Synthetic Biology works A Montagud E Navarro P Fernández de Córdoba JF Urchueguía presents | Toggle switch | Repressilator | Counting machine z ETH iGEM 2005 | Memory device z ETH iGEM 2007 | Cell free system z Imperial iGEM 2007 | Synthetic pattern formation | Artificial Quorum Sensing | Artemisinin production
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Synthetic Biology works
A MontagudE Navarro
P Fernández de CórdobaJF Urchueguía
presents
Toggle switch
Repressilator
Counting machineETH iGEM 2005
Memory deviceETH iGEM 2007
Cell free systemImperial iGEM 2007
Synthetic pattern formation
Artificial Quorum Sensing
Artemisininproduction
Toggle switch
Toggle switch
Toggle switch
Toggle switch
Toggle switch
Toggle switch
● pTAK117● pTAK102
–– steady states–– unsteady state
Repressilator
Repressilator
Repressilator
n = 2.1 α0 = 0
n = 2 α0 = 0
n = 2 α0/α = 10‐3
Repressilator
Repressilator
siblings behaviour
phase amplitude period
Counting machine
ETHZ iGEM 2005
Counting machine
The counter is a finite state machine implemented as a genetic circuit. It has 4 internal states R1 to R4. The transitionbetween these states is induced by an external stimulus withvalues 0 and 1 ‐ denoting whether it is absent or present, respectively. Repeated stimulus will lead to successivetransitions and finally to repeated cycling through those 4 states. Each time the state R4 is reached, an output signal is
generated. This leads to a counting behavior where everysecond occurence of 1 (high signal) is indicated by the output signal.
Biologically, a NOR gate can be implementedthrough a promoter with high basal activity that isrepressed by three effectors. If there is at least oneof the three repressors, transcription is inhibited.
Fig. 1: Flow diagram. This figure shows the protocol with which the final systemshould be tested as well as the test results in form of the reported colors. Theprotocol is divided into three phases: (1) a training or learning phase in whichthe system learns an input and stores it in its memory, (2) a memory phase in which the system keeps the content of its memory, and finally (3) a recognitionphase where the output of the system depends on the content of its memoryas well as the current input.
Batch‐mode CFStranscription‐translation in bulk solutionexpression limited by nutrients & energy
Continuous‐exchange CFStranscription‐translation in dialysis membrane
expression sustained by diffusion of nutrientswastes diluted in feeding solution
Vesicule encapsulated CFSphospholipid bilayer separates from solution
maintained for a longer time period because of membrane diffusionnon‐specific pore protein increases reliability of material exchange
Cell‐free system
Expression system can be quality‐controlled by manipulating adjustable parameters e.g. buffers are addedto maintain optimummagnesium concentrations forefficient translation; protease inhibitors can be added tominimize degradation of synthesized proteins
No self‐replication of your genetically engineered deviceleads to a fixed amount of DNA being expressed andmore control over the rate of expression
No selective pressure on your genetically engineered devicebecause the system is non‐living and does not undergonatural selection
No DNA mutation of your genetically engineered devicebecause there is no DNA replication
Less characterization and experience of use in thelaboratories compared to E. coli
No concurrent expression of existing genome, thereforeyour genetically engineered device ismore energy efficient
Expensive system has no sustained metabolism to convertcheap energy (like sugars) into useable one for the gene expression machinery
Process is quick and simple requiring only preparation ofcell extract and feeding solution and subsequent addition ofDNA template
Short expression lifespan because of limited energy of thesystem even in the presence of an ATP regenerating system
System is not restricted by the policies imposed ongenetically modified organisms
DisadvantagesAdvantages
Cell‐free system
pink line : – control homemade E. coli S30 extract + homemade premix no DNAblue line : homemade E. coli S30 extract + homemade premix + DNAyellow line : commercial E. coli S30 extract + commercial premix + DNAblack line : homemade E. coli S30 extract + commercial premix + DNAgreen line : + control GFP protein in solution
homemadeE. coli CFS
Cell‐free system
dark blue line : 8ºCpink line : 15ºCyellow line : 20ºCblue line : 30ºC
commercialE. coli CFS
Synthetic pattern formation
Synthetic pattern formation
Synthetic pattern formation
Synthetic pattern formation
Synthetic pattern formation
Synthetic pattern formation
Synthetic pattern formation
Artificial Quorum Sensing
Artificial Quorum Sensing
Integrateintercellular comunication : quorum sensingcellular metabolism : acetate
transcriptional regulation : GFP
Tunable circuit
Artificial Quorum Sensing
pH(int) = 7.6
pH(ext) = 5 ‐ 8
ΔpH =
pH(int) – pH(ext)
Artificial Quorum Sensing
system after 10 hours
1/Kl
Artificial Quorum Sensing
in anaerobicconditions, E. coliproduces moreacetate
without pta, extracel∙lular [acetate] is notafected by oxygencondition
Artificial Quorum Sensing
Artificial Quorum Sensing
Artificial Quorum Sensing
pH promoter
tuning parameters
Artificial Quorum Sensing
pH(int) – pH(ext)
system after 10 hours
1/Kl
Conclusions
System works as a ‘quorum sensor’acetate, signal molecule, produced constantly
signal diffuses membrane
[acetate] relates to cell density
GFP expression only when a threshold is reached
Mathematical model predicts acurately the system’s behaviour
Artemisinin production
Artemisinin production
Anophelesmosquito with Plasmodium falciparumparasite causes malaria
Artemisinin from Artemisina annua is highly effectiveagainst multi‐drug‐resistant Plasmodium
short supply
expensive
Total chemical synthesis is difficult and expensive
Artemisinin production
Saccharomyces cerevisae
semi‐synthesis to artemisinicacid
Goals
Saccharomyces cerevisae
semi‐synthesis to artemisinicacid
mevalonate pathway
Saccharomyces cerevisae
semi‐synthesis to artemisinicacid
mevalonate pathway
A. annua:amorphadiene synthase
novel cytochrome P450 monooxygenase
Saccharomyces cerevisae
semi‐synthesis to artemisinicacid
mevalonate pathway
A. annua:amorphadiene synthase
novel cytochrome P450 monooxygenase
Overall metabolic tuningoverexpressionsinhibition
Artemisinin production
1. Adjusting the mevalonate pathway
2. From amorphadiene to artemisinic acid
3. Artemisinic acid analysis
1‐ Adjusting the mevalonatepathway
increase farnesil pyrophosphate(FPP) production
decrease sterols generation
ADS from A. annua
measuring [amorphadiene] by strains
ADS with GAL1 promoter
[amorphadiene] by strains
ADS with GAL1 promoter
upregulated: tHMGR
[amorphadiene] by strains
5x
ADS with GAL1 promoter
↑: tHMGR, upc2‐1 (↓sterol TF)
[amorphadiene] by strains
[amorphadiene] by strains
ADS with GAL1 promoter
↑ : tHMGR
↓ : erg910x
[amorphadiene] by strains
ADS with GAL1 promoter
↑ : tHMGR, upc2‐1
↓ : erg9
20x
ADS with GAL1 promoter
↑ : upc2‐1
↓ : erg9
2 x tHMGR
[amorphadiene] by strains30x
[amorphadiene] by strains
pGAL1‐ADS
↑ : upc2‐1
↓ : erg9
2 x tHMGR
↑ : erg20
pGAL1‐ADS
↑ : upc2‐1
↓ : erg9
2 x tHMGR
what enzyme?previous clues for a A. annuacytochrome P450
which one? comparativegenomics
Asteraceae family would sharecommon ancestors enzymesfor the early steps of thesesquiterpene lactonessynthesis
> 96 % of the synthetised artemisinic acid was removed from the cell pellet by washing with alkaline buffertherefore, artemisinic acid is transported out of the cell, but remains bound to cell surface on acidic medium
a one‐step purification method was developed:1) ether extraction of the culture medium2) silica gel column chromatographic separation
in vitro enzymeassays
microsomes
1
2
3
+ amorphadiene
+ artemisinic alcohol (1)
+ artemisinicaldehyde (2)
CYP71AV1 activities
Scientifical conclusions
Transgenic yeast effectively produces artemisinic acidArtemisinic acid is produced at a biomassfraction comparable to that produced by A. annua but over a much shorter time (4‐5 days vs. several months)
100x specific productivity for yeast vs. A. annua
Medical conclusions
Given the existence of known, relatively highyielding chemistry for the conversion of artemisinicacid to artemisinin microbially produced artemisinicacid is a viable source of this potent family ofantimalarial drugsA conservative analysis suggests that artemisinincombination therapies could be offered significantlybelow their current pricesIn addition to cost savings, this bioprocess shouldnot be subject to factors like weather or politicalclimates that may affect plant cultivation
sources
Gardner et al, Construction of a genetic toggle switch in Escherichia coli. Nature. 2000
Elowitz & Leibler, A synthetic oscillatory network of transcriptional regulators. Nature. 2000