IGEM:IMPERIAL/2009/Encapsulation/Timers
Timers
Timers have many biological and engineering appplications. Design of mechanisms and characterisation of parts will provide a reusable timer module.
We could have a timer module as part of Phases 1, 2, 3 or 5 of our project.
Previous iGEM teams have explored different genetic circuits required to produce a timer (See the links for more info on each).
Considerations for our timer:
- Separate timer for each phase vs. one timer that is ‘continuous’ between phases
- Thresholds
- Periodicity
- Start/stop vs. oscillation vs. combination of both
- Reset function
- Pre-programmed function(s)
KULeuven2008
KULeuven used the 'InverTimer' in their 'Dr. Coli' project to induce destruction of their bacteria once the time lapsing between disease signals had reached a sufficient period.
Their system is a LacI based inverter, controlling LuxI production. LuxI produces AHL (quorum-sensing molecule) which in turn gradually activats LuxR and its controlled promoter in the next module/device.
NYMU-Taipei2008
Taipei made two timers based on a three-component system:
Starter, Counter, Stopper
The counter component of the system is an oscillator. They required two timers with different periods so used different oscillators to fit the purpose of each timer.
Cyanoxilator
- A Cyanobacterial oscillator using the Kai proteins in E.coli.
- Time period of between 14 - 60 hours (...wide range there??)
Reloxilator
'A tuneable intracell-synchronized relaxation oscillator based on the combination of:
- Using the lysogenic genetic swtich from phage lambda and giving it tuneable oscillatory properties.
- Using the intracellular synchronising properties of Vibrio fischeri.
- Time period of ~46 minutes.
The timers are stopped once protein production reaches a pre-set threshold. Once this threshold is reached, the activity of the output promoter changes.
