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L4 Molecular Microbiology > Week 3: Regulation of bacterial gene expression by small molecule signalling - Cyclic di-GMP > Flashcards

Week 3: Regulation of bacterial gene expression by small molecule signalling - Cyclic di-GMP Flashcards

1
Q

What bacteria use c-di-GMP?

A

NEARLY ALL BACTERIA

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2
Q

How is c-di-GMO generated?

A

is generated from GTP by diguanylate cyclases (DGCs)

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3
Q

How is c-di-GMP broken down?

A

broken down by two classes of c-di-GMP-specific phosphodiesterases (PDEs), EAL-domain or HD-GYP domain

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4
Q

What signals effect the level of DGC and PDEs?

A

internal and extrinsic signals

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5
Q

What are DGCs?

A

diguanylate cyclases

promote GTP–> c-di-GMP formation

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6
Q

What do c-di-GMPs bind to? Why are they activated?

A

to many different effector proteins, generally involved in motile → sessile/biofilm lifestyle switch

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7
Q

What are the c-di-GMPs generally involved in?

A

generally involved in motile → sessile/biofilm lifestyle switch

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8
Q

What is the conserved motif of DGCs found in bacteria?

A

GGDEF

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9
Q

What are the conserved PDE motifs of bacterisa?

A

motifs EAL or HD-GYP

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10
Q

What do the conserved GDC and PDE motifs of bacteria allow?

A

allowing response to many different signals e.g. > 40 DGC + PDE proteins in Pseudomonas

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11
Q

What 2 things can environmental and cellular signals change?

A

-Change expression of DGCs and PDEs

-Change the enzymatic activity of existing DGCs and PDEs (often have N-term sensory domains, allow for the detection or reception of a signal)

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12
Q

What does increased expression of DGCs cause?

A

increased cyclic-di-GM levels

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13
Q

What is an example of a change in enzymatic activity of DGCs and PDEs?

A

signal induced dimerization of DGCs (PleD) with PleD

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14
Q

What is PleD?

A

2-component system response regulator protein

diguanylate cyclase

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15
Q

How does PleD interact with DGC? (SIGNAL INDUCED DIMERISATION OF dgcS)

A

sensor kinase, detects signal

phosphorylation of the receiver end of PleD and 2 PleD monomers can join together (dimerize)

receiver domains have dimerised

Now the 2 GGDEF domain can come together

Can form an intact cyclic-di-GMP synthesis active site

Activation of DGC and make cyclic-di-GMP

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16
Q

How CAN c-di-GMP bind diverse receptors?

A

heir effectors which bind have a PilZ domain

17
Q

How can c-di-gmp change the effector protein allosterically?

A

changes in their activity allosterically

18
Q

What can the c-di-GMP bound effectors directly control?

A

directly control target processes including transcription, proteolysis, enzyme activity and flagella function

19
Q

What is an example of c-di-GMP bound to effector protein and controls a target process?

A

c-di-GMP bound to BcsA, involved in cellulose synthesis.

The BcsA has a PilZ domain which can allosterically bind c-di-GMP.

activates the BcsA complex and see production of cellulose

20
Q

How many DGCs, PDEs and c-di-GMP-binding effectors in one organism?

A

MANY

21
Q

What does multiple DGCs, PDEs and c-di-GMP-binding effectors in one organism allow?

A
  1. allows many signals to be integrated
  2. several different regulatory pathways may operate in parallel through spatial or temporal segregation (specific localisation in large complexes, expressed at different times)
  3. in some cases, inactive GGDEF or EAL domains may act as effectors (bind c-di-GMP and interact with target proteins)
22
Q

What does several different regulatory pathways being operated allow?

A

the proteins of one specific pathway can be specifically localised together in a large protein complex.

or expressed at different times.
This resolves the conundrum of how same small molecule can be involved in different regulatory pathways.

23
Q

What can actvate diffeent c-di-GMP effectors?

A

concentration of c-di-gmp in the cell

24
Q

When can GGDEF or EAL domains act as effectors?

A

wen thy are inactive

bind c-di-GMP and interact with target proteins

no catalytic activity

binds target proteins in c-di-GMP dependent manner.

25
Q

Why is the role of c-di-GMP universal?

A

switch from motile to sessile/biofilm lifestyle

‘Universal’ role for c-di-GMP is in controlling motile → sessile/biofilm transition, often in co-ordination with related lifestyle switches

26
Q

What does low c-di-GMP promote?

A

virulence

motility

27
Q

What does high levels of c-di-GMP promote/activate?

A

sessility and biofilm formation

cell cycle progression

28
Q

What does the cell do when activating virulence?

A

Acute virulence, secretion of virulence factors, invasion, host adherence, immune modulation, cytotoxicity

29
Q

What dos the bacteria do when promotig motility?

A

Expression, assembly & activity of flagella, swimming & swarming

30
Q

What does the bacteria do when promoting sessility and biofilm formation?

A

Synthesis of adhesins and extracellular polysaccharides

31
Q

What does the cell do when c-di-GMoP promotes cell cycle progression?

A

e.g. asymmetric cell division in Caulobacter crescentus
`

32
Q

In reality is c-di-gmp one switch?

A

No, complex multistage process with complex regulatory steps

33
Q

What can effect the regulation of c-di-GMP?

A

environmental factors

extrinsic

biofilm

34
Q

How is motility inhabited/activated?

A

c-di-GMP-bound YcgR inhibits flagellar motor

PdeH promotes motility by ↓c-di-GMP

35
Q

How is biofilm formation and cellulose activated? (increased c-di-GMP)

A

↑ c-di-GMP induces production of biofilm components Curli fibres and cellulose

c-di-GMP binds & activates cellulose synthase
c-di-GMP-DgcM/PdeR induce curli expression.

Can also induce biofilm formation by inducing polysaccharide PGA.

c-di-GMP binds and activates Pga complex

36
Q

What biofilm components does increased c-di-GMP promote?

A

components and cellulose.

37
Q

What is the effect of low phosphate on c-di-GMP and biofilm formation?

A

Low phosphate induces ↓c-di-GMP and biofilm dispersal

↓c-di-GMP releases LapG from LapD, LapG cleaves LapA adhesin.

38
Q

In reality how does c-di-GMP regulate cell status?

A

multi-stage process with complex regulatory steps

L4 Molecular Microbiology (53 decks)

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