2-Bacterial Energy Transport and Scavenging Flashcards

1
Q

What are ‘planktonic’ bacteria?

A

‘Free-flowing’ bacteria
In suspension
Not adherent/sessile (not in a biofilm)

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2
Q

What is a biofilm?

What functions does it have?

A

Biofilm = Structural community of bacteria cells enclosed in a self-produced polymeric matrix and adherent to a surface (Costerton & Co 1999)

It protects colony from dangers like bacteria

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3
Q

What is the process of biofilm formation?

A

1) Attachment - planktonic bacteria attach to surface
2) Micro-colony - bacteria dived and produce extracellular polymers
3) Mature Biofilm - when cells produce enough to form a polymeric matrix
4) Dispersal - nutrients run out or conditions change and cells revert to planktonic bacteria

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4
Q

Give 4 examples of processes that are monitored by bacteria

A

Self-monitoring - concentration of molecules within itself, e.g. Cyclic-di-GMP: high concentration=biofilm formation, low concentration = planktonic

Monitoring others/Intelligence gathering- quorum sensing, AHL’s

Motility- moving to better environment

Regulation of cellular processes - cell growth etc.

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5
Q

Give 5 examples of processes that a bacterial cell needs to carry out (and gain energy for)

A

1) Manufacturing - build cell components
2) Transport - import & export material
3) Surveillance - detect toxins / useful substances
4) Waste management - efflux systems
5) Energy Production - respiration, fermentation

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6
Q

What are the four stages of bacterial growth in batch culture?

A

1) Lag - growth is slow, bacteria adjust (change processes & gene expression) to suit new environment
2) Log- Increased production of cell components, cells rapidly divide
3) Stationary - toxins accumulate & nutrients run out, reduction in metabolic components and increase in components to deal with stress, no cell growth
4) Death- In culture, bacteria cannot move to find better environment, and bacteria die

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7
Q

What protein do E.coli use to produce ATP?

A

F-ATP synthase

  • Membrane bound
  • Has a rotating head
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8
Q

Describe how ATP is synthesised by this protein?

A

Protons from the periplasm pass through the F0 rotary motor
This causes the complex to rotate
Rotation causes ADP and Pi to be forced close enough to bond
Thus rotary motion is converted to chemical energy

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9
Q

What else are these proton-powered motors used for in some bacteria?

A

To run flagella-based motility systems

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10
Q

Name 5 types of cell transport

A

Facilitated Diffusion
Ion-coupled transport
Periplasmic-binding-protein (PBP) dependent ATP-drive
ATP-driven
Phosphoenolpyruvate (PTS), carbohydrate transfer system

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11
Q

Is facilitated diffusion passive or active?

A

Passive

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12
Q

What is a uniport system? Give one example.

A

Passive facilitated diffusion
Only one molecule is moving, via a membrane embedded protein (the facilitator)
Least common method of transmembrane transport

e.g. E.coli glycerol uniporter

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13
Q

What control do bacteria have over this uniport system diffusion?

A

None.

It is passive diffusion, no energy is used.
Diffuse can occur in both directions
Diffusion cannot go against the concentration gradient -> diffuses until equilibrium is reached.

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14
Q

What are symport-ion coupled systems?

Give and example

A

Ion and substrate pass in the SAME direction, through a symport protein.
Substrate requires an ion partner to pass through

E.g. Lac Permease

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15
Q

What is an antiport system?

A

Substrate and ion move in OPPOSITE directions.

Substrate requires a counter ion

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16
Q

Describe how a chemiosmotic circuit can be set up by ATP-ase, a symporter and an antiporter.

A

ATPase creates a proton gradient by pumping protons across the membrane
Symporter uses available ions (e.g. Na+) to transport substrate INTO the cell.
Antiporter uses the protons to pump the accumulated ions OUT of the cell.

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17
Q

What carbon source is preferred by bacteria and why?

A

Glucose

It is the easiest to metabolise and generates the most energy

18
Q

Give an example of a scavenging system turned on when glucose is not available.

A

The lac operon for the uptake and metabolism of lactose. Three genes, ensures uptake and breakdown are regulated together.

19
Q

What are the three parts of the lacZYA operon found in E.coli?
What are their functions?

A

LacZ protein gene = Beta-galastosidase (Lactase!), cleavage of lactose disaccharide into glucose + galactose

LacY permease gene = Beta- galactoside permease, symport transporter, uptake of lactose, membrane- embedded protein

LacA gene = Beta-galactoside transacetylase, catalyses the acetylation of galactosides, lactosides, glucosides…function still unknown!

20
Q

What two regions of the E.coli genome are responsible for transport and metabolism of lactose in the cell?

A

LacI repressor AND Lac operon

21
Q

What does the lac L repressor do?

A

It regulates operon activity upstream of the promotor

22
Q

Describe the lac Y permease protein.

A

Membrane embedded protein
Symport transporter (proton and lactose INTO cell)
Twelve transmembrane regions, 80% alpha helical

23
Q

Is there negative or positive transcriptional control on the lac operon?

A

Negative transcriptional control.

The repressor protein bound to the DNA inhibits initiation of transcription when there is no lactose present.

24
Q

What is an operon?

A

Genes sequences, promotor region AND operator/activator binding sites

25
Q

How is lactose entry via lacY mediated transport controlled?

A

When lactose binds to the LacY binding pocket, there is a salt bridge preventing its entry.
The salt bride occurs between anionic glutamic acid and cationic lysine.
Protons abundant on the periplasmic side
Protons balance negative glutamic charge, breaking the salt bridge
This allows lactose to enter AND the proton to move across the membrane INTO the cell
Lysine temporarily forms salt bridge with aspartic acid, however when proton not present the original salt bridge reforms resetting the system.

26
Q

What is a PTS system?

A

Phosphotransferase system
Distinct active transport system used when PEP (Phoshpoenolpyruvate) is the source of energy. (PEP is a glycolysis product)
Multi-compnent complex system
PEP energy is catabolised to transport a carbohydrate into the cell resulting in a pyruvate catabolite
Systems have specific components depending on the sugar being transported in.
Series of phosphorylation events from PEP energy source to the terminal acceptor which is the sugar being transported in.

27
Q

What first two steps are common to all PTS systems?

A

1) PEP is converted to pyruvate, and Enzyme 1 is phosphorylated
2) Enzyme 1 then phosphorylates Heat Stable Protein (Hpr)

28
Q

What does the addition of the phosphate to the substrate, once inside the cell do?

A

The added phosphate group prevents the substrate being recognised by the transporter maintaining a concentration gradient favouring import inside the cell.

29
Q

What is the second important function of PTS system in the cell?

A

Regulation of other sugar uptake systems like the lac operon.

30
Q

What does the removal of the lacI repressor protein by lactose do?

A

Lactose changes the structure causing it to detach from the operator sites
Allows lacZYA to be transcribed
It de-represses the lacZYA promotor only
It does NOT up-regulate the promotor

31
Q

What does dimeric CRP protein do?

A

It is the transcription factor needed to up-regulate the lacZYA promotor.
Forms the cAMP-CRP complex.
CRP = ‘Catabolic Repressor Protein’

32
Q

What does the cAPM-CRP complex do?

A

Binds to consensus sequence within the operator site.
cAMP-CRP consensus sequences found throughout the genome at promotors under control of this complex. => this set of genes = cAMP-CRP regulon

33
Q

What does adenylate cyclase do?

A

Converts ATP to cAMP

34
Q

What effect does glucose have on cAMP production?

A

It is repressed by glucose.

Low glucose= high enzyme activity = high cAMP , therfore high cAMP signals depletion of glucose

35
Q

What effect does HIGH glucose concentration have on EIIA and adenylate cyclase?

A

EIIA mainly unphosphorylated
Adenylate catalase is inactive

This results in no cAMP production, therfore no cAMP-CRP complex forms to activate lac transcription of cAMP-CRP activated genes. This inhibits lac permease and block lactose uptake.

36
Q

What effect does LOW glucose concentration have on EIIA and adenylate cyclase?

A

EIIA mainly phosphorylated

Adenylate catalase is active

37
Q

What does high cAMP concentration signal?

What happens when this occurs?

A

Depletion of glucose.

Scavenging systems are turned on to look for alternative energy sources

38
Q

What do cycles of methylation by Che R and demethylation by MCP’s allow bacteria to have?

A

‘short term memory’ and allow the system to be reset

e.g CheA phoshporylates CheY which interacts with FliM and suppresses tumbling. CheY is dephosphorylated by Che Z and system is reset.

Dephosphorylation of CheY by Che Z is extremely important allows system to reset and so it can respond to other ligand and different signal.

39
Q

CheY interaction with FliM motor protein causes tumbling to be promoted or suppresed?

A

Suppressed

40
Q

What does Che Z do to Che Y? What is the consequence of their interaction?

A

Che Z dephosphorylates Che Y.

Allows system to reset so a different ligand can be responded to.