Team:Grenoble/Biology/Network

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<li><b>[13]</b> <a href="http://ecocyc.org/ECOLI/NEW-IMAGE?type=OPERON&object=TU00214" target="_blank">Transcription Unit: araBAD</a></li>
<li><b>[13]</b> <a href="http://ecocyc.org/ECOLI/NEW-IMAGE?type=OPERON&object=TU00214" target="_blank">Transcription Unit: araBAD</a></li>
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<li><b>[14]</b> <a href="http://www.ncbi.nlm.nih.gov/pubmed/18414488" target="_blank">alagaddé F. K., Song H., Ozaki J., Collins C. H., Barnet M., Arnold F. H., Quake S. R., You L. (2008). A synthetic Escherichia coli predator-prey ecosystem. <i>Molecular Systems Biology</i>. 4:187.</a></li>
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<li><b>[14]</b> <a href="http://www.ncbi.nlm.nih.gov/pubmed/18414488" target="_blank">Balagaddé F. K., Song H., Ozaki J., Collins C. H., Barnet M., Arnold F. H., Quake S. R., You L. (2008). A synthetic Escherichia coli predator-prey ecosystem. <i>Molecular Systems Biology</i>. 4:187.</a></li>
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Revision as of 23:07, 24 September 2012

iGEM Grenoble 2012

iGEM Grenoble iGEM
iGEM 2012
main page
Project

Network details

Our system is divided in two modules:
  • signaling module
  • amplification module

Signaling module

The signaling module allows our bacterial strain to integrate the input signal = the pathogene presence.

This is also one of our module of modeling.

The idea of this module is du to the iGEM London Imperial College 2010 Team work on Parasight [1].

Staphylococcus aureus secretes an enzyme, exfoliative toxin B [2] which cut a specific amino-acids sequence (Desmoglein 1). This specific sequence can be used as a linker between a membrane protein and a dipeptide.
Once S. aureus is present, the linker is cut by the protease and the dipeptide is released.

The dipeptide binds to his receptor which is an engineered [3] [4] receptor:
  • the extracellular part is the extracellular part of Tap [5], a dipeptide receptor involved in the chemotaxism
  • the intracellular part is the intracellular part of EnvZ [6], a histidine kinase involved in the osmoregulation

Once the dipeptide is bound to the Tap part [7], the EnvZ part allows the phosphorylation of OmpR [8] [9], a transcriptional activator which is constitutively produced.

Once OmpR is phosphorylated, it allows the production of adenyl cyclase by activating the OmpC promoter [10]

Amplification module

The amplification module allows our bacterial strain to amplify the input signal and to produce an output signal = fluorescence.

This is also one of our module of modeling.

Internal amplification


Adenyl cyclase [11] is an enzyme which catalyse the conversion of ATP (Adenosine Tri-Phosphate) to cAMP (cyclic Adenosine Mono-Phosphate).


cAMP binds to CRP (C-reactive protein) and then this complex allows the production of AraC by activating the pMalT promoter [12].
In the presence of arabinose, AraC, with cAMP-CRP, activates the pAraBAD promoter [13], forming thus an "AND" gate, which allow the production of:
  • adenyl cyclase which reproduce cAMP, forming thus an amplification loop
  • GFP (Green Fluorescent Protein) = our output signal

External amplification

When one bacterium detecte S. aureus, it produces a lot of GFP and cAMP. cAMP can diffuse through the membrane and activates the amplification loop in all the neighbourings bacteria [14] which can thus produce a lot of GFP and cAMP.
The result is an entire population which produce GFP whereas only one bacterium has detected the pathogen in the first place:


References

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