Bacterial cell biology 3

Types of flagella movement

• Peritchilus flagellation →

  • Anti clockwise - > run , coherent movement / force

  • Clockwise → tumble, no coherent movement

• Polar flagellation → 1 falgella, Anticlockwise and clockwise both go sertain direction, can stop and then change direction of movement

In gram - what powers flagella movement

L P and MS rings

In gram + what powers flagella movement

the MS ring

what does the ring proteins do

• rings rotate causing Mot proteins to drive rotation of motor

Mot poretins are refered to as

stator proteins

The inner rings are known as

Rota proteins

what is the c ring

cytoplasm

How it all works

• ions pass through special channel membrane

• this creates electrostatic charge at rota

• rota located in C + MS ring interacts with these charges

• Mot proteins direct ion flow generating force for rotation

• Opposite charges attract and repel causing continuous spinning

Flagella synthesis

• about 50 genes involved

• the rings are added

• then the hook is added

• falagelin molecules then added from inside and move out

• part that comes out of cell is called flagellum

Other types of motility

Gliding motility

• Done by cells with no flagella

• movement on solid surfaces - use slime layers to move

Twitching motility

• done by type 4 pilus

• glide proteins which are attached to the surface which can move and pull cell along

Taxis

• movement to certain environment of away form unfavorable environment

If there is no gradient

cell tumbles a lot and runs to try find a gradient

If there is a gradient

• cell switches to running alot less rumbing in direction of gradeint

• the stringer the gardient the longer teh run

In big cells how do they sence a gradient

• scene a gradient on each pole of cell, what ever side is stronger move in that direction

• only done by big cells

how to sence in prokaryotic cells

• seance gradient at one time point then at another see if stronger or not

•    Cells respond to temporal differences rather than spatial differences

different types of taxis

-          Aerotaxis: movement towards or away from oxygen

-          Osmotaxis: movement towards or away from ionic strength

-          Hydrotaxis: movement towards or away from water

Two component system

• have a sensor kinase which repsondinss to signal form outside and phosphylates itself

• transfers phosphat to response regulator

• which then binds to DNA to turn off or on genes

Narx/NarL

• 2 different component systems that intercat together

• respond to signals and express GFP

• use bacteria as a sensor

• -          This biosensor detects nitrogen and nitriles, nitric oxide a all markers for inflammation

How cells move towards gardient

• MCP is a type of sensor kinase

• Once attractant bind causes CherY to phophylate itself and bind to flagella motor causing rotation

Quorum sensing

• when bacteria sence own denisty

• Bacteria release AHL moleucels

• f only a few bacteria are present, AHL levels stay low, and not much happens.

• If there are a lot of bacteria lots of AHL molecules and so start to move back inot bacteria triggers changes in gene expression

• So depending if how much AHL present that bacteria can decide how to act

• Different types of AHL allow species-specific communication

Engineered quorum sensing

• was importnat in ttaeting cholera

• Cholera is happing in populated enviroenmnt

• when not produces autoinduces (AL-2 CAI-1 )

• made a probiotic E.coli nestle ticked cholera thinking what in ahighly populated envirnment

• so sotpped inflamation

the 2 ways of understnding micorbrial comunites

• sequence 16s rRNA

• Shotgun sequencing

Human gut micorbiome

·       Stomach: 10⁴ microbial cells per gram (pH 2)

·        Small intestine: 10⁸ microbial cells per gram (pH 5)

·       Colon: 10¹¹ microbial cells per gram (pH 7)

what does the bacteria in the colon do

• Fermentation of complex carbs (fibers)

• Produces vitamins that body cannot make e.g. thymine, Folate,,