1. Biology lecture 1 The E.coli Cell Gene expression Feedback And Control
Quorum Sensing
Taxis
Global Control
Enzyme Regulation

2. The E.coli Cell Cell Wall Cytoplasm
No ER or Golgi therefore most mammalian proteins cannot be expressed by Bacteria due to lack of post translational modification
DNA

3. Cell Wall Structure Phospholipid Bi-layer (Plasma Membrane)
Peptidoglycan
Phospholipid

4. The Cell wall in gram negative bacteria (like E.coli)
Passive Transport Protein
Outside
Has no access to proton gradient or ATP
Has proton Gradient and access to ATP
Active Transport Protein
Inside

5. Plasmids Present in nature Exchanged by competent bacteria
Encode genes
DNA

6. Gene Control Transcriptional regulation Translational Control
Protein Stability
DNA
mRNA
Protein
mRNA stability Control
DNA structural Control
Activation eg. Phosphorolation
Functional Protein

7. A Gene and Controll P R P O A B C R R I R I +

8. Ara BAD Operon + C PC P O I B A D P2 P1 Operator Promoters Inducer
Arabinose

9. Transcription Initiation
Polymerase
Inducer
DNA
This is Very Complicated we hide this complexity in a black box but it can affect the performance of our devices so you should know that it exists

10. Any form of gene control you can imagine
Multiple RBS
Multiple Promoters
Multiple inhibitors
Feedback loops, ie inhibitor under the control of it’s promoter

11. Two Component Systems External Signal Binds DNA
Membrane Bound Component (sensor) P P
ATP
Binds DNA P
ADP P
Intracellular Component (Transcriptional Regulator)

12. Quorum Sensing Allows Cell-Cell communication
Shows a Threshold Response
Lux R
Lux Genes
Lux I + -

13. Taxis Bacteria can move towards an attractant or away from a repellent
Attractants include
Chemicals
Light
Magnetism
Take Multiple readings using an analogue system
Remember previous readings
Move by a biased Random Walk

14. Global Control Stimuli
Effects are massive 150+ genes activated / inhibited per stimulus
Most operators / inhibitors are affected by a global control mechanism
Eg. Presence of Glucose is a stimulus for a global control mechanism so if a bacteria is grown on a glucose medium the araBAD operon will not initiate transcription.

15. Enzyme Regulation C B A E1 E2
Inhibition
Activation
No DNA, no translation, no transcription therefore very fast
Very hard to engineer and much less flexible than the systems mentioned earlier
Usually involved in central pathways therefore interference is likely

16. Any Questions?