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Colón-Santos S, Vázquez-Salazar A, Adams A, Campillo-Balderas JA, Hernández-Morales R, Jácome R, Muñoz-Velasco I, Rodriguez LE, Schaible MJ, Schaible GA, Szeinbaum N, Thweatt JL, Trubl G. Chapter 2: What Is Life? ASTROBIOLOGY 2024; 24:S40-S56. [PMID: 38498820 DOI: 10.1089/ast.2021.0116] [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
The question "What is life?" has existed since the beginning of recorded history. However, the scientific and philosophical contexts of this question have changed and been refined as advancements in technology have revealed both fine details and broad connections in the network of life on Earth. Understanding the framework of the question "What is life?" is central to formulating other questions such as "Where else could life be?" and "How do we search for life elsewhere?" While many of these questions are addressed throughout the Astrobiology Primer 3.0, this chapter gives historical context for defining life, highlights conceptual characteristics shared by all life on Earth as well as key features used to describe it, discusses why it matters for astrobiology, and explores both challenges and opportunities for finding an informative operational definition.
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Affiliation(s)
- Stephanie Colón-Santos
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Wisconsin, USA
- Department of Botany, University of Wisconsin-Madison, Wisconsin, USA
| | - Alberto Vázquez-Salazar
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
- Department of Chemical and Biomolecular Engineering, University of California Los Angeles, California, USA
| | - Alyssa Adams
- Department of Botany, University of Wisconsin-Madison, Wisconsin, USA
| | | | - Ricardo Hernández-Morales
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Rodrigo Jácome
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Israel Muñoz-Velasco
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
- Departamento de Biología Celular, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Laura E Rodriguez
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA
| | - Micah J Schaible
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - George A Schaible
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Nadia Szeinbaum
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana, USA
| | - Jennifer L Thweatt
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, Pennsylvania, USA. (Former)
| | - Gareth Trubl
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
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Tibayrenc M, Ayala FJ. Models in parasite and pathogen evolution: Genomic analysis reveals predominant clonality and progressive evolution at all evolutionary scales in parasitic protozoa, yeasts and bacteria. ADVANCES IN PARASITOLOGY 2021; 111:75-117. [PMID: 33482977 DOI: 10.1016/bs.apar.2020.12.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The predominant clonal evolution (PCE) model of pathogenic microorganisms postulates that the impact of genetic recombination in those pathogens' natural populations is not enough to erase a persistent phylogenetic signal at all evolutionary scales from microevolution till geological times in the whole ecogeographical range of the species considered. We have tested this model with a set of representative parasitic protozoa, yeasts and bacteria in the light of the most recent genomic data. All surveyed species, including those that were considered as highly recombining, exhibit similar PCE patterns above and under the species level, from macro- to micro-evolutionary scales (Russian doll pattern), suggesting gradual evolution. To our knowledge, it is the first time that such a strong common evolutionary feature among very diverse pathogens has been evidenced. The implications of this model for basic biology and applied research are exposed. These implications include our knowledge on the pathogens' reproductive mode, their population structure, the possibility to type strain and to follow up epidemics (molecular epidemiology) and to revisit pathogens' taxonomy through a flexible use of the phylogenetic species concept (Cracraft, 1983).
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Affiliation(s)
- Michel Tibayrenc
- Maladies Infectieuses et Vecteurs Ecologie, Génétique, Evolution et Contrôle, MIVEGEC (IRD 224-CNRS 5290-UM1-UM2), Institut de recherche pour le développement, Montpellier Cedex 5, France.
| | - Francisco J Ayala
- Catedra Francisco Jose Ayala of Science, Technology, and Religion, University of Comillas, Madrid, Spain; 2 Locke Court, Irvine, CA, United States
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