Origin of Life and Prokaryotes
BIOL 1407
Early Earth
• 4.6 billion years ago
(bya)
• Early atmosphere:
– No free oxygen
– Primarily nitrogen and
carbon dioxide
– High energy from
lightning, UV radiation
•
Photo Credit: Mount St. Helens, May 18, 1980, taken by
Austin Post, USGS
Conditions of Early Earth
• Intense
volcanic
activity
• Meteorite
bombardment
• Warm
environment
•
Photo Credit: Courtesy of NASA @
http://origins.jpl.nasa.gov/habitableplanets/images/ra7in16-early-earth.jpg
Earliest Evidence of Life
• Oldest fossil
organisms:
photosynthetic
cyanobacteria
• Western
Australia
• 3.5 bya
Fossil Stromatolites
• Multiple layers of
cyanobacteria
• Secreted CaCO3
 dome-shaped
structures
• First reefs
Living Stromatolites
• Shark Bay,
Australia
• Hypersaline
• Few
predators
Fossil vs. Living Cyanobacteria
Earliest Life
• Single-celled
organisms probably
evolved before 3.9
bya
• No 3.9 bya fossils
•
Photo Credit: Robert Simmon, 2008, NASA,
Wikimedia Commons
Jack Hills: Rock formation in Australia; rocks > 3.6 bya;
4.4 bya zircon crystal found in this formation
Why No 3.9 BYA Fossils?
• Few rocks date to
3.9 bya
• Tiny unicellular
fossils are hard to
find
•
Photo Credit of Proterozoic Stromatolites:
UNP, 2006, Wikimedia Commons
Molecular Fossils
• Chemical traces of
biomolecules
• 3.9 bya evidence of
prokaryotic lipids
•
Photo Credit of Hopanoid Compound: MarcoTolo,
2006, Wikimedia Commons
Abiogenesis
• Origin of life from
non-living
components
•
Photo of Stanley Miller: NASA, 1999, Wikimedia
Commons
Four Steps of Abiogenesis
• Step 1: Synthesis of
organic monomers
from inorganic
molecules
•
Photo credit for amino acid, tryptophan: Boghog2,
2007, Wikimedia Commons
Four Steps of Abiogenesis
• Step 2:
Organic
Monomers 
Organic
Polymers
• Catalysts?
•
Photo Credit for Kassinin: Edgar181,
2007, Wikimedia Commons
Four Steps of Abiogenesis
• Step 3:
Protobionts form
• Protobiont =
Organic
molecules
surrounded by
membrane-like
structure
Protobionts
• Life-like
properties:
– Reproduce
– Simple
Metabolism
– Membrane
potentials
Four Steps of Abiogenesis
• Step 4: Heredity
• Pass instructions to
offspring
• Controls protein
synthesis
• 1st genetic material:
RNA?
•
Photo Credit of Hammerhead Ribozyme: William G.
Scott, 2007, Wikimedia Commons
RNA Self-Replication
Photo Credit: Campbell, 1999
DNA replaced RNA. Why?
Picture Credit: Figure 17-3, 8th ed. Campbell, modified from original
Where did Abiogenesis Occur?
• Hypotheses:
– Hydrothermal vents
– Tide pools
– Panspermia: from
outer space
•
Photo Credit for Black Smoker: NOAA, 2006,
Wikimedia Commons
Evolution of Prokaryotes?
Photo Credit of Lassen Volcanic National Park Hot Springs:
Walter Siegmund, 2005, Wikimedia Commons
Oxygen Revolution
• Oxygen
accumulated
• Most
anaerobes died
• Some survived
in anaerobic
habitats
•
Photograph: Banded iron formations that
indicate free oxygen in oceans (2.7 bya)
Oxygen Revolution
• Oxygen 
Evolution of aerobic
respiration
• Increased ATP
production  More
energy
•
Photo Credit of Bacillus cereus on blood agar:
CDC, 2006, Wikimedia Commons
Prokaryotic Cells
• Review
– Prokaryotic
cell structure
from BIOL
1406
– Cell wall
present
Prokaryotic Cells
• Review
– Circular
chromosome
– Plasmids
Prokaryotic Cells
• Review
– Reproduction
(binary
fission)
– Membrane
transport
•
•
•
•
•
Gases
Water
Wastes
Ions
Photo: Dr. Vincent A. Fischetti, Laboratory
of Bacterial Pathogenesis and
Immunology, Rockefeller University,
Courtesy of NOAA
Prokaryotic Cell Shapes
Prokaryotic Nutrition
• Heterotrophs
• Autotrophs
Heterotrophs
• Energy from:
– Organic matter
• Chemoheterotroph
– Light
• Photoheterotroph
Autotrophs
• Energy from:
– Inorganic matter
• Chemoautotroph
– Light
• Photoautotroph
Photoautotrophs
• Photoautotrophs can be:
– Non-oxygenic
– Oxygenic
Photo: Cyanobacteria that uses oxygenic photosynthesis
Prokaryotic Domains
• Domain
Bacteria
• Domain
Archaea
Domain Bacteria
• Prokaryote
• Cell wall contains
peptidoglycan
• Circular
chromosome
– No histones
•
Photo: Beggiatoa, a sulfur bacterium.
Granules contain elemental sulfur produced
by the cell’s metabolism.
Domain Bacteria
• Five main clades of Bacteria
Clade Proteobacteria
Other Bacterial Clades
Domain Archaea
• Prokaryote
• No peptidoglycan
in cell wall
• Circular
chromosome
– Histones
•
Photo: Halobacterium, a salt-loving
(halophile) archaean. Courtesy of NASA.
Archaeans
• Most known
archaeans are
extremophiles
•
Picture Credit of Hydrothermal Vent
Archeans, Extreme Thermophiles:
Courtesy of NOAA
Halophiles
Left: Owen Lake, California
Right: Halobacterium Picture Credit: Courtesy of NASA
Extreme Thermophiles
Left: Hot Springs, Yellowstone
Right: Nevada Geyser
Methanogens
Left: Methanopyrus kandleri, 2006, PMPoon, Wikimedia Commons
Right: Methanothermobacter, Tashiror, 2006, Wikimedia Commons
Acidophiles
Left: Sulfolobus, Xiaoya Xiang,2007, Wikimedia Commons
Right: Acid mine drainage, Carol Stroker, 2005, NASA Wikimedia Commons
Archaeans in “Normal Environments”
• Oceans, soils,freshwater
Photo Credit of Worldwide View of Plankton, 1998-2004: NASA, Wikimedia Commons
Note: Archaeans are an important part of plankton. Up to 20% of world’s biomass may be archaeans.
Domain Archaea is Sister Taxon
to Domain Eukarya
Lateral Gene Transfer
• Difficult to
find
universal
ancestor
The End
Unless otherwise specified, all images in this presentation came from:
Campbell, et al. 2008. Biology, 8th ed. Pearson Benjamin Cummings.