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Module 3 - Killing Strategy


  • As our bacteria are to be ingested, we wish to destroy all genetic material to prevent any pathogenic response to the patient. A number of different mechanisms exist to program cell death, and destruction of genetic material.

N.B. less so for pathogenic response, to prevent horizontal gene transfer between bacteria within gut. E-coli non-pathogenic as is, but do not want mutatable viable bacteria present. Also for public acceptance - swallowing live versus dead bacteria.

  • Should be designed as to trigger after encapsulation is complete. Depends on encapsulation technique and application.
  • Need to define the amount of time taken for bacterial genetic information to be removed (instantly destroy genetics of whole population or a slower trailing process, ideally all at once)
  • We ideally would like a failsafe mechanism to trigger cell death if the main mechanism should fail or be evolved out. This double mechanism will that no bacteria will survive once the cell death program has been triggered.
  • Effectiveness of each method should be assessed, so the probability of any bacteria surviving can be calculated.
  • Programmable cell death is an idea used in previous iGEM teams, some notable examples have been put up and summarised for ideas.

Key Aspects


We hope to use any combination of restriction enzymes and ccdB to destroy the genetic material in our chassis. We are also researching into recombinases as another possibility - Xer and Dif sites will recombine in the presence of the required enzyme, and excise the genes between them. If we target this around an important gene in our bacteria we could use this as another method of removing the genetic material.

Restriction enzymes depend on the chassis used. There are several possibilities for both B-subtillis and e-coli.

Interesting Papers

| Programmed Cell Death in Prokaryotes
Summary of different ways of triggering cell death

  • James Chappell 03:43, 21 July 2009 (EDT):would be interesting to review this or similar papers to see the natural ways that E.coli cells are targeting death and see if we can engineer some of these mechanisms