Sigma factors in sporulation

Question 1

describe Sporulation by Bacillus subtilis

Answer 1

1. Adaptation to starvation Produce resistant spore and program mother cell death
2. two cells with identical genomes initiate different programmes of gene expression
   – germ line and terminally differentiated cells

Question 2

how do nutrient conditions change sporulation?

Answer 2

1. Nutrient replete conditions: double in size and divide into two identical cells- vegetative cell growth
2. Nutrient limited conditions: developmental switch leading asymmetric division, death of one cell and production of tough dormant endospore

Question 3

What are the signals for sporulation?

Answer 3

1. Nutrient availability
2. Population density
3. Stage of cell division

Question 4

describe SpoOA phosphorelay system

Answer 4

1. SpoOA initiates sporulation
2. from sigmaA and sigmaH promoter
3. SpoOA-P controls genes sigma F prespore and sigma E - mother cell.

Question 5

what does SpoOA-P activate?

Answer 5

• expression of sigmaF and sigmaE

– responsible for first level of spore specific and mother cell specific gene expression

Question 6

How is sigmaF activated in spore only?

Answer 6

1. Localisation of SpoIIE septum of the prespore.
2. dephospho rylation of AA Binds AB
3. Free sigma F

Question 7

why is it important to Co-ordination of sigma cascades e.g. activation sigmaE?

Answer 7

1. functional spore requires mother cell input

2. if spore not finish programme but mother starts then both cells die

Question 8

Sigma E activation

Answer 8

1. Activation of sigma F leads to
   transcription of spoIIR gene in prespore
2. SpoIIR must enter mother cell.
3. SpoIIR protein activates SpoIIGA protease
4. protease chops off part of pro-sigmaE to leave active sigmaE

Question 9

mother spores job?

Answer 9

1. contains sigmaE directs transcription of sigmaK.

2. sigmaK transcription factor for genes sealing spore important not expressed too early

Question 10

describe SigmaK activation

Answer 10

1. depends on sigma G signalling protein from spore
2. two inhibitor proteins surround protease in membrane
3. once signal received inhibition stopped and pro-sigma K cleaved to active form.