Bio 1- L5- Motility and Chemotaxis in bacteria

how do bacteria respond to their environment?

• responses of gene expresssion

• responses at cellular structures

• physical responses to pH

• chemical responses to nutrients, signalling molecules

types of bacterial motility

• flgaellar

• gliding- using slime

• twitching- propelled by extension and retracting of TYPE IV pills

positioning on cells species specific- flagella examples- give on bacterial example

• monotrichous- 1 flagella on the end

• lophotrichous- multiple on the end

• amphitrichous- 2 flagella on either end

• petrichous- multiple flagella all over- e.coli

components of flagellar motor

1. filament- 20 microns

2. hook

3. basal body

4. p ring- periplasm

5. L and P ring- outside membrane

6. C ring- interacts with regulatory proteins

filament in flagella motor structure

• protein FLAGELIN- helical chains

• constant width

• synthesis- flagellin proteins move through hollow core

hook- flagellar structure(yellow)

• flexible

• wider than filament

• connects filament to basal body

basal body- pink- mention what bacteria type has a different type

• rotary- uses proton motive force

• positive- have 1 pairs of rings, negative has 2 pairs

• positive doesn’t have L and P rings

• rotor- MS rings

• stator- motA and motB

basal body in ecoli- how does it function

• rotor rotates- MS ring FliF- inner

• C ring- FliGMN- cytoplasm

• stator- proton powered

• MotA and mOTb- powers rotor

• protons bind to conserved aspartic acid in MotB- changes motA

chemotaxis- how does bacteria control direction?

• direction/frequency of flagellar rotation controls this

  • depends on flagella location

peritrichous flagella- how does it change direction and what is it?

• moves counterclockwise- forms a bundle and propels in straight runs

• run lasts 1 second

• movement stops when some flagella rotate clockwise- disengages from bundle and causes tumbling

• after tumble- direction is random

chemotaxis- difference is environment is favourable or not

• more runs than tumble if attractive- towards chemoattraction

• can’t go fully straight due to Brownian motion- small particles will deviate form straight line

chemotaxis in bacteria- how do cells detect and respond to cues?

• 2 component signalling systems

• sensor- histamine kinase system CheA and response regulator- altered expression of genes

1. sensing of Che system

• MCP receptors make a complex with CheA kinase and CheW

• ligand repellant binds- MCP forms dimer- and recruits CheW and CheA

• cheA- autophosphorylates histidine-48 residue

how does salmonella evade immune?

• capsule type- turns on and off genes

• changes between FliC with FljB- phase variation

2. response of the 2 component signalling systems

• CheA- transfers the phosphorylated to CheY

• CheY and P form a complex with C rings and FliMGN

• FliMGN tells basal body to switc direction- aspartic acid

Che system- what is it? how does it work?

• a two component signalling system

• ligand binds to MCP- recruites CheA and CheW

• CheA autophosphorylates histidine 48 and passes this to CheY

• CheY forms a complex with FliM and FliMGN C ring

• tells the basal body to switch direction