The origin(s) of life - I

Transcription

1 The origin(s) of life - I Carlos Briones Molecular Evolution Laboratory Centro de Astrobiología (CSIC-INTA, Associated to NASA Astrobiology Institute) Madrid, Spain. III AstrobiON - Oct 1-5, 2018 Observatório Nacional, Rio de Janeiro, Brazil

2 OUTLINE The origin(s) of life I - Introduction - The oldest traces of life - The composition of life - What is life? - Classification of life - Towards the origin(s) of life

3 ORIGIN(S) OF LIFE When? How? Chance and/or Necessity? Where? Terrestrial o ET? Once or several times? ( )

4 - 4.6 Gyr

5 Gyr

6 - 4.5 Gyr

7 - 3.8 Gyr

8 HB LHB Origin of the Earth and Moon: 4.57 Gyr Crust and oceans: 4.4 Earth's oldest sedimentary rocks: 3.9 Isotopic fingerprints of early life: 4.1?-3.85 Oldest fossils: 3.7?-3.5 O.V. PRECAMBRIAN HADEAN ARCHAEAN PROTEROZOIC PHAN. t Gyr 0

9 TWO COMPLEMENTARY APPROACHES O.V. PRECAMBRIAN HADEAN ARCHAEAN PROTEROZOIC PHAN. t Gyr 0 Bottom-up Past-Present From the non-living Astrochemistry, Geochemistry, Prebiotic chemistry, Synthetic chemistry Top-down Present-Past From the living Palaeontology, Microbiology, Phylogenetics, Minimal cell models

10 EARLY EARTH: A GLOBAL LABORATORY Gyr [Cleaves (2013), Life]

11 - 3.8 Gyr [Briones, Fernández Soto and Bermúdez de Castro, Orígenes, Ed. Crítica, 2015]

12

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14 THE OLDEST TRACES OF LIFE (?) Isotopic signature (or isotopic fingerprint): ratio among different isotopes of particular elements (C, N, O ) in a material (e.g., a rock). In geochemistry, the 13 C/ 12 C ratio is calculated as δ 13 C, with respect to a standard ( PDB : Pee Dee Belemnite, a Cretaceous fossil found in South Carolina, USA, with a very high 13 C/ 12 C ratio of ) δ 13 C informs about the origin of the C present in a material: - Biological processes tend to take up the lower mass isotope ( 12 C) through kinetic fractionation δ 13 C: - 20 to - 35 PDB (up to - 60 in methanotrophs) - Inorganic carbon δ 13 C: + 5 to - 5 PDB (though methane from hydrothermal vents and C from extraterrestrial sources can show δ 13 C ~ biological)

15 THE OLDEST TRACES OF LIFE (?) Isotopic signatures in the oldest rocks on Earth? - Problem: they have been severely metamorphosed. But - Some minerals are relatively resistant against metamorphism (e.g., apatite) The oldest sedimentary rocks on Earth: - The Isua Greenstone Belt (Greenland): Archean greenstone aged between 3.8 and 3.7 Gyr. It contains metamorphosed volcanic and sedimentary rocks Gyr: Carbonaceous inclusions in apatite consist of δ 13 C - 21 to - 49 PDB [Mojzsis et al., 1996] Biological origin? Life emerged at least 3.8 Gyr ago? Gyr: Sedimentary rocks, δ 13 C - 19 PDB [Rosing et al., 1999; Ohomoto et al., 2014]

16 THE OLDEST FOSSILS Stromatolite (Pilbara, Australia, -3.5 Gyr) Microbial mat (present) 4 cm Stromatolite?? (Isua, Greenland, -3.7 Gyr) [Nutman et al. (2016), Nature]

17 100 µm [Dodd et al. (2017), Nature] Hematite tubes (reconstruction) Microbial origin?? (Nuvvuagittuq belt, Quebec, Canada, Ga)

18 Dresser Formation (Pilbara, Ga) Geyserite ( ºC) [Djokic et al. (2017), Nature Comm.]

19 Microfossils (Pilbara, Gyr)??? [Schopf et al. (1993), Science] Cyanobacteria (present) Microfossils (Pilbara, Gyr) [Wacey et al. (2011), Nat. Geosci.] Abiotic biomorph [J.M. García-Ruiz, Spain]

20 THE COMPOSITION OF LIFE

21 C + H + O + N + P + S = 99% mass of organisms

22 COMPOSITION (% mass) CORTEZA TERRESTRE Otros: Other: 2% He: 23% SUN H: 75% Mg: 2% K: 4% Na: 2% Ca: 6% Fe: 10% Al: 9% Si: 36% O: 31% EARTH S CRUST S: 0.3% Otros: Other: 1% 2% P: 1.1% N: 3.2% H: 10.2% C: 18.3% ORGANISMS O: 65.9%

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24 Water - The best solvent - Allows chemical reactions - Active role in molecular processes - Provides thermal stability - Very abundant in the Universe

25 - Allows a complex chemistry based on covalent bonds C Carbon , Different C-C structures: aliphatic: aromatic: - Functional groups with H, O, N, P, S 1s 2 2s 2 2p 2

26 THE MAIN MOLECULES OF LIFE Precursors: H 2 0, NH 3, CO 2, NO... Low MW organic compounds: cofactors, antibiotics, hormones Monomers: nucleotides, aminoacids, sugars, fatty acids DNA RNA Proteins

27 CELLS Procariotic cells (Bacteria + Archaea) Eukaryotic cells (Eucarya) 1 m 1 m

28 WHAT IS LIFE?

29 [Moreira and López-García (2009), Nat. Rev. Microbiol]

30 SOME (OPERATIONAL) DEFINITIONS OF LIFE "Life is a system that can maintain itself in a state far from equilibrium, and that can grow and multiply with the help of a continuous flow of energy and matter from the environment" (C. de Duve, 1991) "Life is a self-sustaining chemical system capable of undergoing Darwinian evolution" (G.F. Joyce, Adopted by NAI) "Living beings are autonomous systems with open-ended evolution capacity" (K. Ruiz-Mirazo et al., 2004) "Nothing makes sense in biology except in the light of evolution (T. Dobzhansky, 1973)

31 Replication Metabolism Compartment LIFE

32 CLASSIFICATION OF LIFE

33 CELLULAR ORGANIZATION

34 GENETICS DNA RNA Proteins

35 METABOLISM

36 Common ancestor?

37 EUCARYA ARCHAEA BACTERIA Last Universal Common Ancestor (LUCA) Origin of life

38 Different genes give different universal phylogenies

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42 TOWARDS THE ORIGIN(S) OF LIFE

43 THE FIRST (SCIENTIFIC) IDEAS There is grandeur in this view of life, with its several powers, having being originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. C.R. Darwin. The Origin of Species (1 st Ed. Nov 24, 1859) But if (and oh, what a big if) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc. present that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed. C.R. Darwin. Letter to J.D. Hooker (Feb 1, 1871)

44 THE FIRST MODELS Oparin s step-wise heterotrophic origin of life Reducing atmosphere Synthesis of organic compounds A.I. Oparin (1924) Formation of the primitive soup Coacervates Primordial heterotrophs J.B.S. Haldane (1929)

45 THE FIRST EXPERIMENTS J. Oró (1960) S.L. Miller (1953)

46 PREBIOTIC CHEMISTRY Miller s Experiment (S. Miller, H. Urey, 1953) H 2 O + H 2 + NH 3 + CH 4 closed system sparks (two weeks later...) aminoacids + other biomonomers

47 Murchison meteorite Fallen in Murchison (Australia), Sept A 4.6 x 10 9 years-old carbonaceous chondrite [Deamer (2011)]

48 Aliphatic amino acids in the Murchison meteorite Murchison meteorite Synthesized in a CH 4 +CO 2 +NH 3 +H 2 O+H 2 S atmosphere [Parker et al. (2011), Science]

49 The prebiotic synthesis of adenine (J. Oró, 1960) Coat of Arms of Marquess of Oró (2003)

50 The chemautotrophic theory CoASH + 8eˉ 2 CO 2 CH 3 COSCoA Two pathways for early C fixation Reverse Citric Acid cycle - Reduction of CO 2 on metal sulfides - Wächtershäuser (1988), Morowitz Wood/Ljungdahl (W-L) pathway - Acetyl-CoA net synthesis - Rusell & Martin Low MW compounds Macromolecules Günter Wächtershäuser Primitive cells Hydrothermal vents

51 [de la Escosura, Briones and Ruiz-Mirazo (2014)]

52 Composition of the primordial soup

53 Were all the ingredients of the soup endogenous? Were some of the ingredients delivered by meteorites/comets?

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55 The prebiotic chemist s dream leads to the molecular biologist s nightmare [Joyce & Orgel, (1999). In The RNA World, 2nd Ed. R.F. Gesteland, T.R. Cech, J.F. Atkins (Eds.). CSHL Press]

56 3.850 t (Ma) B A E - LUCA: modern cellular life DNA / RNA / Proteins / Membranes... - Biomonomers ( primordial soup ) - Precursors: H 2 O, H 2, NH 3, CO 2, SH 2...

57 3.850 t (Ma) B A E MORE THAN ONE ORIGIN?

58 Bottom-up Fossils Top-down MAJOR TRANSITIONS IN THE ORIGIN OF LIFE B E A LUCA MEMBRANE / METABOLISM GENOME / REPLICATION SELF-ORGANIZATION PHYSICO-CHEMICAL CONDITIONS

59 L We are here [Hug et al. (2016) Nature Microbiol.]

60 Thank you for your attention!