Origin of Life
Kai Finster
Department of Bioscience
Stellar Astrophysics Center
Quotes:
• “The undreamt –of breakthrough of molecular biology has made the problem of the origin of life a greater riddle than it was before: we have acquired new and deeper problems” K.R. Popper, 1974
• “Nobody understands the origin of life. If they say they do, they are probably trying to fool you”. K. Nealson, 2002
• “To go from a bacterium to people is less of a step than to go from a mixture of amino acids to a bacterium”. L. Margulis
The basic enigma
Goal
• Explain the appearance of the minimum unit of life – which is the cell
Overview
– Definitions of Life
– Spontaneous generation
• Pasteurs swan‐bottle neck experiments
– Oparin – Haldane concept – heterotrophic origin
• Miller experiment
• Organics in space ‐ seeding from meteorites
– Information or Metabolism first – some examples?
• RNA world • Wächtershäusers pyrite derived Life
• Russells ironsulfide proto‐cells
– Lifes imprints • Great oxygenation event and its consequences for evolution
What is Life?
• Participants definitions:
What is Life?
• “a living organism is an organized unit, which can carry out metabolic reactions, defend itself against injury, respond to stimuli, and has the capacity to be at least a partner in reproduction.” Koshland , Science 2002.
• “Life is a self‐sustained chemical system capable of undergoing Darwinian evolution” Joyce, 1994
What is Life?
• The seven pillars of Life (Koshland, 2002):
– Program: organized plan describing both the ingredients and the kinetics of their interactions (DNA)
– Improvisation: to response to changing conditions (mutations + selection) – Compartimentalization: confined to a limited volume (cells), surrounded by a surface (membrane); maintain the concentration and the arrangement of the interior = protection from the outside.
What is Life?
• The seven pillars of Life (Koshland, 2002):
– Energy: open and metabolizing system; recycling of chemicals in cells; neg‐entropy; solar energy.
– Regeneration: compensation for thermodynamic loss by passive or active transport of matter into and out of the cell; constant synthesis of constituents; reproduction.
– Adaptability: behavioral response that is part of the program, response to detrimental factors like hunger and heat.
– Seclusion: isolation of pathway – no accidental crossing over allows parallel handling in a tiny volume Spontaneous generation
Spontaneous generation
Time line of the living
Organics on Earth and from Space
Miller‐Urey experiment
Miller‐Urey experiment‐outcome
Murchinson –meteorite
organics from space
Murchinson –meteorite
organics from space
Complex aromatic compounds:
Organics from space
Prebiotic processes in solution
Haldane – Oparin concept of Primordial soup
Prebiotic processes
• Haldane – Oparin concept – Primordial soup
– Coacervates: tiny spherical droplet of assorted organic molecules (specifically, lipid molecules) which is held together by hydrophobic forces from a surrounding liquid.
Prebiotic processes
Prebiotic processes Annual Reviews
Prebiotic processes
Prebiotic processes
The RNA world
The RNA world
Prebiotic processes in solution
Prebiotic processes on surfaces
The Role of Clays
Wächtershäusers concept of the origin of Life
Wächtershäusers concept of the origin of Life
Russells concept of the origin of Life
Russells concept of the origin of Life
Annual Reviews
Types of metabolic processes in modern
vent system:
Tree of Life
Major “invention” ‐ photosynthesis
Imprints of Life
• The great oxidation event
Relationships between geologic time, atmospheric oxygen concentration, and the
phylogenetic history of early life forms, animals, and plants.
Flück M et al. Integr. Comp. Biol. 2007;47:524-531
© The Author 2007. Published by Oxford University Press on behalf of the Society for Integrative
and Comparative Biology. All rights reserved. For permissions please email:
[email protected].
Imprints of Life
Imprints of Life
Summary
• The transition from organic chemistry is still unresolved
• The evolution of the genetic code is not understood – RNA world may be an answer
• The evolution of metabolic pathway is not understood – Iron sulfur chemistry may play an important role
• Atmospheric signatures may be a key to life detection on other planets.