L17- Exotoxins and endotoxins

Question 1

What is it that causes symptoms?

Answer 1

Toxins

Question 2

What did Roux and Yersin do in 1888?

Answer 2

Used cell free extracts of corynebacterium diptheria.
First realisation that bacteria secreted something that caused disease.
Discovered that injection of toxin into animal raised antibodies.
“primitive” form of vaccine.

Question 3

What are some properties of toxins?

Answer 3

• Soluble simple proteins
• Many are enzymes
• Many are coded by bacteriophages and plasmid genes

Question 4

What are the 3 types of exotoxin?

Answer 4

1. Enterotoxin- targets the GIT
2. Cytotoxin- damages individual cells
3. Neurotoxin- interferes with nerve impulses

Question 5

What do enterotoxins do>

Answer 5

Stimulate GIT cells abnormally. Cause loads of fluid secretion-> diarrhoea

Question 6

Guve 3 examples of eneterotoxins?

Answer 6

1. Cholera toxin- vibrio cholarae
2. E. coli
3. Shiga toxin (shigella dysenteriae)

Question 7

What do cytotoxins do?

Answer 7

Kill cells by enzymatic attack

Question 8

What do membrane disrupting cytotoxins do?

Answer 8

• Bind to cholesterol in the host membranes
• Forms pores in the membrane
• Contents released, kills cells
  e. g. streptolysin O releases haemoglobin

Question 9

Describe Beta haemolysis by E coli?

Answer 9

E. Coli cytotoxin on an agar plate- haemolysin forms pores by lysing red blood cells. It has a mushroom structure.

Question 10

What do phospholipase enzymes (cytotoxins) do?

Answer 10

Removed charged head group from lipid of phospholipids in host cell membrane.
Destabilizes membrane and cell dies.

Question 11

What’s an example of phospholipase enzymes?

Answer 11

• Clostridium perfingens- cause gase gangrene.
• Produces 12 exotoxins
• Major toxin is a phospholipase, lyses cells

Question 12

What do neurotoxins do?

Answer 12

Interfere with normal transmission of nerve impulses

Question 13

What’s an example of a neurotoxin?

Answer 13

• Botulinum toxin

- Most potent poison known. Prevents transmission to muscles, so they can;t contract.

Question 14

What can neurotoxins like Botulinum toxin be used for?

Answer 14

Botox! Relaxes muscles in overactive muscle and reduces wrinkles.

Question 15

What are the parts of enterotoxins?

Answer 15

A-B structure.
A subunit- enzymatically active inside the cell.
can’t bind

B subunit- (5 subunits)- Attaches on to receptor
gets A inside
Biologically inactive

Question 16

Which endotoxin is part of the lipopolysaccharide in gram negative bacteria?

Answer 16

LIPID A.