Bacterial flagella and chemotaxis

What us Brownian motion (pedesis)?

Random moving of particles in a fluid

What is motility?

It is controlled, self-propelled movement

What is motility mediated by? Which one is most efficient?

1. Pili

2. Adhesins

3. Flagella (most efficient)

What is adhesion mediated gliding motility?

This is where bacteria have sticky molecules on the surface which allow them to twist and adhere to surfaces over time

Do gram positives or gram negatives have flagella? Compared to the bacterial cell, is it larger or smaller? How is the flagella connected?

Both do and is larger than the bacterial cell. It is anchored via the cell wall in both.

What are flagella?

They are prokaryote structures that allow efficient motility. They are long, thin, and whip-like appendages that move the bacteria in response to environmental signals (attractants and repellents)

What is atrichous?

Bacteria that lack flagella

What is monotrichous?

A single flagellum located at end

What is amphitrichous?

A single flagellum at both ends of the bacteria

What is lophotrichous?

Multiple flagella at one end

What is amphiliphotrichous?

Multiple flagella at both ends

What is peritrichous?

Multiple flagella covering the entire cell

What are the 3 components of the flagella structure?

1. Filament (propeller)

2. Hook (universal joint)

3. Basal body

What is the filament made of?

Flagellin

What is the hook?

It is a flexible linker that allows the filament to rotate while pointing in any direction outside of the cell.

What is the basal body? What does it consist of?

It is a transmembrane motor (rotary motor) that is anchored to the cytoplasmic membrane and cell wall. It consists of a central rod that passes through a series of rings.

How is the flagella linked to the cell wall?

Through Mot proteins that associate with the basal body

How is the flagella linked to the cytoplasm in gram positive and gram negative?

Through the rings on the bottom

What is a difference between flagella structure in gram positives vs gram negatives?

Gram negative have an extra membrane (OM) that the flagella has to be bound to. Therefore they have extra rings (L and P only found in gram negative).

What rings are found in both gram positive and gram negative?

MS and C ring

Where is the L ring anchored?

Outer membrane

Where is the P ring anchored?

Peptidoglycan

Where is the MS rings? What is the M ring attached to? S?

Within the cytoplasmic membrane. S ring is attached to the inner thick layer of peptidoglycan. M ring is attached to the cell membrane

What does the C ring allow access to?

Cytoplasmic controls

What is the flagella like? Is it a highly controlled process? Do the membranes rip apart when the flagella rotates?

It is like an electric motor. Yes it is and no the membranes stay in tact.

What structural components of the flagella move (rotor)?

1. C ring

2. MS ring

3. Rod (filament that goes through)

4. Filament

5. Hook

What structural components of the flagella do not move (stator)?

1. Mot proteins

2. P ring

3. L ring

What does FliG interact with? Where is it found?

In the C-ring and it interacts with the Mot proteins which generate the twisting

In gram negatives what do the P and L rings form?

A pore through the peptidoglycan and outer membrane that let the rod pass

What does FliM do? Where is FliM found?

It is where the signal comes in to bind and changes the conformation of the Mot proteins. Found in the C ring

What is flagellar motility driven by?

Proton motive force which needs energy (ATP)

What happens as protons flow into the cell?

The Mot proteins will change their conformation and generate twisting of the flagellum as Mot complex will allow the passage of protons into the cell through the motor.

What forms the Mot complex?

Multiple copies of MotA and MotB

Where are the MotA and MotB proteins found?

Anchored to the peptidoglycan and they surround the MS ring