Stationary Phase

Question 1

Stationary phase

Answer 1

Generalised stress response to starvation, toxicity etc.
bacteria spend most of their time in this state
cell wall thicker
growth enzymes redirected
RPoS at the centre of all this
not random - senses environmental conditions

Question 2

RpoS

Answer 2

Master regulator of stationary phase
sigma^2 subunit of RNAP
transcribed in late exponential phase

Question 3

GASP phenotype

Answer 3

Growth Advantage in Stationary Phase phenotype
the ability of cells aged in long-term batch cultures to out-compete cells from younger cultures.
Mutants of RpoS, LRP and amino acid transporters
increased adaptability compared to younger bacteria

Question 4

Ribosome modulation factor

Answer 4

Ribosome associated protein that is produced during stringent response
Helps prevent ribosome degradation + induce resting stateThe expression of ribosome modulation factor is regulated by (p)ppGpp (which is induced by amino acid starvation), cAMP-CRP (which is stimulated by reduced metabolic energy), and transcription factors involved in biofilm formation

Question 5

Sucrose density centrifugation

Answer 5

Used to investigate DNA/RNA macromolecules
a sample containing a mixture of different size macromolecules is layered on the surface of a gradient whose density increases linearly from top to bottom

Question 6

RaiA

Answer 6

Ribosome associated inhibitor A
associates with RMF to induce ribosome hibernation

Question 7

HPF

Answer 7

Hibernation promoting factor
Binds ribosome dimers together to form 100S ribosome dimer complex

Question 8

LRP

Answer 8

Leucine response protein
a global regulator of the genes for transport, biosynthesis and catabolism of amino acids to establish their balance needed for protein synthesis.

Question 9

IRA protein

Answer 9

Deactivates RsrB which then can’t activate ClpXP protease that degrades RpoS

Question 10

RpoS transcription regulation

Answer 10

Regulated by CRP with one activator site and one inhibitor site.
CRP protein binds cAMP, which causes a conformational change that allows CRP to bind tightly to a specific DNA site in the promoters of the genes it controls. CRP then activates transcription through direct protein–protein interactions with RNA polymerase.

Question 11

CRP

Answer 11

cAMP receptor protein

Question 12

RpoS translation regulation

Answer 12

controlled by small non-coding RNAs e.g.
DsrA –> thermocontrol, opens mRNA hairpin of RpoS
RprA –> cell surface stress signalled by RcsC sensor kinase
OxyS –> oxidative shock, regulated by OxyR by mechanism unknown, hfq involved
activates KatG (catalase for oxidative stress)

Question 13

What does it mean that long-term stationary phase cultures are dynamic?

Answer 13

Constant population size
Cycles of life and death - competitive waves take over and die

Question 14

SPANC model

Answer 14

Self-Preservation And Nutritional Competence

Porin-mediated outer membrane permeability and the RpoS-controlled general stress response both involve a trade-off between self-preservation and nutritional competence