Microbial Locomotion - Discussion 1

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Questions and Answers

What causes swimming motility in prokaryotic cells?

Cytoplasm streaming

Cilia

Pseudopodia

Flagella (correct)

Which of the following describes the structure of bacterial flagella?

Straight and rigid

Branching and multi-headed

Helical with a uniform wavelength (correct)

Flexible and coiled

What is the role of the proton motive force in bacterial flagella movement?

It creates torque for flagellar rotation. (correct)

It powers the synthesis of flagella.

It aids in the attachment of flagella to the cell.

It maintains the structure of the flagellar filament.

In which type of flagellation are flagella located at one or both ends of the bacterial cell?

Polar flagellation Signup and view all the answers

What is the main difference between bacterial and archaeal flagella?

Archaeal flagella are powered by ATP. Signup and view all the answers

How does the arrangement of flagella influence the swimming pattern of bacteria?

It determines the swimming pattern and speed. Signup and view all the answers

What is the first step in the synthesis of bacterial flagella?

Assembly of the MS and C rings Signup and view all the answers

What swimming pattern is typically associated with bacteria that have peritrichous flagella?

Erratic or tumbling swimming pattern Signup and view all the answers

What is gliding motility?

Movement without external appendages Signup and view all the answers

Which mechanism uses the secretion of a slimy substance for movement?

Slime Extrusion Mechanism Signup and view all the answers

How does the Type IV Pili Mechanism enable movement?

By extending and retracting pili Signup and view all the answers

What describes chemotaxis?

Movement in response to a chemical stimulus Signup and view all the answers

In peritrichously flagellated bacteria, what movement occurs when they tumble?

They stop and move in a random direction Signup and view all the answers

What is true phototaxis?

Movement toward areas with more light Signup and view all the answers

Which type of taxis is specifically related to the presence of oxygen?

Aerotaxis Signup and view all the answers

What does the capillary tube assay measure?

The movement of microorganisms in response to chemicals Signup and view all the answers

Study Notes

Introduction to Microbial Locomotion

Motility enables prokaryotic cells to navigate their environments.
Major prokaryotic cell movement types include swimming and gliding.

Swimming Motility

Flagella, measuring 15-20 nm, facilitate swimming motility in bacteria.

Types of Flagellation

Polar Flagellation: Flagella attached at one or both ends of a cell.
Peritrichous Flagellation: Flagella dispersed over the entire surface of the cell.

Flagellar Structure

Flagella are helical with a consistent wavelength.
Components include:
- Tip
- Filament
- Hook
- Motor: Comprising L, P, MS, and C Rings.
- Mot proteins
- Fli proteins

Flagellar Movement

Functions as a rotary motor allowing circular movement.
Structure includes rotor (central rod and rings) and stator (mot proteins).
Movement powered by the bacterial proton motive force.

Archaeal Flagella

Have a width of 10-13 nm.
Composed of various flagellin proteins and powered directly by ATP.

Flagellar Synthesis

Begins with assembly of MS and C rings in the cytoplasmic membrane.
Flagellin flows through the hook to form the filament; guided by cap proteins.

Speed and Motion Influences

Speed and movement direction depend on flagella type and arrangement.
Polar Flagella: Result in slow and linear swimming.
Peritrichous Flagella: Cause erratic or tumbling swimming patterns.

Mechanisms of Gliding Motility

Rod-shaped bacteria can glide without flagella, cilia, or pili.

Gliding Mechanisms

Slime Extrusion: Secretion of a slimy substance for propulsion.
Type IV Pili Mechanism: Involves retraction and extension of pili (e.g., Pseudomonas aeruginosa).
Protein Adhesion Complex: Forms a sticky adhesion allowing movement (e.g., Myxococcus xanthus).
Surface Protein Movement: Uses gliding-specific proteins for forward motion (e.g., Flavobacterium).

Chemotaxis

Directed movement in response to chemical stimuli.

Differences in Chemotaxis

Peritrichous Flagellated Bacteria: Exhibit runs (forward swimming) and tumbles (stopping and jiggles).
Polar Flagellated Bacteria: Can reverse flagella rotation to change movement direction.

Measuring Chemotaxis

Capillary Tube Assay:
- Controlled: No change in microorganism movement.
- Attractant: Microorganisms swarm towards chemical.
- Repellent: Microorganisms move away from chemical.

Phototaxis

True Phototaxis: Movement towards increasing light intensity.
Scotophobotaxis: Random swimming out of illuminated areas under a microscope.

Other Types of Taxes

Aerotaxis: Movement towards or away from oxygen.
Osmotaxis: Movement influenced by ion concentration.
Hydrotaxis: Movement towards or away from water.

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Description

This quiz focuses on the types of microbial locomotion, particularly in prokaryotic cells. Students will explore the mechanisms of motility such as swimming and gliding, as well as the role of flagella in swimming motility. Test your knowledge on these critical aspects of microbial movement.