Lecture 3 Flashcards
What is commonly the limiting factor for bacterial growth in humans?
Oxygen
What effect does bacterial numbers have on oxygen availability?
As the numbers increase diffusion is unable to supply sufficient oxygen to support metabolism of carbon substrates to Carbon dioxide
What three things are bacteria communicating with?
The host, other bacteria and the environment
Why does fermentation happen?
A lack of oxygen means there is no electron acceptor and the NADH but be recycled
What advantage does respiration have over fermentation?
More ATP production
What type of forces drives ATP production in oxygen respiration?
How is this force generated?
The proton motive force through ATP synthase
Reduction of NADH and FADH2, moves protons into the intermembrane space of mitochondria. The electrons are then collected by oxygen. The protons move through ATP synthase and are used to make water with the reduced oxygen.
What components of the electron transport chain is E.coli missing?
bc1 complex and cytochrome C
Still has NADH dehydrogenase, quinol and oxidase
Why can E.coli respire when oxygen is not available?
It has a range of different pathways it can use to dispose of the electrons from respiration. They will use the pathway which is most energetically favourable. However, it will always use oxygen preferentially.
What happens if electrons leak from the respiratory chain?
Why is this dangerous for the cell?
They catalyse oxygens partial reduction to superoxide. Superoxide will react with itself to form peroxide.
Both of these are able to cause dmage to the cell and are considered highly toxic; e.g. oxidating nucleic acids and cause DNA damage
How can enteric bacteria respond to the formation of the oxidative stress molecules?
They have superoxide dismutases which will break superoxide into oxygen and peroxidases to catalyse it to hydroxyl groups and then to water.
What types of cells form oxygen radicals deliberately?
How?
Why?
Macrophages and competing bacteria
NADPH oxidase and pyruvate oxidase
In an attempt to kill infectious agents or competition
Outline how E.coli deals with nutrient starvation due to lack of oxygen
E.coli will use FNR (fumerate and nitrate reductase regulator). Which exists as a monomeric protein in aerobic conditions but will dimerise when under anaerobic conditions. The dimeric FNR can then activate expression of genes required under anaerobic conditions.
Which two things were shown to be important for shigella virulence?
T3SS and FNR
What is the role of the T3SS?
Secrtes Ipa proteins into the host to mediate cell invasion
What effect was oxygen shown to have?
When anaerobic conditions were used more Shigella survived
