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Microbial Physiology > Lecture 1B: Cell Locomotion > Flashcards

Lecture 1B: Cell Locomotion Flashcards

1
Q

What allows prokaryotic cells to move in their environments?

A

Motility devices that allow them to swim or crawl

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2
Q

What are the two major types of prokaryotic cell movement? (2)

A

Swimming and gliding

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3
Q

What is the phenomenon called when motile cells move toward or away from stimuli?

A

Taxis

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4
Q

What structure do many Bacteria use for swimming motility?

A

Flagellum

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5
Q

What is the analogous structure to flagella found in many Archaea?

A

Archaellum (pl. archaella)

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6
Q
  • Tiny rotating machines that push or pull the cell through a liquid
  • long, thin, appendages
A

flagella

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7
Q

What is the typical width of the appendages of bacterial flagella?

A

15–20 nm

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8
Q

How can flagella be observed under a microscope? (2)

A
  • light microscopy
  • electron microscopy
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9
Q

Different arrangements of flagella (4)

A
  • polar
  • lophotrichous
  • amphitrichous
  • peritrichous
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10
Q

Flagella are attached at one or both ends of a cell.

flagellation

A

polar flagellation

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11
Q

What is a group of many flagella (tuft) called?

flagellation

A

Lophotrichous flagellation

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12
Q

Tufts of flagella emerge from both poles of the cell

flagellation

A

amphitrichous flagellation

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13
Q

flagella located inserted around the cell surface

flagellation

A

peritrichous flagellation

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14
Q

The strength of the proton motive force affects the __ of flagella.

A

rotational speed

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15
Q

What is the maximum rotational speed of flagella?

A

Up to 1000 revolutions per second

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16
Q

What swimming speed can bacteria achieve relative to their size?

A

Up to 60 cell-lengths/sec

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17
Q

How do the swimming motions of peritrichously flagellated organisms differ from polarly flagellated organisms?

A
  • Peritrichously flagellated organisms move slowly in a straight line
  • Polarly flagellated organisms move more rapidly and continuously
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18
Q

True or False: Flagella rotate at a constant speed.

A

False

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19
Q

What is the significance of motility for prokaryotic cells?

A

Allows cells to reach different parts of their environment for resources or protection.

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20
Q

Flagellar structure and activity:
- __ in shape
- consists of several components
- filament composed of __
- __ rotating machine

A
  • helical
  • flagellin
  • reversible
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21
Q

What is the main part of the bacterial flagellum called?

A

Filament

The filament is composed of many copies of a protein called flagellin.

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22
Q

What protein is the filament of the bacterial flagellum primarily composed of?

A

Flagellin

The amino acid sequence of flagellin is highly conserved in Bacteria.

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23
Q

What does the hook connect in the structure of the flagellum?

A

The filament to the flagellum motor in the basal body

The hook consists of a single type of protein.

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24
Q

In bacterial flagella, which rings are found in the basal body? (4)

A

L ring, P ring, MS ring, C ring

The L ring is embedded in the LPS, P ring in peptidoglycan, MS ring in the cytoplasmic membrane, and C ring in the cytoplasm.

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25
Q

What function do Mot proteins serve in the flagella?

A

They function as the flagellar motor (stator)

Mot proteins are embedded within the cytoplasmic membrane and peptidoglycan.

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26
Q

True or False: The flagellar motor is a reversible rotating machine.

A

True

It is composed of more than 25 proteins and is anchored in the cytoplasmic membrane and cell wall.

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27
Q

What is the main energy source for the rotation of the flagellum?

A

Proton motive force

Rotation is thought to be caused by a ‘proton turbine’ process.

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28
Q

Fill in the blank: The rotor of the flagellar motor consists of the central rod and the _______.

A

L, P, C, and MS rings

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29
Q

What role do protons play in the function of the flagellar motor?

A

They flow through the Mot proteins, exerting electrostatic forces that cause rotation

About 1200 protons are translocated by each rotation of the flagellum.

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30
Q

What two main components make up the flagellum motor?

A

Rotor and stator

The rotor includes the central rod and various rings, while the stator is comprised of Mot proteins.

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31
Q

How does the rotational speed of the flagellum relate to proton flow?

A

It is set by the proton flow rate through the Mot proteins

The flow rate is a function of the intensity of the proton motive force.

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32
Q

What structural adaptations can microbes make to their flagellar motors?

A

Adding or subtracting subunits from the stator and C ring

This changes the ‘gear ratio’ of the motor.

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33
Q

What are the components of the flagellar motor that help generate torque?

torque - a measure of the force that can cause an object to rotate about an axis

A

Mot proteins

These surround the rotor and function to generate torque.

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34
Q

What is a unique feature of the flagellar motor in gram-positive bacteria?

A

Only the inner pair of rings is present

Gram-positive bacteria lack an outer membrane. Only MS and C rings are present

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35
Q

What role do genes play in flagellar synthesis in Bacteria?

A

Several genes encode the motility apparatus, with over 50 genes linked to motility in Escherichia and Salmonella species

These genes encode structural proteins, export proteins, and regulatory proteins.

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36
Q

How does the flagellar filament grow?

A

from its tip, not its base

This is different from the growth of animal hair.

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37
Q

What is the first component synthesized in flagellar assembly?

A

The MS ring is synthesized first and inserted into the cytoplasmic membrane

Following the MS ring, other anchoring proteins, the hook, and the cap are synthesized.

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38
Q

What is the role of the export apparatus in flagellar synthesis?

A

The export apparatus shuttles flagellin molecules into a 3-nm channel through the basal body and hollow flagellar filament

This process facilitates the export of flagellin synthesized in the cytoplasm.

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39
Q

How many flagellin protein molecules are needed to make one filament?

A

Approximately 20,000 flagellin protein molecules

This large number indicates the complexity of flagellar structure.

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40
Q

Fill in the blank: Cap proteins assist flagellin molecules to assemble in the proper fashion at the _______.

A

flagellum tip

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41
Q

What happens to broken flagella?

A

Broken flagella still rotate and can be repaired with new flagellin units

New units are passed through the filament channel to replace lost ones.

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42
Q

True or False: The flagellum grows continuously until it reaches its final length.

A

True

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43
Q

What are the main components synthesized during flagellar assembly? (5)

A

The main components are:
* MS ring
* C rings
* Hook
* Cap
* Flagellin subunits

These components work together to form the complete flagellum.

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44
Q

Protein in the flagellar structure responsible for proton motive force

A

Mot protein (stator)

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45
Q

Protein in the flagellar structure that acts as a motor switch (counter-clockwise and clockwise)

A

FliF proteins

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46
Q

These two (2) proteins in the flagellar structure act as the motor (the engine of the flagellum).

A
  • FliF protein
  • Mot protein
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47
Q
  • Composed of the FliF protein.
  • Provides a scaffold for the assembly of other flagellar components, such as the C ring (cytoplasmic ring), motor proteins (MotA/MotB), and the export apparatus.
  • a supramolecular complex embedded in the cytoplasmic membrane.
  • membrane/supra membrane (MS) ring
A

MS ring

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48
Q

Ring in the flagellar structure the secures that rod on the periplasmic space/peptidoglycan.

49
Q

Regulates the expression of the two outer-membrane porins OmpF and OmpC in response to changes in osmolarity.

Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

A

EnvZ/OmpR pathway

This pathway involves a membrane-bound histidine protein kinase (HPK) EnvZ and a response regulator (RR) OmpR.

50
Q

Senses changes in the redox state of components of the respiratory electron-transport chain

Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

A

ArcB–ArcA HAP system

The HPK ArcB contains a PAS domain that plays a crucial role in this sensing mechanism.

51
Q

Phosphoryl group transfer in the ArcB–ArcA system:

From a conserved His in the __ domain to a fused __ domain, then to a fused __ domain, and finally to DNA-binding __ __

What does this process regulate?; Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

A
  • ArcB kinase
  • RR
  • histidine-containing phosphotransfer (HPt)
  • RR ArcA

This process results in the regulation of microaerophilic gene expression by ArcA.

52
Q

What are the domains of the soluble HPK CheA in the chemosensory pathway of E. coli?

Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

A

Five domains designated P1–P5 from the N terminus to the C terminus

CheA senses changes through transmembrane chemoreceptors, which induce trans-autophosphorylation.

53
Q
  1. What are the two response regulators that compete for the phosphoryl group in the chemosensory pathway? (2)
  2. A motor-binding protein controlling flagellar motor switching.
  3. Controls the adaptation of the chemoreceptors.

Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

A

1.1 CheY
1.2 CheB
2. CheY
3. CheB

54
Q

Sporulation regulation of Bacillus subtilis:
- A single-domain RR regulated by two HPKs, KinB and KinA
- indirectly phosphorylates a DNA-binding RR, __, via a His residue in __.

Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

A

SpoOF
- Spo0A
- Spo0B

55
Q

Sporulation regulation:
HPK __ have numerous transmembrane domains. __, the other HPK, is soluble and has numerous PAS domains.

Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

56
Q

In the context of histidine–aspartate phosphorelay systems, what does the acronym HAMP stand for?

Function of HAMP?; Domain Organization of Histidine-Aspartate-Phosphorelay (HAP) Systems in Escherichia coli

A

Histidine kinases, adenylyl cyclases, methyl-binding proteins, and phosphatases

The HAMP domain serves as a linker domain in these systems.

57
Q

True or False: HPKs are shown as dimers for simplicity in the figure.

A

False

Despite being dimeric in nature, HPKs are depicted as monomers in the figure.

58
Q

What does the light-green rectangle represent in the figure?

A

Conserved, phosphorylatable His residues

This visual representation helps identify key residues involved in phosphorylation.

59
Q

Fill in the blank: The phosphoryl group in the ArcB–ArcA system is passed to a DNA-binding RR called _______.

60
Q

What is the flagella analog in Archaea?

A

Archaellum

61
Q

How does the archaellum impart movement to the cell?

62
Q

How does the archaellum compare in size to bacterial flagella?

A

Half the diameter

63
Q

What is the approximate width of an archaellum?

A

10–13 nm

64
Q

How do the filament proteins of archaella differ from bacterial flagellin?

A

Multiple proteins, no sequence homology

65
Q

How many genes typically encode the major proteins of the archaellum?

A

7–12 genes

66
Q

Name an archaeon known for its salt-loving nature and archaella studies.

A

Halobacterium

67
Q

Name a heat- and acid-loving archaeon with well-studied archaella.

A

Sulfolobus

68
Q

Name a methane-producing archaeon known for fast swimming.

A

Methanocaldococcus

69
Q

What is the fastest known organism on Earth?

How fast?

A

Methanocaldococcus

500 cell lengths per second; 50 times faster than Halobacterium; 10 times faster than E. coli

70
Q

What is one hypothesis for why archaella may generate less torque than flagella?

A

Smaller diameter

71
Q

What bacterial structure is the archaellum structurally related to?

A

Type IV pili

72
Q
  • What energy source drives archaella rotation?
  • What energy source powers the archaellum?
A
  • ATP
  • ATP hydrolysis
73
Q

How does the archaellum rotate?

A

Clockwise and counterclockwise

74
Q

What energy source powers bacterial flagella?

A

Proton motive force

75
Q

How do archaella and flagella differ in energy mechanisms?

A

ATP vs. proton motive force

76
Q

What does the difference in energy mechanisms suggest about motility evolution?

A

Independent evolution in Bacteria and Archaea

77
Q

Around how many billion years ago did Bacteria and Archaea diverge?

A

3.5 billion years ago

78
Q

What type of motility do bacteria use if they lack flagella?

A

Gliding motility

79
Q

How does gliding motility compare to flagellar motility?

A

Slower and smoother

80
Q

What cell shape is typical of gliding bacteria?

A

Filamentous or rod-shaped

81
Q

What is required for gliding motility to occur?

A

Solid surface contact

82
Q

Name a cyanobacterium that exhibits gliding motility.

A

Oscillatoria

83
Q

What gram-negative bacteria use gliding motility? (3)

A
  • Myxococcus
  • Cytophaga
  • Flavobacterium
84
Q

Are there any known gliding Archaea?

85
Q

How do cyanobacteria achieve gliding motility?

A

Slime secretion

86
Q

What is the role of type IV pili in gliding motility?

A

Extension and retraction drag the cell

87
Q

Which bacterium uses both type IV pili and an adhesion complex for gliding?

A

Myxococcus xanthus

88
Q

What is unique about Flavobacterium gliding motility?

A

No slime or pili; uses protein ratcheting

89
Q

What energy source drives Flavobacterium gliding?

A

Proton motive force

90
Q

How does gliding motility help bacteria ecologically?

A

Resource exploitation and cell interaction

91
Q

What is the directed movement of a microorganism in response to a stimulus called?

92
Q

What is the movement of bacteria toward or away from chemicals?

A

Chemotaxis

93
Q

What type of taxis is a response to light?

A

Phototaxis

94
Q

Why is taxis important for bacteria?

A

Resource access, avoidance of harm

95
Q

What are the two types of movements in peritrichously flagellated bacteria?

A

Runs and tumbles
| clockwise and counterclockwise: If the flagellum is rotating counterclockwise, it pushes the bacterium forward (run). When it rotates clockwise, it pulls the bacterium backward (tumble).

96
Q

In which direction do flagella rotate during a run?

A

Counterclockwise

97
Q

What happens when the flagella rotate clockwise?

98
Q

How do bacteria determine the direction of movement?

A

Temporal sensing

99
Q

What proteins detect attractants and repellents?

A

Chemoreceptors

100
Q

What happens to runs in the presence of an attractant?

A

Longer, fewer tumbles

101
Q

What movement pattern do bacteria follow in the absence of a gradient?

102
Q

What happens when a bacterium moves toward a repellent?

A

More frequent tumbles

103
Q

What type of flagella arrangement does E. coli have?

A

Peritrichous

104
Q

What type of movement do polarly flagellated bacteria like Pseudomonas use instead of tumbling?

105
Q

What bacterial genus uses flagellar stopping and Brownian motion for reorientation?

A

Rhodobacter

106
Q

What is the method used to measure chemotaxis with a small tube?

A

Capillary tube assay

107
Q

In a capillary tube assay, what happens when an attractant is inside the tube?

A

Bacteria accumulate

108
Q

What form of taxis leads bacteria toward oxygen?

109
Q

What part of a bacterial cell transmits sensory signals for movement?

A

Flagellar motor

110
Q

If a repellent is inside the capillary, what happens to the bacterial count?

Capillary tube assay

111
Q

What do bacteria typically follow in natural environments?

A

Nutrient gradients

112
Q

What microbial byproducts often attract bacteria?

A

Organic compounds, oxygen

113
Q

What bacterial pigments absorb light for phototaxis? (2)

A
  • Bacteriochlorophylls
  • carotenoids
114
Q

What is the name of light-induced taxis where cells tumble upon entering darkness?

A

Scotophobotaxis

115
Q

What sensor initiates phototaxis?

A

Photoreceptor

116
Q

What is the bacterial movement toward oxygen called?

117
Q

What taxis involves movement toward or away from high ionic strength?

118
Q

What taxis allows cyanobacteria to move toward water?

A

Hydrotaxis

Microbial Physiology (5 decks)

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