The Bacterial Flagellum

What are the 3 main parts of the flagellum?

1) Filament 2) Hook 3) Basal body

What are the 3 main types of flagellar genes? What are they named after?

1) Fla- 2) Mot- 3) Che- Named after the null phenotypes of the mutants

Flagellar Synthesis

Complex process involving many genes. New flagellin molecules transported through the hollow filament using Type III like secretion system. Subunits self-assemble with help of filament cap at tip, not base.

How does flagellar rotation occur?

Proton gradient in the periplasm causes protons to flow through the stator "channel"

Chemotaxis

Bacteria move toward or away from substances in their environment by this nonrandom process

How does bacterial flagella move forward and change direction?

CCW rotation causes forward motion (run) CW disrupts run causing cell to stop and tumble

Filament of flagellum

Extends from cell surface to the tip. It is the hollow, rigid cylinder of flagellin protein

T/F: During chemotaxis, bacteria move directly to or away from the stimulus.

False. It is not a straight line. Bacteria have "runs" and "tumbles". It eventually causes a "net movement"

Peritrichous

Flagellum all over

Mot- Flagellar Gene

Flagellum, but not rotation

Wavelength

Length of a light ray

Hook of flagellum

Links filament to basal body

Negative Chemotaxis

Net result is movement away from the repellent

Positive Chemotaxis

Net result is movement towards the attractant (nutrients)

Fla- Flagellar Gene

No/incomplete flagellum

Amphitrichous

One flagellum at each end

Che- Flagellar Gene

Rotation, but not reversal or chemotaxis

Basal body of flagellum

Series of rings that drive flagellar motor

Monotrichous

Single flagellum at one end

What is the purpose of flagella and swimming?

Swimming keeps bacteria in optimal environment, using tactic responses to chemo, photo, osmo, and thermo stimulation

Resolution

The ability of the lends to distinguish two items as two separate things, i.e. two dots as two separate dots

T/F: In chemotaxis, with more bound receptors, there is a longer run in the same direction.

True

The shorter the wavelength, the ____ the resolution

greater