L46: Bacterial evolution

• What organism was used in the bacterial evolution experiment?

  1. coli
• What does T1 phage do to E. coli?

  T1 phage kills E. coli
• What were the variations observed in resistant colonies?

  • Small variation in number of resistant colonies
  • Big variation in number of resistant colonies
• What phenotype is resistant to T1 phage?

  Ton R
• What was the conclusion of the Luria-Delbrück experiment?

  Mutations are present and selected by toxins
• How do bacteria evolve according to the Luria-Delbrück experiment?

  Bacteria evolve as a result of mutation
• What does the old data about bacterial culture resistance suggest?

  The entire culture becomes resistant with toxins
• What was the setup of Newcombe's experiment in 1949?

  • Grow for some hours
  • Re-spread (plate A)
  • Do nothing (plate B)
  • Spray with phage
  • Count colonies
• What is the expectation from Newcombe’s experiment regarding colony growth?

  More colonies on plate A (re-spread)
• What happens to single cells during growth in Newcombe's experiment?

  Single cells become colonies during growth
• What is the significance of red colonies in Newcombe's experiment?

  Only red colonies survive the phage
• What technique did Lederberg and Lederberg use in their 1952 experiment?

  • Replica plating
  • Common in microbiology and genetics
• What does the position of Ton R colonies on replica plates indicate?

  Resistance mutation happened before plating
• How does antibiotic resistance develop in bacteria?

  Antibiotic selects pre-existing mutations
• What is a key message about bacterial evolution?

  Bacteria evolve through mutation
• What are the differences between Lamarckian and Darwinian evolution?

  Lamarckian:

  • Change is directed by environment
  • Traits inherited from use

  
  

  Darwinian:

  • Change is spontaneous
  • Natural selection ensures survival
• Who outlined the theory of evolution in 1800?

  Lamarck
• What is the main idea of Darwinian evolution?

  Change is random and selected
• When was "Origin of the Species" published?

  1859
• What exceptions exist in the scientific community regarding evolution?

  • Lysenkoism: Political interference in science
  • Prokaryotes thought to be exempt from evolution
• What observation supports Lamarckian evolution in bacteria?

  Entire culture becomes resistant with toxins
• What are the hypotheses of the Luria-Delbrück experiment?

  Darwinian:

  • Random mutations appear before toxins

  
  

  Lamarckian:

  • Mutants appear only after toxins
• Who won the Nobel Prize in 1969 for work related to bacterial mutations?

  Luria and Delbrück
• What predictions are made by the Lamarckian model?

  • Mutants appear after adding T1
  • Resistance develops in response to toxins
• What predictions are made by the Darwinian model?

  • Mutants appear before adding T1
  • Resistance is pre-existing in culture