Origins and Early Evolution of Life Richard Vann CBI 206/ANESTH 445 Physiology and Medicine of...
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Transcript of Origins and Early Evolution of Life Richard Vann CBI 206/ANESTH 445 Physiology and Medicine of...
Origins and Early Evolutionof Life
Richard VannCBI 206/ANESTH 445
Physiology and Medicine of Extreme EnvironmentsSpring 2013
1
Origin of Life Topics• Who, when, what, where, how, why• Discussion
2
Panspermia & Spontaneous Generation
•Panspermia: life exists throughout the universe•Spontaneous generation: life forms by the action of the sun on the primordial terrestrial slime
Aristotle384-322 BC
Anaximander611-547 BC
Anaxagoras500?-428 BC
3
Recipe for Mice:Jan Baptista van Helmont (1580-1644)
• Put a soiled shirt and grains of wheat in a jar and let them ferment
• Mice form after 21 days• No experimental evidence
provided
4
Friedrich Wöhler & Urea (1828)
• Wöhler made urea by heating ammonium cyanate
• "I can no longer, so to speak, hold my chemical water and must tell you that I can make urea without needing a kidney, whether of man or dog."
• A founder of organic chemistry5
• Organic and non-living compounds are different (“élan vital, life force, will-to-live”)
Death of Spontaneous Generation:Louis Pasteur (1859)
• Living systems arise biotically from other living systems
6
Charles Darwin (1871)
“But if (& oh what a big if) we could conceive in some warm little pond with all sorts of ammonia & phosphoric salts, - light, heat, electricity, etc. present, that a protein compound was chemically formed, ready to undergo still more complex changes …”
- letter to Joseph Hooker7
Aleksandr Oparin (1924)
•Early atmosphere was strongly reducing
•CH4, NH3, H2O , H2 (no O2)•Sunlight reacted with non-living chemicals in the “primeval soup”•Unique, abiogenic, spontaneous generation of life•No difference between a living organism and lifeless matter
8
J.B.S. Haldane (1929)
“When ultra-violet light acts on a mixture of water, carbon dioxide and ammonia, a vast variety of organic substances are made, including sugars and apparently some of the materials from which proteins are built up … [B]efore the origin of life they must have accumulated till the primitive oceans reached the consistency of hot dilute soup.”
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Harold Urey1893-1981
Stanley Miller1930-2007
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Miller-Urey Ocean-Atmosphere (1953)
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Miller (1953). Production of amino acids under possible primitive Earth conditions. Science 117: 528.
12
Space• Radio astronomy found evidence of organic
molecules on space dust• Laboratory simulations of deep space created
organic molecules
13
• Collisions of comets with primitive Earth• Murchison meteorite in Australia 1969
contained organic molecules
Exogenesis and Mars
• Mars may have been habitable a billion years before Earth
• A meteorite from Mars recovered in 1984 was claimed to contain fossil life but this is disputed
• The question of exogenesis from Mars to Earth is unresolved
14
Hydrothermal Volcanic Vents
Hydrothermal vents
DSV Alvin (1977)
15
Giant Clams
Tube Worms
Corliss, Baross & Hoffman. 1981. An hypothesis concerning the relationship between submarine hot springs and the origin of life on Earth. Oceanolgica Acta 4 (Suppl): 59-69.
16
Deep, Hot Biosphere
Laboratory Simulations• Reactants: N2, CO2, S, Fe• Minerals: Fe-S, Ni-S• Products: NH3, amino acids,
peptide bonds, C-fixation Fe-complexes
Rock-Eating Bacteria
Thermophiles
Yellowstone (1966)
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Origin of Primordial Molecules- Deamer (2002)
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Timeline~13.7 bya “Big Bang” (atomic evolution)~11.5 Supernovae & heavy elements ~4.6 Sun, solar system & Earth~4.4 Oceans formed~4.4-3.9 Chemical evolution~4.2-4.0 Earliest life at hydrothermal vents?4.0-3.7 Earliest life at sea level?~3.5 Earliest fossils (Apex chert, WestAus)~0.5 Organic evolution (‘naked genes’)~1 mya Social evolution (humans) 19
When was Earth Ready for Life?- Schopf (2002)
Oldest Fossils:Stromatolites
Origin ofSustained Life
Sterilizing Meteor Storms
Successof Life
4.5 4.0 3.9 3.03.5
Billions of Years Ago (bya)20
PlanetaryBirth
Life and the Atmosphere
STERILIZINGMETEOR STORMS
OLDEST FOSSILS:STROMATOLITES
SUSTAINEDLIFE
EUKARYOTESCHEMICALEVOLUTION
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BIF
OXYGENCATASTROPHE
O2 metab
3.9 – 3.5 bya
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Manyearlylife
forms(temperature,
anaerobic,radiation,arsenic,
salt)
OO22 Catastrophe Catastrophe LUCALUCA
PresentBiochemistry
(ATP, Krebs cycle,RNA, DNA)
Time
NASA Definition of Life• “A self-sustaining chemical system
capable of Darwinian evolution”–Self-sustaining (energy production)–Chemical system (cell membranes)–Darwinian evolution (replication)
• What’s the driving force that makes this system run?
23
Energy and Complexity- Chaisson (2001)
Stars 2 erg/g/secPlanets 75Large animals 20,000Human brain 74,000Society 500,000
24
Sagaminopteron Ornatum
25
Thermodynamics• 1st Law: energy is conserved, not created or
destroyed– all forms of energy are inter-convertible
• 2nd Law: heat flows from higher to lower temp– Energy conversions are never complete
• Some energy is always lost to the environment as wasted heat (ΔQ)
– Entropy (S) = wasted heat divided by the environmental temperature (ΔS=ΔQ/T)
• Entropy is generated with each energy conversion • The entropy of a closed system always increases• Entropy is “time’s arrow”Entropy is “time’s arrow” 26
Entropy Generation Rate- Silva (2008)
27
Entropy (S) and “Heat-Death”
Universe
Life
dS/dt > 0∆Suniverse > 0
Energy
28
∆Slife = 0
• Life is maintained by energy input from the universe & entropy export to the universe
• Does time stop when dS/dt=0?
How Did Early Life Get Energy?
• Heterotroph – the ‘premordial soup’ provided high energy complex molecules that had been abiotically synthesized (Oparin & Haldane). – Modern heterotrophs eat other organisms.
• Autotroph – energy derived from oxidation of ammonia to nitrous & nitric acid, sulfur to sulfurate, iron to iron oxide, and methane to carbon dioxide & hydrogen.
29
Reverse TCA Cycle
30
2 CO2 + 4 H2 2 H2O + C2O2 (acetate)no catalyst:very slow
Iron-Sulfur World - Günter Wächtershäuser
• Life originated on mineral surfaces near deep hydrothermal vents (“primordial sandwich”)
• 1st cells were lipid bubbles on mineral surfaces
• Metabolism predated genetics with iron sulfides as energy source (chemoautotrophs)
• Photoautotrophs evolved as chemical energy was deleted
• Autocatalytic & self-replicating metabolism
31
Thioester World- de Duve
• Thioester bonds are high energy & played the role of ATP in early life
• Thioesters are intermediates in the ancient processes leading to ATP
• Thioesters evolved into ATP
32
Driving Force: Entropy & Probability
• Most probable configuration has greatest entropy
33
Less probable (S1) More probable (S2)
S3 < S4
Less probable (S3) More probable (S4)
• Attractive & repulsive intermolecular forces determine the most probable configuration
S1 < S2
• Heat is molecular motion
Simulation of Self-Assemblyhttp://complex.upf.es/~harold/lipid_world/index.html
34
Before self-assembly (low S) After self-assembly (high S)
Self-Assembly of Liposomes- Bangham (1961); Deamer (1997, 2002)
35
MurchinsonMeteoriteextract
MurchinsonLiposomes
Biological Self-Assembly• Lipid bi-layer membranes
36Antibody & antigen Substrate & enzyme
• Structure guided by attractive & repulsive forces (“lock-and-key”)
Lipid World - Serge, Ben-Eli, Deamer, Lancet (2000)
• Coacervates. 1-100 μ “proto-cells” (Oparin 1932)
• Microspheres formed by heat-polymerized amino acids (Fox 1957)
• Murchison carbonaceous meteorite (Deamer 1997). Catalytic activity, replication, etc. also proposed.
37
Tobacco Mosaic Virus (TMV)• TMV self-assembly from separated protein & RNA
38
Darwinian Evolution- Darwin (1959)
• Modified progeny of ‘A’ are better adapted to the environment & survive
• Subsequent generations of ‘B’ – ‘F’ are unmodified & become extinct
• Track ‘A’s genealogy into deep time to find LUCA
• Fossil record too limited
39
Systematics or Phylogenetics- Haeckel (1866)
• Commonality of traits– Animals – consumers– Plants – producers– Protists – reducers
• Eucaryote* – nucleus, etc.• Prokaryote* – no nucleus
* Stanier (1961) [common biochemistry]
• LUCA
• Fossils–no! Genetic code?40
Evolutionarytime
DNA Code
Cytosine
Adenine
Guanine
Thymine41
RNA World
• RNA-based life predated DNA life• RNA can act as its own catalyst (‘ribozyme’) so
proteins were unnecessary• RNA evolved into DNA which is more stable• Ribosomal RNA (rRNA) is a remnant of the
RNA World• Problems: RNA chemically fragile, difficult to
synthesize abiotically, limited catalysis
42
Pre-RNA Worlds• Alternative nucleic acids
– RNA precursors: threose nucleic acid (TNA), PNA (peptose), GNA (glycol)
43
• PAH (Polycyclic Aromatic Hydrocarbon) World– PAHs are amphiphilic and might
self-organize in stacks as a nucleic acid backbone
Clay World - Cairns-Smith (1985)
• Proto-life was inorganic and existed on solid surfaces such as clays
• Clays catalyzed formation of complex organic molecules
• Clays acted as template for RNA self-assembly and evolved into RNA
• Natural selection enhanced their replication potential
44
Ribosome- Woese (1981)
• Site of protein synthesis in all cells– Functionally constant over time
• Ribosomal RNA 16S– RNA “dictionaries” → phylogenetic trees– Genotype → phenotype (cell membranes)
45
‘progenotes’ 46
Phylogenetic Tree of Life (16S rRNA)- Woese (1990)
Horizontal Gene Transfer (HGT)
• ‘Infective heredity’• Endosymbiosis
– Mitochondria (1.7-2 bya)– Plastids (1.5 bya)
• Antibiotic resistance– Plasmids
• Viruses
47
Artificial HGT (Social Evolution)- Craig Venter
48
• Sequence yeast cell genome (Myoplasma mycoides)
• Synthesize M. mycoides genome from lab chemicals
• Transplant synthetic genome into recipient cell (M. capricolum)
• Test viability of synthetic cell• Next find minimal viable synthetic genome• Applications – bio-fuels, vaccines, drugs, etc.
• What are the limitations of the field?• What came first: metabolism or replication?• What would be the result if you could re-run
evolution again beginning from the Big Bang?• What would be the result if you re-ran
evolution from the Big Bang 1,000 times?• Is laboratory investigation of the creation of
some form of life valuable? • If you were in charge of an origin of life lab,
where might you focus your efforts?
49