sporulation

Question 1

what is a diaspore

Answer 1

a type of spore found in some bacteria as well as plans and fungi. it has a dispersal mechanism after sexual reproduction

Question 2

what is an endospore

Answer 2

a type of spore in bacteria which is metabolically inert and is designed to survive harsh conditions and periods of starvation

Question 3

why is sporulation a last resort

Answer 3

is it energetically costly, takes a long time and is irreversible. it only occurs if stationary phase is not enough to enable survival

Question 4

what is the transition phase

Answer 4

bacteria has entered stationary phase but has not yet committed to sporulation

Question 5

which three transcription factors are responsible for controlling sporulation

Answer 5

AbrB, CodY and SpoOA.

Question 6

what is the role of AbrB

Answer 6

it represses stationary phase genes during exponential phase

Question 7

what does CodY do

Answer 7

it represses early- stationary and sporulation genes. it is only active when bound by GTP so is indicative of nutrient levels

Question 8

what does SpoOA do

Answer 8

it is the master regulator or sporulation. at low SpoOAP (monomer) it represses transcription but at high SpoOAP (dimer) it activates transcription of sporulation genes. it regulates 121 genes

Question 9

how is SpoOA phosphorylated

Answer 9

by a relay of Pi via 5 sensor kinases (Kin A-E), SpoOF, SpoOB, then the D region of SpoOA. the steps allow greater levels of control and sporolation will only occur when there is a threshold amount of SpoOAP dimer present

Question 10

what upregulates and downregulates phosphorylation of SpoOA

Answer 10

it is upregulated by KipA and downregulated by sda

Question 11

what unregulated and downregulates transcription of SpoOA

Answer 11

it is promoted by sigma H and is repressed by CodY

Question 12

what is the role of RAP phosphatase

Answer 12

it removes Pi from SpoOF-P, preventing the formation of SpoOA-P. this is done at a high concentration of bacterial cells which is detected by the movement of small peptides in and out of cells

Question 13

what is the role of SpoOE

Answer 13

it encodes a phosphatase which dephosphorylates SpoOA-P. this is done at a low, constant rate to prevent accidental build up and premature sporulation

Question 14

how does the FtsZ ring cause cell division in normal vegetative division

Answer 14

it is positioned in the centre of the cell by proteins DivIVA and MincD. it forms a septum to split the cell into two discrete cells

Question 15

how does the FtsZ ring cause asymmetrical cell division

Answer 15

more FtsZ is produced so it coils. this coil splits and forms two rings- one at each pole. one of these forms a septum to divide the cell, assisted by SpoIIE phosphatase

Question 16

what is the role of sda in asymmetrical cell division

Answer 16

it senses whether DNA replication is incomplete. if so, it inhibits phosphorypation of KinA and therefore prevents sporulation

Question 17

what is the role of SirA in asymmetrical cell division

Answer 17

is displaces DNAA from the OriC (if located there it will initiate replication). this prevents replication being initiated again within the prespore

Question 18

what promotes transcription of SirA

Answer 18

SpoOA-P

Question 19

how do chromosomes enter the presopore

Answer 19

they are stretched into a filament due to attraction of SopOJ (bound close to OriC) to DivIVA (located at the poles). only 1/3 is trapped in the prespore at the initial division

Question 20

how is the whole chromosome moved into the prespore

Answer 20

DNA translocase SpoIIE forms a two channel pore. the two arms of the chromosome are pumped in simultaneously

Question 21

which sigma factors are active at asymmetrical division

Answer 21

sigma E in the mother and sigma F in the prespore

Question 22

which sigma factors are active at engulfment

Answer 22

sigma K in the mother and sigma G in the prespore

Question 23

how sis activation of sigma F controlled

Answer 23

it is inactive when bound by anti sigma factor SpoIIAB. it is active when bound by anti anti sigma factor SpoIIAA

Question 24

when is SpoIIAA active and inactive

Answer 24

it is inactivated when phosporylated by SpoIIAB (also a kinase). it is active when dephosphorylated by SpoIIE (located in the Z ring)

Question 25

why is SpoIIAA only active in the prespore, not the mother

Answer 25

there is the same exposure to the Z ring but a much smaller volume. the SA to volume ratio is greater

Question 26

why can’t SpoIIAA and SpoIIAB both bind to sigma F

Answer 26

steric displacement. they bind to the same region so the binding or one will displace the other

Question 27

how is sigma E synthesised and activated

Answer 27

it is synthesis as pro sigma E. the inhibiting protein domain is cleaved by GA protease once it has located in the septum and been activated by the binding of SppoIIR on the presopre side

Question 28

how is sigma G synthesised and activated

Answer 28

it is synthesised inactive due to being bound by SpoIIAB. this is cleaved by SpoIIIJ (produced in the mother) which localises in the septum, cleaved SpoIIAB and activates sigma G

Question 29

how is sigma K synthesised and activated

Answer 29

to be synthesised the Skin region which divides the gene has to be removed by a SpoIVCA site specific recombinase to produce pro sigma K. this is activated by SpoIVB protease (mediated by sigma G in prespore) cleaving SpoIVFA and BofA protein off pro sigma K, activating it

Question 30

how is the prespore dehydrated

Answer 30

low weight proteins eg dipicolonic acid enter the prespore along with Ca2+ which causes water to move out of the cell