From 2007.igem.org

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Self-differentiated Bacterial Assembly Line

Our projects concerns with the ability for bacterial cells to differentiate out of homogeneous conditions to achieve division of labor.

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 have adapted natural conjugation systems as the communication device, and the conjugative 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 are going to engineer the E. coli cell to behave as a push-on push-off switch. We have designed a gene regulatory circuit that senses Ultra-Violet light (UV) irradiation as input signal. Under intermittent irradiation, two reporter genes are to be induced alternately. The circuit can be divided into two associated parts: a bistable switch and a NOR gate. The NOR gate is controlled by the bistable switch and the input signal. On the other hand, the output of the NOR gate can switch the bistable state from one to the other. Thus far, we have constructed a series of NOR gates and one bistable switch.