Toxins and secretion systems Flashcards
Why do bacteria want to harm their host?
Facilitate invasion, access nutrients, reduce competition, disseminate
What is an exotoxin?
Toxin is released into the environment–> bacteria doesn’t need to die to release it
What is an endotoxin?
Toxinis part of the bacterial membrane–> bacteria needs to die to release it
Examples of mechanisms of toxin action?
Making pores in the targets membrane, inhibition of protein synthesis, activating secondary messenger pathways
Example of pore making toxin?
Shiga toxin
ROles of toxins in pathogenicity?
Immune system manipulation, promotion of inflammation, biofilm formation enhancement
From which type of bacteria is lipopolysaccharide produced?
Gram -ve
How can lipopolysaccharide result in an excessive or uncontrolled immune response?
When a bacteria is engulfed, it lyses and releases LPS from its cell wall
LPS binds to toll-like receptor 4 of immune cells
immune cells cause cytokine release–> inflammation
more LPS = more inflammation
Example of an exotoxin?
Cholera toxin
Cholera toxin structure?
Made up of an A and B subunit
Role of A subunit in cholera toxin?
Catalytic subunit
Role of B subunit in cholera toxin?
Binding subunit–> binds to ganglia site in the membrane of the cell
What happens once the B subunit of the cholera toxin has bound to the GM1 ganglioside?
It opens the channel and allows the A subunit to enter the cell
What does the A subunit of the cholera toxin do once inside the cell?
Binds with the G proteins and activates them
WHat do the G proteins do following binding of the A subunit and activation?
Bind with adenylate cyclase, which produces cAMP
What does cAMP do following production of it by adenylate cyclase?
Phosphorylates CFTR, which allow the CFTR channels to open
What happens once the CFTR channels are open?
Lots of Cl- leaves the cell, and water as well due to the osmotic force–> diarrhoea
What is a pyrogenic infection?
A pyogenic infection is an infection that leads to the production of pus, a thick fluid composed of white blood cells, dead tissue, and bacteria
First part of a pyrogenic infection?
Microbe is engulfed by a macrophage–> protein is broken down
What happens as a result of protein breakdown in a pyrogenic infection?
LPS is released and causes the release of cytokines
What happens as a result of cytokine release caused by LPS release?
Cytokines cause the pituitary gland to secrete prostaglandins, which causes fever
Why can treating a pyrogenic infection with antibiotics worsen it?
Kill more bacteria so more LPS produced and an even higher immune response
Possible symptoms of overactivation of the pituitary gland?
Altered blood coagulation, internal bleeding, vasodilation, shock, death
LPS toxicity?
V low–> need a v high conc to have the worst effects
