binary definition of "habitability" and a "habitable environment." An environment either can or cannot sustain a given organism. However, environments such as entire planets might be capable of supporting more or less species diversity or biomass compared with that of Earth. A clarity in understanding habitability can be obtained by defining instantaneous habitability as the conditions at any given time in a given environment required to sustain the activity of at least one known organism, and continuous planetary habitability as the capacity of a planetary body to sustain habitable conditions on some areas of its surface or within its interior over geological timescales. We also distinguish between surface liquid water worlds (such as Earth) that can sustain liquid water on their surfaces and interior liquid water worlds, such as icy moons and terrestrial-type rocky planets with liquid water only in their interiors. This distinction is important since, while the former can potentially sustain habitable conditions for oxygenic photosynthesis that leads to the rise of atmospheric oxygen and potentially complex multicellularity and intelligence over geological timescales, the latter are unlikely to. Habitable environments do not need to contain life. Although the decoupling of habitability and the presence of life may be rare on Earth, it may be important for understanding the habitability of other planetary bodies.
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Affiliation(s)
- C S Cockell
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - T Bush
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - C Bryce
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - S Direito
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - M Fox-Powell
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - J P Harrison
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - H Lammer
- 2 Austrian Academy of Sciences, Space Research Institute , Graz, Austria
| | - H Landenmark
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - J Martin-Torres
- 3 Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology , Kiruna, Sweden; and Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Granada, Spain
| | - N Nicholson
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - L Noack
- 4 Department of Reference Systems and Planetology, Royal Observatory of Belgium , Brussels, Belgium
| | - J O'Malley-James
- 5 School of Physics and Astronomy, University of St Andrews , St Andrews, UK; now at the Carl Sagan Institute, Cornell University, Ithaca, NY, USA
| | - S J Payler
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - A Rushby
- 6 Centre for Ocean and Atmospheric Science (COAS), School of Environmental Sciences, University of East Anglia , Norwich, UK
| | - T Samuels
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - P Schwendner
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - J Wadsworth
- 1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
| | - M P Zorzano
- 3 Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology , Kiruna, Sweden; and Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Granada, Spain
- 7 Centro de Astrobiología (CSIC-INTA) , Torrejón de Ardoz, Madrid, Spain
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Marlow JJ, Larowe DE, Ehlmann BL, Amend JP, Orphan VJ. The potential for biologically catalyzed anaerobic methane oxidation on ancient Mars. ASTROBIOLOGY 2014; 14:292-307. [PMID: 24684241 DOI: 10.1089/ast.2013.1078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
This study examines the potential for the biologically mediated anaerobic oxidation of methane (AOM) coupled to sulfate reduction on ancient Mars. Seven distinct fluids representative of putative martian groundwater were used to calculate Gibbs energy values in the presence of dissolved methane under a range of atmospheric CO2 partial pressures. In all scenarios, AOM is exergonic, ranging from -31 to -135 kJ/mol CH4. A reaction transport model was constructed to examine how environmentally relevant parameters such as advection velocity, reactant concentrations, and biomass production rate affect the spatial and temporal dependences of AOM reaction rates. Two geologically supported models for ancient martian AOM are presented: a sulfate-rich groundwater with methane produced from serpentinization by-products, and acid-sulfate fluids with methane from basalt alteration. The simulations presented in this study indicate that AOM could have been a feasible metabolism on ancient Mars, and fossil or isotopic evidence of this metabolic pathway may persist beneath the surface and in surface exposures of eroded ancient terrains.
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Affiliation(s)
- Jeffrey J Marlow
- 1 Division of Geological and Planetary Sciences, California Institute of Technology , Pasadena, California
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Cockell CS. Trajectories of martian habitability. ASTROBIOLOGY 2014; 14:182-203. [PMID: 24506485 PMCID: PMC3929387 DOI: 10.1089/ast.2013.1106] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/29/2013] [Indexed: 05/21/2023]
Abstract
Beginning from two plausible starting points-an uninhabited or inhabited Mars-this paper discusses the possible trajectories of martian habitability over time. On an uninhabited Mars, the trajectories follow paths determined by the abundance of uninhabitable environments and uninhabited habitats. On an inhabited Mars, the addition of a third environment type, inhabited habitats, results in other trajectories, including ones where the planet remains inhabited today or others where planetary-scale life extinction occurs. By identifying different trajectories of habitability, corresponding hypotheses can be described that allow for the various trajectories to be disentangled and ultimately a determination of which trajectory Mars has taken and the changing relative abundance of its constituent environments.
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Affiliation(s)
- Charles S Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh , Edinburgh, UK
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Boyd ES, Hamilton TL, Wang J, He L, Zhang CL. The role of tetraether lipid composition in the adaptation of thermophilic archaea to acidity. Front Microbiol 2013; 4:62. [PMID: 23565112 PMCID: PMC3615187 DOI: 10.3389/fmicb.2013.00062] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Accepted: 03/04/2013] [Indexed: 01/10/2023] Open
Abstract
Diether and tetraether lipids are fundamental components of the archaeal cell membrane. Archaea adjust the degree of tetraether lipid cyclization in order to maintain functional membranes and cellular homeostasis when confronted with pH and/or thermal stress. Thus, the ability to adjust tetraether lipid composition likely represents a critical phenotypic trait that enabled archaeal diversification into environments characterized by extremes in pH and/or temperature. Here we assess the relationship between geochemical variation, core- and polar-isoprenoid glycerol dibiphytanyl glycerol tetraether (C-iGDGT and P-iGDGT, respectively) lipid composition, and archaeal 16S rRNA gene diversity and abundance in 27 geothermal springs in Yellowstone National Park, Wyoming. The composition and abundance of C-iGDGT and P-iGDGT lipids recovered from geothermal ecosystems were distinct from surrounding soils, indicating that they are synthesized endogenously. With the exception of GDGT-0 (no cyclopentyl rings), the abundances of individual C-iGDGT and P-iGDGT lipids were significantly correlated. The abundance of a number of individual tetraether lipids varied positively with the relative abundance of individual 16S rRNA gene sequences, most notably crenarchaeol in both the core and polar GDGT fraction and sequences closely affiliated with Candidatus Nitrosocaldus yellowstonii. This finding supports the proposal that crenarchaeol is a biomarker for nitrifying archaea. Variation in the degree of cyclization of C- and P-iGDGT lipids recovered from geothermal mats and sediments could best be explained by variation in spring pH, with lipids from acidic environments tending to have, on average, more internal cyclic rings than those from higher pH ecosystems. Likewise, variation in the phylogenetic composition of archaeal 16S rRNA genes could best be explained by spring pH. In turn, the phylogenetic similarity of archaeal 16S rRNA genes was significantly correlated with the similarity in the composition of C- and P-iGDGT lipids. Taken together, these data suggest that the ability to adjust the composition of GDGT lipid membranes played a central role in the diversification of archaea into or out of environments characterized by extremes of low pH and high temperature.
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Affiliation(s)
- Eric S Boyd
- Department of Chemistry and Biochemistry, Montana State University Bozeman, MT, USA
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41
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Tiago I, Veríssimo A. Microbial and functional diversity of a subterrestrial high pH groundwater associated to serpentinization. Environ Microbiol 2012; 15:1687-706. [PMID: 23731249 DOI: 10.1111/1462-2920.12034] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 10/25/2012] [Indexed: 11/27/2022]
Abstract
Microbial and functional diversity were assessed, from a serpentinization-driven subterrestrial alkaline aquifer - Cabeço de Vide Aquifer (CVA) in Portugal. DGGE analyses revealed the presence of a stable microbial community. By 16S rRNA gene libraries and pyrosequencing analyses, a diverse bacterial composition was determined, contrasting with low archaeal diversity. Within Bacteria the majority of the populations were related to organisms or sequences affiliated to class Clostridia, but members of classes Acidobacteria, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Deinococci, Gammaproteobacteria and of the phyla Bacteroidetes, Chloroflexi and Nitrospira were also detected. Domain Archaea encompassed mainly sequences affiliated to Euryarchaeota. Only form I RuBisCO - cbbL was detected. Autotrophic carbon fixation via the rTCA, 3-HP and 3-HP/4H-B cycles could not be confirmed. The detected APS reductase alpha subunit - aprA sequences were phylogenetically related to sequences of sulfate-reducing bacteria belonging to Clostridia, and also to sequences of chemolithoautothrophic sulfur-oxidizing bacteria belonging to Betaproteobacteria. Sequences of methyl coenzyme M reductase - mcrA were phylogenetically affiliated to sequences belonging to Anaerobic Methanotroph group 1 (ANME-1). The populations found and the functional key markers detected in CVA suggest that metabolisms related to H2 , methane and/or sulfur may be the major driving forces in this environment.
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Affiliation(s)
- Igor Tiago
- Department of Life Sciences, University of Coimbra, Apartado 3046, 3001-401 Coimbra, Portugal
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42
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Boyd ES, Fecteau KM, Havig JR, Shock EL, Peters JW. Modeling the habitat range of phototrophs in yellowstone national park: toward the development of a comprehensive fitness landscape. Front Microbiol 2012; 3:221. [PMID: 22719737 PMCID: PMC3376417 DOI: 10.3389/fmicb.2012.00221] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 05/30/2012] [Indexed: 01/10/2023] Open
Abstract
The extent to which geochemical variation shapes the distribution of phototrophic metabolisms was modeled based on 439 observations in geothermal springs in Yellowstone National Park (YNP), Wyoming. Generalized additive models (GAMs) were developed to predict the distribution of phototrophic metabolism as a function of spring temperature, pH, and total sulfide. GAMs comprised of temperature explained 38.8% of the variation in the distribution of phototrophic metabolism, whereas GAMs comprised of sulfide and pH explained 19.6 and 11.2% of the variation, respectively. These results suggest that of the measured variables, temperature is the primary constraint on the distribution of phototrophs in YNP. GAMs comprised of multiple variables explained a larger percentage of the variation in the distribution of phototrophic metabolism, indicating additive interactions among variables. A GAM that combined temperature and sulfide explained the greatest variation in the dataset (53.4%) while minimizing the introduction of degrees of freedom. In an effort to verify the extent to which phototroph distribution reflects constraints on activity, we examined the influence of sulfide and temperature on dissolved inorganic carbon (DIC) uptake rates under both light and dark conditions. Light-driven DIC uptake decreased systematically with increasing concentrations of sulfide in acidic, algal-dominated systems, but was unaffected in alkaline, cyanobacterial-dominated systems. In both alkaline and acidic systems, light-driven DIC uptake was suppressed in cultures incubated at temperatures 10°C greater than their in situ temperature. Collectively, these quantitative results indicate that apart from light availability, the habitat range of phototrophs in YNP springs is defined largely by constraints imposed firstly by temperature and secondly by sulfide on the activity of these populations that inhabit the edges of the habitat range. These findings are consistent with the predictions from GAMs and provide a quantitative framework from which to translate distributional patterns into fitness landscapes for use in interpreting the environmental constraints that have shaped the evolution of this process through Earth history.
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Affiliation(s)
- Eric S. Boyd
- Department of Chemistry and Biochemistry, Astrobiology Biogeocatalysis Research Center, Montana State UniversityBozeman, MT, USA
| | | | - Jeff R. Havig
- School of Earth and Space Exploration, Arizona State UniversityTempe, AZ, USA
| | - Everett L. Shock
- Department of Chemistry and Biochemistry, Arizona State UniversityTempe, AZ, USA
- School of Earth and Space Exploration, Arizona State UniversityTempe, AZ, USA
| | - John W. Peters
- Department of Chemistry and Biochemistry, Astrobiology Biogeocatalysis Research Center, Montana State UniversityBozeman, MT, USA
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Pascal R, Boiteau L. Energy flows, metabolism and translation. Philos Trans R Soc Lond B Biol Sci 2012; 366:2949-58. [PMID: 21930587 DOI: 10.1098/rstb.2011.0135] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Thermodynamics provides an essential approach to understanding how living organisms survive in an organized state despite the second law. Exchanges with the environment constantly produce large amounts of entropy compensating for their own organized state. In addition to this constraint on self-organization, the free energy delivered to the system, in terms of potential, is essential to understand how a complex chemistry based on carbon has emerged. Accordingly, the amount of free energy brought about through discrete events must reach the strength needed to induce chemical changes in which covalent bonds are reorganized. The consequence of this constraint was scrutinized in relation to both the development of a carbon metabolism and that of translation. Amino acyl adenylates involved as aminoacylation intermediates of the latter process reach one of the higher free energy levels found in biochemistry, which may be informative on the range in which energy was exchanged in essential early biochemical processes. The consistency of this range with the amount of energy needed to weaken covalent bonds involving carbon may not be accidental but the consequence of the above mentioned thermodynamic constraints. This could be useful in building scenarios for the emergence and early development of translation.
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Affiliation(s)
- Robert Pascal
- Institut des Biomolécules Max Mousseron (IBMM), UMR 5247, Université Montpellier 1 and 2, 34095 Montpellier Cedex 5, France.
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Orcutt BN, Sylvan JB, Knab NJ, Edwards KJ. Microbial ecology of the dark ocean above, at, and below the seafloor. Microbiol Mol Biol Rev 2011; 75:361-422. [PMID: 21646433 PMCID: PMC3122624 DOI: 10.1128/mmbr.00039-10] [Citation(s) in RCA: 324] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The majority of life on Earth--notably, microbial life--occurs in places that do not receive sunlight, with the habitats of the oceans being the largest of these reservoirs. Sunlight penetrates only a few tens to hundreds of meters into the ocean, resulting in large-scale microbial ecosystems that function in the dark. Our knowledge of microbial processes in the dark ocean-the aphotic pelagic ocean, sediments, oceanic crust, hydrothermal vents, etc.-has increased substantially in recent decades. Studies that try to decipher the activity of microorganisms in the dark ocean, where we cannot easily observe them, are yielding paradigm-shifting discoveries that are fundamentally changing our understanding of the role of the dark ocean in the global Earth system and its biogeochemical cycles. New generations of researchers and experimental tools have emerged, in the last decade in particular, owing to dedicated research programs to explore the dark ocean biosphere. This review focuses on our current understanding of microbiology in the dark ocean, outlining salient features of various habitats and discussing known and still unexplored types of microbial metabolism and their consequences in global biogeochemical cycling. We also focus on patterns of microbial diversity in the dark ocean and on processes and communities that are characteristic of the different habitats.
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Affiliation(s)
- Beth N. Orcutt
- Center for Geomicrobiology, Aarhus University, 8000 Aarhus, Denmark
- Marine Environmental Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089
| | - Jason B. Sylvan
- Marine Environmental Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089
| | - Nina J. Knab
- Marine Environmental Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089
| | - Katrina J. Edwards
- Marine Environmental Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089
- Department of Earth Sciences, University of Southern California, Los Angeles, California 90089
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Boiteau L, Pascal R. Energy sources, self-organization, and the origin of life. ORIGINS LIFE EVOL B 2011; 41:23-33. [PMID: 20333546 DOI: 10.1007/s11084-010-9209-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 03/05/2010] [Indexed: 10/19/2022]
Abstract
The emergence and early developments of life are considered from the point of view that contingent events that inevitably marked evolution were accompanied by deterministic driving forces governing the selection between different alternatives. Accordingly, potential energy sources are considered for their propensity to induce self-organization within the scope of the chemical approach to the origin of life. Requirements in terms of quality of energy locate thermal or photochemical activation in the atmosphere as highly likely processes for the formation of activated low-molecular weight organic compounds prone to induce biomolecular self-organization through their ability to deliver quanta of energy matching the needs of early biochemical pathways or the reproduction of self-replicating entities. These lines of reasoning suggest the existence of a direct connection between the free energy content of intermediates of early pathways and the quanta of energy delivered by available sources of energy.
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Affiliation(s)
- Laurent Boiteau
- Institut des Biomolécules Max Mousseron, UMR 5247, Universités Montpellier 1 & Montpellier 2-CNRS, CC DSBC 1706-Université Montpellier 2, Place Eugène Bataillon, 34095, Montpellier Cedex 5, France
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Houghton JL, Seyfried WE. An experimental and theoretical approach to determining linkages between geochemical variability and microbial biodiversity in seafloor hydrothermal chimneys. GEOBIOLOGY 2010; 8:457-470. [PMID: 20726900 DOI: 10.1111/j.1472-4669.2010.00255.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
New experimental results of fluid-mineral reactions at hydrothermal conditions relevant to life demonstrate that key redox reactions involving iron, sulfur, and hydrogen remain at disequilibrium at 100 °C, even in a heterogeneous system and thus are energetically favorable for microbial metabolism. Predictions from geochemical models utilizing the experimental results and specific to two contrasting case studies from the East Pacific Rise were statistically characterized and correlated to the energetics of redox reactions available for intra-chimney microbial populations. In general, predictions of available energy for autotrophic metabolism are largely similar between the mature and the nascent chimneys, although important differences still exist. Metabolic processes predicted by energetics exhibit the same trends observed in the field data for the mature chimney, but overestimate the diversity observed in the nascent chimney. Several combinations of redox reaction pairs are predicted to support mixed consortia, while some combinations appear to favor more versatile microbes capable of utilizing several reactions under rapidly changing environmental conditions within chimney walls. In addition, conditions favorable to elemental sulfur reduction and methanogenesis exhibit a negative control on the diversity of microbial populations within these chimney walls, whereas H₂S oxidation, elemental sulfur oxidation and the knallgas reaction are positively correlated with both abundance and diversity of micro-organisms. Coupling field observations of both microbial diversity and geochemical heterogeneity with lab-based experimental and theoretical modeling can facilitate translation of the observed genetic diversity into physiological diversity, thus enhancing understanding of linked phenomena of microbially induced biogeochemical transformations in complex heterogeneous systems.
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Affiliation(s)
- J L Houghton
- Department of Biology, Rhodes College, Memphis, TN, USA.
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47
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Two rovers to the same site on Mars, 2018: possibilities for cooperative science. ASTROBIOLOGY 2010; 10:663-685. [PMID: 20932131 DOI: 10.1089/ast.2010.0526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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The Mars Astrobiology Explorer-Cacher (MAX-C): a potential rover mission for 2018. Final report of the Mars Mid-Range Rover Science Analysis Group (MRR-SAG) October 14, 2009. ASTROBIOLOGY 2010; 10:127-163. [PMID: 20298148 DOI: 10.1089/ast.2010.0462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
This report documents the work of the Mid-Range Rover Science Analysis Group (MRR-SAG), which was assigned to formulate a concept for a potential rover mission that could be launched to Mars in 2018. Based on programmatic and engineering considerations as of April 2009, our deliberations assumed that the potential mission would use the Mars Science Laboratory (MSL) sky-crane landing system and include a single solar-powered rover. The mission would also have a targeting accuracy of approximately 7 km (semimajor axis landing ellipse), a mobility range of at least 10 km, and a lifetime on the martian surface of at least 1 Earth year. An additional key consideration, given recently declining budgets and cost growth issues with MSL, is that the proposed rover must have lower cost and cost risk than those of MSL--this is an essential consideration for the Mars Exploration Program Analysis Group (MEPAG). The MRR-SAG was asked to formulate a mission concept that would address two general objectives: (1) conduct high priority in situ science and (2) make concrete steps toward the potential return of samples to Earth. The proposed means of achieving these two goals while balancing the trade-offs between them are described here in detail. We propose the name Mars Astrobiology Explorer-Cacher(MAX-C) to reflect the dual purpose of this potential 2018 rover mission.
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Abstract
The rocks and sediments of the oceanic subsurface represent a diverse mosaic of environments potentially inhabited by microorganisms. Understanding microbial ecosystems in subseafloor environments confounds standard ecological descriptions in part because we have difficulty elucidating and describing the scale of relevant processes. Habitat characteristics impact microbial activities and growth, which in turn affect microbial diversity, net production, and global biogeochemical cycles. Herein we provide descriptions of subseafloor microbial provinces, broadly defined as geologically and geographically coherent regions of the subseafloor that may serve as potential microbial habitats. The purpose of this review is to summarize and refine criteria for the definition and delineation of distinct subseafloor microbial habitats to aid in their exploration. This review and the criteria we outline aim to develop a unified framework to improve our understanding of subseafloor microbial ecology, enable quantification of geomicrobial processes, and facilitate their accurate assimilation into biogeochemical models.
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Affiliation(s)
- Matthew O Schrenk
- Department of Biology, East Carolina University, Howell Science Complex, Greenville, North Carolina 27858, USA.
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50
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