Part:BBa_K3973002:Design
Quorum Sensing Kill Circuit
- 10COMPATIBLE WITH RFC[10]
- 12INCOMPATIBLE WITH RFC[12]Illegal NheI site found at 144
Illegal NheI site found at 167
Illegal NheI site found at 2643
Illegal NheI site found at 2666 - 21INCOMPATIBLE WITH RFC[21]Illegal BamHI site found at 946
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000COMPATIBLE WITH RFC[1000]
Design Notes
The 2021 Hopkins iGEM team constructed a circuit that operates on a similar principle, such that the constant application of 3OC6HSL, as accomplished through quorum sensing and production by esaI, is necessary to keep cells in a survival state. The team also included weak constitutive expression of the antitoxin mazE to combat leaky expression of mazF within survival state cells and to limit the potential burden of the circuit. MazF toxin was selected because of its known effectiveness and because it does not cause cell lysis (which could lead to the dispersal of plasmid and chromosomal DNA).
Quorum sensing is accomplished via the Erwinia stewartii esaI/esaR quorum sensing system. Constitutive esaI production increases 3OC6HSL concentration, which drives TetR production through derepression of the esaR promoter. Production of TetR directly inhibits toxin production, and low constitutive mazE expression neutralizes leakily expressed mazF.
If 3OC6HSL is low (i.e., low population), the production of TetR is limited. The pTetR promoter is active and production of esaR increases, causing rapid transition to the default death state and toxin overexpression.
Source
A majority of this circuit relies upon one constructed by Chan et al. in their 2015 manuscript 'Deadman' and 'Passcode' microbial kill switches for bacterial containment. The authors discussed the development of a monostable genetic switch that required the constant application of an external signaling molecule for cell survival and otherwise defaulted to cell death.