Microbial Pathogenesis II

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  1. *Type III secretion systems
    • found on pathogenicity islands and associated with virulence
    • not found on non-pathogenic members of same species
    • *proteins are highly conserved
    • diversity in the secreted proteins from one strain
    • often the pathogenicity island encodes the type III apparatus, secreted proteins, chaperones and regulators
    • have intricate syringe-needle complex
    • conformational change translocates proteins
    • very fast
  2. effectors
    • type II secreted proteins
    • can be in pathogenicity island or outside but secreted via TTSS
    • typically associated with invasion and/or modulate of host function
    • typically shared regulation
    • suppress defense and promote virulence
  3. *identification of type III effectors
    • expression induced by HrpL sigma factor
    • presence of hrp-box in promoters
    • N-terminal TTSS signal peptide (ser rich, aliphatic aa in position 3 or 4, not acidic aa's in first 12 aa's)
    • delivery into hosts by TTSS
    • often have eukaryotic (host) targeting sequences
    • in order for bacterial effector to go to correct subcellular locale, must have target sequence
  4. enteropathogenic E. coli (EPEC)
    • type III secretion of its own receptor
    • host can evolve so that it is not recognized by pathogen
    • EPEC uses TTSS to deliver effector named TIR to the host cell where is then acts as receptor for intimin facilitating adhesion and pedestal formation
  5. Type IV secretion
    • uses proteins that resemble the conjugation machinery to secrete proteins and/or DNA from either the cytoplasm or periplasm
    • used to transfer bacterial DNA to host
  6. *T-DNA
    • requires T4SS for translocation of T-DNA complex into plant cell - thought
    • that the T-DNA travels through the T-Pilus, autoinducers promote T-DNA
    • transfer
    • integrated T-DNA contains genes to make a modified amino acid
Card Set
Microbial Pathogenesis II
general microbiology midterm 3
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