3-Bacterial Motility and Chemotaxis Flashcards
What energy is used to cause flagella to rotate?
Proton-motor force
What occurs when flagella rotate anti-clockwise?
They bundle together and the bacterium is propelled forward.
What occurs when the flagella rotate clockwise?
The bundle of flagella unravels and bacteria ‘tumble’ -> they change direction
What is ‘random walk’ in bacteria and when does it occur?
When ration of run and tumble in bacteria is random and movement is random.
Occurs in a homogenous environment. (no concentration gradient)
In presence of an environmental gradient is the ratio of tumble in favour of tumble or run?
In favour of run. Bacteria wants to move toward the good.
When it wants to stay, tumble is favoured.
What are the 5 general components of the flagellar motor structure?
1) Filament
2) Hook
3) Busher
4) Stater
5) Rotor
What is the filament?
The propellor
Hollow rigid cylinder made of subunits of the protein flagellin
What is the Hook?
The universal joint, allows torque generated by motor complex to change angle and direct filament orientation.
Links filament to the basal body.
What two rings is the ‘Bushing’ made of and what do they do?
L&P rings
L ring = outermembrane, p ring = cell wall, together acts as ‘bearing’ to allow motor to rotate without damaging the cell wall
What is the stator made of and what does it do?
Made of studs and C rings
It is the fixed point of the system, sits in the cell membrane
The MotA and MotB rings of the stator created channel for protons to pass through and generate torque.
What two rings is the Rotor made of? What do they do?
S and M rings
Moving part of the motor structure
What family of genes makes up the larges part of the motor structure system, the filament?
The FliC genes, takes 20,000 FliC units.
What secretion system is important in the assembly of the flagellar motor structure?
What part of the structure forms this secretion system and how does is work?
The type III secretion system. (Where proteins are secreted out a ‘needle’)
The basal body forms a specialised version.
The hollow filament forms the needle, with flagellin subunits (FliC monomoers) transported through the it. The subunits aggregate at the tip, example of self-assembly.
Filament grows at the tip not the base.
What effect does cAMP-CRP activation complex have on genes for flagellum expression?
Positively enhances the flhCD operon.
What does expression of flhC and flhD genes form?
Create trasncriptional activation complex that activates the expression of ‘middle genes’.