Write detailed notes on a) The regulation of motility in Escherichia coli

The regulation of motility in Escherichia coli

Answer:

mediated by flagella,

allow the bacterium to swim in liquid environments.

highly coordinated

involves genetic control of flagellar synthesis and behavioral control through chemotaxis.

The regulation of motility in Escherichia coli

Answer:

Motility in Escherichia coli is primarily mediated by

flagella, which allow the bacterium to swim in liquid environments.

The regulation of motility in Escherichia coli

Answer:

Motility in Escherichia coli is primarily mediated by flagella, which allow the bacterium to swim in liquid environments.

The regulation of motility in E. coli is

highly coordinated

The regulation of motility in Escherichia coli

Answer:

Motility in Escherichia coli is primarily mediated by flagella, which allow the bacterium to swim in liquid environments.

The regulation of motility in E. coli is highly coordinated and involves

both genetic control of flagellar synthesis and behavioral control through chemotaxis.

main points listed

Genetic Regulation of Flagellar Synthesis

Chemotaxis Regulation (Behavioral Control)

Environmental and Global Regulation

Energy Dependence

Genetic Regulation of Flagellar Synthesis main points listed

Class I Genes

Class II Genes

Class III Genes

Chemotaxis Regulation (Behavioral Control) main points listed

• Methyl-accepting chemotaxis proteins (MCPs)

• Che Proteins

Environmental and Global Regulation main points listed

• Catabolite repression (CRP-cAMP system):

• Oxygen and nutrient levels:

• Biofilm formation and quorum sensing:

Genetic Regulation of Flagellar Synthesis intro

regulated in a hierarchical manner

involves the expression of more than 50 genes,

grouped into three classes

Genetic Regulation of Flagellar Synthesis

Class I Genes:

• The flhDC operon encodes the FlhD and FlhC proteins.

• form the FlhD₄C₂ complex,

• master regulator for flagellar gene expression.

• activates transcription of Class II genes.

Genetic Regulation of Flagellar Synthesis

Class I Genes:

• The flhDC operon encodes

• the FlhD and FlhC proteins.

Genetic Regulation of Flagellar Synthesis

Class I Genes:

• The flhDC operon encodes the FlhD and FlhC proteins.

  • These proteins form

• the FlhD₄C₂ complex,

Genetic Regulation of Flagellar Synthesis

Class I Genes:

• The flhDC operon encodes the FlhD and FlhC proteins.

  • These proteins form the FlhD₄C₂ complex, which acts as

• the master regulator for flagellar gene expression.

Genetic Regulation of Flagellar Synthesis class I Genes:

• The flhDC operon encodes the FlhD and FlhC proteins.

• These proteins form the FlhD₄C₂ complex, which acts as the master regulator for flagellar gene expression.

  • This complex does what

• activates transcription of Class II genes.

Genetic Regulation of Flagellar Synthesis

Class II Genes:

• structural components of the basal body and hook,

• regulatory factors ( fliA and flgM.)

• fliA , sigma factor σ^28, for the transcription of Class III genes.

• flgM , anti-sigma factor , inhibits σ^28 until the hook-basal body structure is complete.

genetic Regulation of Flagellar Synthesis

Class II Genes:

Include

structural components of the basal body and hook,

regulatory factors such as fliA and flgM.

genetic Regulation of Flagellar Synthesis

Class II Genes:

fliA

encodes sigma factor σ^28,

required for the transcription of Class III genes.

genetic Regulation of Flagellar Synthesis

Class II Genes:

flgM

encodes an anti-sigma factor

inhibits σ^28 until the hook-basal body structure is complete.

genetic Regulation of Flagellar Synthesis

Class III Genes:

• encode components of the filament and motor proteins.

• Expression activated once σ^28 is released

genetic Regulation of Flagellar Synthesis

Class III Genes:

These encode

components of the filament (e.g., fliC for flagellin)

and motor proteins.

genetic Regulation of Flagellar Synthesis

Class III Genes:

Expression is activated once

σ^28 is released from FlgM inhibition.

genetic Regulation of Flagellar Synthesis

This hierarchical regulation ensures that

flagellar components are synthesized in the correct order.

Chemotaxis Regulation (Behavioral Control)m intro

Motility behavior modulated through a chemotaxis system

cell move toward attractants and away from repellents.

This system consists of MCPs and Che proteins

Chemotaxis Regulation (Behavioral Control)m intro

what s modulated through a chemotaxis system

Motility behavior in E. coli i

Chemotaxis Regulation (Behavioral Control) intro

Motility behavior in E. coli is modulated through a chemotaxis system that enables

the cell to move toward attractants and away from repellents.

Chemotaxis Regulation (Behavioral Control)
Motility behavior in E. coli is modulated through a chemotaxis system that enables the cell to move toward attractants and away from repellents.

This system consists of the following components:?

MCPs

Che protrins

main point 2

Chemotaxis Regulation (Behavioral Control)

Methyl-accepting chemotaxis proteins (MCPs):

• Act as sensory receptors and detect environmental signals.

main point 2

Chemotaxis Regulation (Behavioral Control)

(MCPs):

Methyl-accepting chemotaxis proteins

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins:

A

Y

Z

R

B

W

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins: CheA:

Histidine kinase that autophosphorylates upon MCP stimulation.

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins: CheY: WHAT IS IT

Response regulator

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins: CheY: when phosphorylated (CheY-P)

interacts with the flagellar motor to induce clockwise (CW) rotation,

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins: CheY:

• Response regulator that, when phosphorylated (CheY-P), interacts with the flagellar motor to induce clockwise (CW) rotation, leading to

• tumbling.

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins: CheZ:

Dephosphorylates CheY-P,

promoting counterclockwise (CCW) rotation,

results in smooth swimming or running.

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins: CheR and CheB:

Involved in receptor methylation and demethylation,

adjusting the sensitivity of the system to persistent stimuli.

main point 2

Chemotaxis Regulation (Behavioral Control)

Che Proteins: CheW:

Couples CheA to MCPs.

main point 2

Chemotaxis Regulation (Behavioral Control)

The balance of CheY-P determines

the pattern of swimming (CCW) and tumbling (CW),

main point 2

Chemotaxis Regulation (Behavioral Control)

The balance of CheY-P

allowing the cell to navigate chemical gradients.in response to environmental signals.

MAIN POINT 3 Environmental and Global Regulation

influenced by environmental and metabolic cues:

CRP-cAMP system

Oxygen and nutrient levels:

biofilm formation

quorum sensing

main point 3

environmental and global regulation

Catabolite repression (CRP-cAMP system):

When glucose is abundant, cAMP levels are low, reducing CRP activity and repressing flhDC expression, thereby inhibiting motility.

main point 3

environmental and global regulation

Oxygen and nutrient levels:

• Motility is promoted under nutrient-poor conditions as the cell searches for more favorable environments.

main point 3

environmental and global regulation

Biofilm formation and quorum sensing:

.

• These signals often downregulate motility genes and promote surface adhesion and community behavior

main point 4

Energy Dependence

flagellar motor

powered by (PMF)

across the cytoplasmic membrane

motility is energetically regulated

linked to cellular respiration and energy availability.

main point 4

Energy Dependence

The flagellar motor

powered by the proton motive force (PMF)

across the cytoplasmic membrane.

main point 4

Energy Dependence

This ensures that motility is

energetically regulated and linked to cellular respiration and energy availability.

Conclusion:

multi-layered process

transcriptional control,

signal transduction,

energy management.

bacterium adapt to changing environmental conditions

coordinating structural development and behavioral responses.

Conclusion:

The regulation of motility in E. coli is a multi-layered process involving .

transcriptional control, signal transduction, and energy management

Conclusion the regulation of motility

It allows the bacterium to

efficiently adapt to changing environmental conditions by coordinating structural development and behavioral responses.

INTRODUCTION

What mediates motility in Escherichia coli?
A:

Flagella, which allow swimming in liquid environments.

INTRODUCTION

Flashcard 2
Q: What two main systems regulate motility in E. coli?
A:

Genetic control of flagellar synthesis and behavioral control via chemotaxis.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Flashcard 3
Q: How is flagellar gene expression organized in E. coli?
A:

Hierarchically into Class I, II, and III genes.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class I Genes

Flashcard 4
Q: What is encoded by the flhDC operon?
A:

FlhD and FlhC proteins.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class I Genes

Flashcard 5
Q: What is the function of the FlhD₄C₂ complex?
A:

Acts as a master regulator, activating Class II gene transcription.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class II Genes

Flashcard 8
Q: What is the role of flgM?
A:

It encodes an anti-sigma factor that inhibits σ^28 until the hook-basal body is complete.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class II Genes

Flashcard 7
Q: What is the role of fliA and what does it encode?
A:

It encodes σ^28 (sigma-28), a sigma factor needed for Class III transcription.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class II Genes

Flashcard 6
Q: What do Class II genes encode?
A:

Basal body and hook components, and regulatory proteins like fliA and flgM.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class III Genes

Flashcard 11
Q: Why is hierarchical regulation important for flagellar synthesis?
A:

Ensures components are synthesized in the correct order.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class III Genes

Flashcard 10
Q: When is Class III gene expression activated?
A:

When σ^28 is released from FlgM inhibition.

1. GENETIC REGULATION OF FLAGELLAR SYNTHESIS

Class III Genes

Flashcard 9
Q: What do Class III genes encode?
A:

Components like flagellin (fliC) and motor proteins.They also include proteins essential for flagellar assembly and function.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

Flashcard 12
Q: What enables E. coli to move toward attractants or away from repellents?
A:

The chemotaxis system.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

MCPs (Methyl-accepting chemotaxis proteins)

Flashcard 13
Q: What is the role of MCPs?
A:

They act as sensory receptors detecting environmental signals.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

Che Proteins

Flashcard 19
Q: What determines whether E. coli swims or tumbles?
A:

The intracellular level of CheY-P.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

Che Proteins

Flashcard 18
Q: What is CheW’s function?
A:

It couples CheA to MCPs.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

Che Proteins

Flashcard 17
Q: What do CheR and CheB do?
A:

They methylate and demethylate receptors, adjusting sensitivity.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

Che Proteins

Flashcard 16
Q: What is the role of CheZ?
A:

Dephosphorylates CheY-P, promoting counterclockwise (CCW) rotation → smooth swimming.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

Che Proteins

Flashcard 15
Q: What does CheY-P do?
A:

Interacts with the flagellar motor to induce clockwise (CW) rotation → tumbling.

2. CHEMOTAXIS REGULATION (BEHAVIORAL CONTROL)

Che Proteins

Flashcard 14
Q: What does CheA do?
A:

It is a histidine kinase that autophosphorylates after MCP stimulation.

3. ENVIRONMENTAL AND GLOBAL REGULATION

Flashcard 22
Q: How does biofilm formation affect motility?
A:

It downregulates motility genes and promotes adhesion and community behavior.

3. ENVIRONMENTAL AND GLOBAL REGULATION

Flashcard 21
Q: How do nutrient levels affect motility?
A:

Motility increases under nutrient-poor conditions.

3. ENVIRONMENTAL AND GLOBAL REGULATION

Flashcard 20
Q: How does glucose affect motility?
A:

High glucose → low cAMP → reduced CRP activity → flhDC repression → less motility.

4. ENERGY DEPENDENCE

Flashcard 24
Q: Why is motility linked to cellular energy?
A:

Because it is powered by PMF, which depends on respiration and energy status.

4. ENERGY DEPENDENCE

Flashcard 23
Q: What powers the flagellar motor in E. coli?
A:

The proton motive force (PMF).

CONCLUSION

Flashcard 25
Q: What are the key regulatory layers controlling E. coli motility?
A:

Transcriptional hierarchy, chemotactic signaling, environmental inputs, and energy availability.

MEMORY AID

Flashcard 26
Q: What mnemonic can help remember the regulation levels of E. coli motility?
A:

"GC-Energy" = Genetic, Chemotaxis, and Energy-dependent regulation.