Dissecting virulence of E. coli O157: H7 using genome alignments Escherichia coli is a normal resident of the mammalian gut



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Dissecting virulence of E. coli O157:H7 using genome alignments


Escherichia coli is a normal resident of the mammalian gut

  • Escherichia coli is a normal resident of the mammalian gut

    • Most strains are non-pathogenic
    • E. coli K12 – lab strain
    • Some strains are pathogenic to human: E. coli O157:H7
    • Cause diarrhea, cramps
    • The most virulent strains of O157:H7 can result in death
  • Disease symptoms caused in part by the bacterial production of Shiga toxin

    • Shiga toxins act to inhibit protein synthesis in the host
    • Cytotoxic
  • Pathogenic strains transmitted through consumption of contaminated foods, (undercooked ground meat products/vegetables watered with contaminated water)



Microbes living in or on a host AND

  • Microbes living in or on a host AND

  • Producing negative consequences to host

    • Killing host cells
    • Inducing an immune response in host (toxic shock)
    • Reducing the “fitness” of the host
  • Virulence factors are proteins that facilitate the microbes ability to exploit the host



Virulence = severity of damage to the host

  • Virulence = severity of damage to the host

  • Why would a pathogen “want” to harm the host?

    • Virulence is sometime a byproduct of the bacterial efforts to live and propagate in a host


Pathogenic bacteria and virulence factors



14 categories of virulence factors for E. coli O157:H7





Differ in degree of virulence

  • Differ in degree of virulence

  • Most virulence factors are not yet known

  • How can we begin to make hypotheses about which genes play roles in the virulence of different strains?











Comparison of the genome structire of pathogenic vs. non-pathogenic strains indicate that pathogenesis is associated with multi-gene “islands”

  • Comparison of the genome structire of pathogenic vs. non-pathogenic strains indicate that pathogenesis is associated with multi-gene “islands”

  • The functions of some of the genes could be inferred using BLAST







Background information regarding epidemiology of E. coli O157:H7 outbreaks





As of 2010, there are 15 E. coli O157:H7 genomes sequenced. We will have you focus on three that are all in the ASAP database (http://asap.ahabs.wisc.edu/asap/home.php)



Comparative genomics using the tool Mauve: Multiple Genome Aligner



Student individual projects



Here is a list of a few virulence factors




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