Tokyo/Requirements

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Abstract　　Concept & Model　　Requirements　　Genetic_circuit　　Works　　About_our_team

The most important and underlying point of our model is that the system is stable against environmental changes when two or more types of individuals coexist, called "stable coexistence." Our project have aimed at this "stable coexistence" but not dynamic equilibrium such as chemical ones.

To achieve this “coexistence stability,” our model requires
1. bistability at two distinct states in a single cell
2. cell-cell communication by quarum sensing

Fig.1: Bistablity

1. Bistability

1-1. At an individual level

For "coexistence stability" in our model, two types of cells should coexist stably. Therefore, cells with THE SAME GENE SET need to take TWO STATE STATES, A (Worker) and B (Idler) in our project as shown in Fig. 1. To be clearly distinduished from dynamic stability, "coexistence stability" must be achieved by two distinct states unconvertible each other.
1-2. At a collective level
To achieve "coexistence stability," each cell needs to feel cell types - the ratio of A and B - around. As is often the case bacteria in the nature, our modified cells here sense the types of coexisting cells by cell-cell communication called quorum sensing. Under the coexistence of A and B at a specific ratio, the whole system (or group) is collectively stable. Fig. 2 simply shows this scheme.

2. Cell-cell communication

When this stable coexistence is disrupted, by removing all the A type for example, these individual cells sense the change. Their states A or B become unstable as if cells became upset - INDIVIDUAL STATES ARE UNSTABLE ⇒ They are COLLECTIVELY UNSTABLE. Then some of them changed their states while the others do not. As a result, at a certain ratio of A and B again, the whole system comes back to a stable states. Here the cells are COLLECTIVELY STABLE ⇒ INDIVIDUALS ARE STABLE under this stable coexistence.