Bacterial toxins (TOX 2)

13 important questions on Bacterial toxins (TOX 2)

What does the LPS consist of and what are the functions?

Lipopolysaccharide (LPS) contains:
  • Lipid A (toxicity)
  • Sugars (water soluble)
  • O-antigen (target for antibodies)

What are the classes of exotoxins?

  • Cytotoxins (cytolytic exotoxins)
  • A-B toxins
  • Superantigen toxins

What are mechanisms that cytotoxins use?

  • Phospholipases break down phospholipids
  • Sterol break down
  • Pore formation
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How are cytotoxins often measured?

Using blood cells (haemolysins).

What is the structure of an AB toxin?

An AB toxin consists of two subunits, A and B. The B component Binds to a host cell surface molecule, facilitating the transfer of the A subunit across the cytoplasmic membrane, where it damages the cell.

What are examples of an AB toxin? Where are they found?

  • The cholera toxin, which is found in contaminated water.
  • Shiga toxin, which is found in contaminated food.
  • Botulinum toxin, which is used as a cosmetic

What is the mechanism of a Shiga toxin?

Only the A-subunit goes into the cell, this hydrolyses the 28S RNA in the ribosomes. Then protein synthesis stops, this causes (bloody) diarrhea.

What is the mechanism of botulinum toxin?

Botulinum toxin blocks the release of the neurotransmitter acetylcholine by cleaving the SNARE proteins so that the vesicles can't bind anymore. Muscles cannot contract anymore causing paralysis.

Why is botulinum toxin used as a cosmetic?

Botulinum toxin causes paralysis which results in less wrinkles.

What is the mechanism of the tetanus toxin?

The tetanus toxin inhibits the interneuron (glycine is not released), this causes the muscle to contract constant.

What is the mechanism of the diphtheria toxin?

The A subunit catalyzes the attachment of an ADP-ribose molecule from NAD+ to EF-2. EF-2 cannot move down to the mRNA anymore and protein synthesis stops.

What are virulence enzymes?

Virulence enzymes enhance further spread of bacteria, they enhance deeper infections.

What are the symptoms of tetrodotoxin?

  • Numbness in mouth (lip, tongue) • Feeling high
  • Nausea, vomiting
  • Paralysis while being conscious

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