IGEM:IMPERIAL/2009/EncapsulationP3 PastIdeas

Berkeley iGEM 2007 - Bactoblood Usable

• Self destruct to remove genetic information whilst leaving cell membrane intact.
• Uses a plasmid that can be translated to produce a toxin.
• Toxins are endonucleases/ RNAses, and induced using Pbad promoter

| Berkeley iGEM '07 - Bacterblood

Pros :

• Two biobricks for inducible toxins used - Barnase (RNAse) and BAMH1 (Restriction Enzyme)
• Does not destroy cell membrane, but destroys genetic material, and importantly, proteins still functional within cell membrane.
• Stops cell growth after toxins are induced.

Cons :

Variations

Small cutters, could cut the genome in little pieces

• E. Coli: inducible promoter + restriction enzyme
  
  • eg.: Hsp92II + Xylose inducible promoter (could be derived from http://partsregistry.org/wiki/index.php?title=Part:BBa_K100000)
• B. Subtilis: stress inducible promoter + restriction enzyme
  
  • eg.: EcoRI + σB inducible promoter
    

Large cutters, could cut the specific gene

• Eco571
  
  • this enzyme cuts the PAH gene (PKU application) into three parts, 37°C operation
    
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• AsuHPI
  
  • Tripple cutter for PAH sequence, 5nt recognition sequence, 37°C operation
    
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KU Leuven iGEM 2008 - Dr. Coli Usable?

• Programmable self destruct mechanism to destroy the helper bacteria when it is no longer needed.
• Uses CcdB as the toxic product, and expression is controlled by luxr gene.

| KU Leuven iGEM '08 - Dr. Coli
The ccdB gene seems to transcribe an inhibitor of DNA gyrase and also involves topoisomerase. Pros :

Cons :

• Complicated sequence involving leaky stop codons and several inhibition pathways

*We must use a non-leaky promoter otherwise it will kill the colony slowly.

| Minnesota iGEM 2008 - Project Timebomb Not usable

• Programming bacteria suicide after a certain number of cell divisions has been reached.
• Uses antitoxin-toxin gene pair MazEF
• MazF codes a stable lethal toxin, MazE codes a less stable anti-toxin, to nullify the effects of MazF. Inhibition of MazE production results in cell death through the toxic effects of MazF

Pros :

• | Research has shown that transcription and/or translation inhibited by several antibiotics results in inhibition of MazE expression, so resulting in cell death. Could potentially be used if external factors are used as trigger for cell death.

Cons :

• Suggests a threshold mechanism for cell viability. Above which genetic material removed, below which genetic material survives. Actual mechanism likely to be more complicated and not so 'black and white.'
• Biobricks not published.

* Secreting a toxin in our system is not a possible solution