Stress in Pro and Eukaryotes Flashcards
What things cause stress in a microorganism?
Metals, temperature, pH, osmolytes and pro-oxidants.
What is an adaptive response to stress?
When you put a microorganism under some stress, then you put it under high stress, it survives.
What is cross tolerance?
When you put a microorganism under one type of stress (stress A) then you put in under a previously lethal stress (stress B) it can survive.
What is different in the responses of microorganisms to rapid onset of stress compared to slow onset of stress?
Rapid onset of stress- General and stress specific responses are activated.
Slow onset of stress- Only stress specific responses are activated.
What are the 2 proteins that are involved in the stress response?
1- Sensor proteins (found on membranes) (eg. kinases)
2- Response regulator proteins (normally a DNA binding protein that regulated transcription). - when it is phosphorylated it acts as a repressor.
What is the difference between cold stress and heat stress?
Cold stress - membrane is less fluid, less protein catalytic activity, cell makes cytoprotectants (eg. Trehalose) which activates desaturase enzymes (unsaturated fatty acids have a kink), heat shock proteins are synthesised.
Heat stress- hydrogen bonds are disrupted, DNA is affected, membrane is too fluid, proteins are denatured, it synthesises heat shock proteins (eg. Chaperones) and cytoprotectants (eg. Trehalose).
What are the 2 principle heat-shock regulons in E.coli?
Major regulon: sigma-32 regulon (30 genes)… it’s mRNA and proteins are stabilised at high temp, hence heat shock response)
Minor regulon: sigma-E regulon (3 genes)
What are the 2 types of osmotic stress?
Hyper osmotic stress (water leaves cell and cell shrinks)
Hypo osmotic stress (water enters cell)
What is a cells response to osmotic stress?
Solutes are either broken down or made to counteract the effects of osmotic stress.
The cell synthesises the cytoprotectant, Trehalose.
In hypo osmotic stress the cell membrane expands and so this can trigger the synthesis of more cell wall.
What does a microorganism do in oxidative stress?
It produces Reactive Oxygen Species (ROS) which is damaging to itself.
To make itself better it makes more ROS-scavengers eg. Catalase and makes enzymes which repair oxidative damage.
