Brock Biology of Microorganisms 11e

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Microbial evolution
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• The evolutionary view of life
• Charles Darwin The Origin of Species
• Descent with modification
• Natural selection

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Natural Selection

• The mechanism for evolutionary adaptation of
  populations to their environments

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The finches on the Galápagos islands
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Tree of Life
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Microbial life on early earth

• Stromatolites
• Microbial mats
• Filamentous phototrophic bacteria
• Green non sulfur bacteria like

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Origin of life

• RNA life
• RNA became the simplest self-replicating entities

• Pre-requirements for self-replication
• Energy
• Heredity

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Proposed energy generating pathways in primitive
cells
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Microbial evolution and changes in earth
geochemistry
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Origin of eukaryotic cells

• Endosymbiosis
• Organells originated from the stable
  incorporation of chemoorganotrophic and
  phototrophic symbionts from the domain Bacteria

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How to examine microbial evolution

• Molecular (evolutionary) chronometers
• Universal distribution
• Homologous function
• Clocklike behavior
• Size and alignment
• Ex) Ribosomal RNAs, ATPase proteins, RecA

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Ribosomal RNAs as molecular chronometers
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Phylogenetic analysis
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The Universal Tree of Life
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How to prove microbial evolution.

• Natural selection
• Adaptive mutation
• Lateral gene transfer

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Mutation

• Spontaneous mutation
• 10-4 to 10-8 per generation
• Induced mutation
• Chemical, physical and biological agents
• Molecular basis of mutation
• Base-pair substitution
• Point mutation
• Frameshift mutation
• Deletion and insertion

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Mechanisms of genetic exchange in bacteria