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