From 2007.igem.org

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Hop Count with Conjugation

Hop counting is a cell-cell communication system in which the signals transfered among the cells record the number of times of transfer. We decided to use conjugation as our one to one cell-cell communication system and plasmids as the vector for the transfered signal. With the rolling-cycle replication of conjugation, independent tandem oriT (BBa_J01002 and more) pairs can be inserted into the same plasmids, losing one tandem region at each single conjugation event. Sequential conjugation and deletion of the different oriT pairs can be achieved by fine control of the expression of the cis-acting elements of the independent conjugation systems.Besides intellectual interests, these systems are the core parts of controllable and encoded local cell-cell communication, which can be used in potential pattern formation and material weaving applications.

Push-on-push-off Switch

We propose to construct a gene regulatory circuit in E. coli which functions as a push-on/push-off switch. The immediate output of such circuit is determined by the input signal and the internal state of the circuit. It is designed to response to low dose UV irradiation. Under intermittent irradiation, two reporter genes are expected to be induced alternately.