Sporulation/Stringent Response Flashcards
What sigma factors are involved in the sporulation process?
Sigma factors A, H, E, F, K, G
What is a phosphorelay?
A chain of proteins which transfer phosphate from one to the other
How is a phosphorelay similar to a 2-component system?
The phosphate is bound alternatively to histidine and aspartate on successive proteins as it passes down the chain
What are the stages of sporulation?
Transition Asymmetric division Engulfment Cortex synthesis Coat synthesis Maturation Release from mother cell
What are the principles of the strategy used to control development of an endospore?
Successive changes of gene expression, largely dependent on changing sigma factors associated with RNA polymerase. Each stage of the process involves synthesis of proteins (including sigma factors) which are required for the next stage
Secondly, communication between the developing spore and mother cell, to ensure that events in both cells are coordinated timewise
How does a phosphorelay differ from a standard 2-component system?
Phsophorelay has greater number of protein components and phospho-transfers, so there is scope for a greater number of inputs in terms of controlling the phosphorylation of the final protein (ie Spo0A).
This means the cell can responds to a greater number of influences which combine to decide on the final outcome, so it will make the ‘right choice’
What is a sigma factor?
A protein for initiating RNA synthesis
What is sporulation triggered by?
Starvation of C, N, P; desiccation; growth inhibitory temperature
In E. coli, what is the stringent response triggered by?
Rapid accumulation of ppGpp and pppGpp
What is an endospore?
A highly differentiated cell that is highly resistant to heat, chemicals, radiation
What kind of cells produce endospores?
Gram-positive bacteria especially Bacillus, Clostridium
How are spores UV resistant?
The spore’s DNA is complexed with SASPs
SASPs bind tightly to the DNA, converting it from B to more compact A form which gives protection against UV radiation, desiccation, and dry heat
How are spores heat resistant?
Largely due to dehydration
Reduced water content associated with calcium dipicolinate accumulation so cytoplasm has gel-like consistency
How are spores solvent resistant?
Due to their tough protein coats
What is the master regulator in sporulation?
Spo0A, is activated when phosphorylated
