MBIO 1010 / Topic 2d: Microbial Locomotion

What are the two main types of motility in bacteria?

Flagellar motility and surface motility.

What are flagellum? What do they do? How can you see them?

Hollow protein filaments anchored in CM and extending through CW and OM (if latter is present), imparting motility. Seen with flagella stain, dark-field, and TEM.

What are the four types of bacteria based on their flagella?

• Monotrichous, having a single flagellum.

• Amphitrichous, having flagella at opposite ends.

• Lophotrichous, having multiple flagella in a single tuft.

• Peritrichous, hacing flagella distributed around the cell.

What are the three parts of a flagellum?

Filament, hook, and basal body.

What is the filament of a flagellum? How long is it? What is it made of?

RIgid helical protein that’s 20µm long. It is composed of identical protein subunits called flagellin.

What is the hook of a flagellum?

Flexible attachment between filament and basal body.

What does the basal body of a flagellum consist of? What are the four things it passes through in E. coli?

A central rod that passes through a series of rings. The series of rings being…

• L ring for LPS region.

• P ring for peptidoglycan region.

• MS ring for the cell membrane region.

• C ring for the cytoplasm region.

Where does flagella get their energy from to move? What are mot proteins, and how do they help here?

PMF. Mot proteins are proteins that help form a channel that allows protons to move into the cytoplasm, providing energy to flagellum.

What are the five steps to flagellar synthesis?

1. Basal body is made in CM and periplasm.

2. Hook is added to basal body.

3. Flagellin proteins are synthesized in cytoplasm.

4. Flagellin go through a 3nm channel in flagellum.

5. Cap protein adds each flagellin unit to growing filament.

What increases the speed or flagellar rotation? What’s the fastest it can move in terms of rotation per second and cell lengths per second.

Movement of protons in the PMF. Fastest it can go is 300 flagellar rotations per second and 60 cell lengths per second.

What is the pattern of movement of peritrichous flagella (which we can assume for all flagella and bacteria)?

1. Run: Forward motion. Counter-clockwise rotation in a bundle.

2. Tumble: Reverse motion. Clockwise rotation into a random new direction.

3. Repeat.

What is the flagella of Archaea called? What are the three things that makes it different from bacterial flagella? What is it more related to?

Archaellum, set apart from bacterial flagella by…

• Thinner filament.

• Fewer proteins forming basal body.

• Rotation is driven by ATP hydrolysis.

It is more related to type IV pilus.

What is a taxis? What are the five different types of taxis?

Directed movement in response to chemical or physical gradients. Its five types are…

• Chemotaxis: response to chemicals.

• Aerotaxis: response to oxygen.

• Osmotaxis: response to ionic strength.

• Hydrotaxis: response to water.

• Phototaxis: response to light.

In chemotaxis, what are attractants and repellants sensed by?

Chemoreceptors.

What is the movement pattern called in the absence of a chemical attractant? Will there by any net movement in the population?

Random walk. No net movement of population.

What is the movement pattern called in the presence of a chemical attractant? Will there by any net movement in the population? What is the duration of the tumble and run?

Biased random walk. Net movement of cells toward the attractant, even if other cells may head to the wrong direction. Tumble delayed, run longer.

How do you measure chemotaxis?

Insert a capillary tube containing a chemical into a medium containing motile bacteria, count bacteria.

• If more bacteria than control counted, attractant and movement towards attractant.

• If less bacteria than control counted, repellent and movement away from repellent.

What are the three other ways that bacteria can move? Collectively, what type of movement is this called? What do all ways of this need to move? Is it slower or faster than flagellar motility?

• Slime excretion.

• Twitching motility.

• Gliding.

Collectively called surface motility or gliding motility. It needs surface contact. Slower than flagellar motility.

How do bacteria move using slime excretion?

Excretes slime and uses slime as the surface to move along on.

What does bacteria require in order to perform twitching motility? How does bacteria move using this mechanism? Can only bacteria do this?

Requires type IV pilus, with its pilus extending, attaching, and retracting using hydrolysis of ATP. Bacteria and Archaea can do this.

What does gliding not need to move? What do they need to move? What is gliding’s energy source?

• It does not need any external propulsive structures.

• It needs three sets of proteins: stationary gliding motors, helical protein track, and extracellular adhesion proteins.

• Uses PMF to rotate.