The system is dependent on the output of the filter, and has therefore got a T7 RNA polymerase promoter (BBa_I712074) followed by a RiboLock (BBa_J23078). The aiiA gene (BBa_C0060), short for autoinducer inactivation, is placed downstream of this AND-gate and codes for lactonase, an enzyme that hydrolyses the 3OC6HSL ester bonds. (reference)
This device was conceived to reset the Timer.
When significant input (re-)emerges, lactonase is produced. It will then convert all available intracellular 3OC6HSL at that time to a hydroxy-acid, thereby inactivating and efficiently removing it from the active system. This way, the timer is reset and the cell may live to see another day.
Originally, a device generating a pulse of lactonase was thought to do the job, but modeling suggested that the amount of lactonase produced during this pulse was too small to accomplish a thorough reset of our system. So the device was reinvented and a simplified (non-pulse) version was devised and described here. Now the amount of lactonase produced should be high enough for the reset to function properly.