Factors that lead to high mutation rates

  • Short generations
  • Large Populations
  • High fecundity

Experimentation Techniques

  • Microscopes and visualization has improved since the 1930’s and 1940’s
  • Utilizes the liquid handling robot and microplate reader
    •   Helps to analyze the large number of plates being run regularly

General Extinction Information

  • 99.9% of species that have existed are extinct
  • Most species become extinct within 10 million years
  • Extinction has a multitude of contributors
  • Extinction is a typical outcome
  • Causes:
    • Genetics and demographics
      • Small populations face greater risk- inbred, less fit
    • Coextinction- symbionts face greater risk
      • Symbionts are highly adapted with another species
    • Planned extinction- disease agents for eradication (smallpox, polio)
      • Is this okay?
    • Environmental change- mass extinction, habitat degradation and destruction

Viruses and Extinction

  • Viruses face environmental change
  • Viruses need to find a good cell to inhabit
  • Host biology (immunity, adaptive immunity) plays a role
  • Global changes/ecosystems affect virus stability

Options for Environmental Change

  • Adapt to environmental change
  • Wait out change
  • Let another decide fate (host)
  • Go extinct

Adapt to Environmental Change vs. Going Extinct

  • Model: Vesicular stomatitis virus (VSV)
    • ssRNA
    • arthropod born
    • easy to study- can manipulate the environment

Heterogeneous environment leads to selection for generalization

  • VSV in HeLa and Canine cells

Homogeneous environment leads to selections for specialization

  • VSV in HeLa cells only

Are generalists more advantaged?If an organism is generalized, can it withstand further change?

Both generalized and specialized in new environment

  • Generalized- higher mean, less variance—grow well
  • Specialized- lower mean, more variance

Why are generalists more advantaged?

  • Better innate immunity?
  • Better control of host apoptotic pathways?
  • Teamed with systems biologists to answer these questions.

Is specialization reversible?

  • VSV is a candidate for anti-cancer therapy
  • Which alleles cause cancer specifically?
  • How does cancer tissue prevalence affect VSV evolution?
  • Solution: Attempt to tract the fitness and molecular change in different amounts of cancer

Wait out change vs. let another decide fate

  • Model: Phage Phi 6
    • dsRNA
    • infects plants
    • same structure as influenza virus
    • Can phage evolve to withstand harsh environments?
    • Natural selection can be driven by reproduction and survival
      • Tradeoff between survival and reproduction
      • Thermotolerance worsens reproduction