Temporal Control

Engineering Approach to Temporal Control

This temporal control platform showcases our engineering approach in the E.ncapsulator project. We’ve made our entire system modular. Each module can essentially be pictured as a blackbox with one temporal control input and one output. Therefore, each module is linked to the next module by temporal control. Temporal control has allowed us to create a system that can be reused in other projects in synthetic biology. It is in fact a novel engineering approach that is both reusable and elegant.

In our temporal control system, we have employed 3 kinds of temporal control:

• Chemoinduction:

Production of the protein of interest is triggered by the addition of a chemical.

In our case, we have chosen IPTG. IPTG will be added when the cell density is deemed sufficient for protein production (Module 1) to begin.

• Autoinduction:

When glucose levels have fallen to nearly 0, encapsulation (Module 2) will begin automatically in response.

In our case, this will allow a sufficient amount of protein production to have taken place, before the cell focuses its resources on encapsulation.

• Thermoinduction:

Genome deletion is triggered by the increase of temperature. This is the last step of the temporal control system.

In our case, thermoinduction was necessary, as chemical induction may be blocked by the presence of the capsule (that inhibits diffusion).

Timeline of Temporal Control

Testing Construct

This testing construct was used to test the inducible promoters using flourescent proteins as output reporters.

Key to genetic circuit diagrams

This timeline shows the sequence of occurrence of these events:

  about the timeline and its explainations.

Our Results

Growth on 0.5% Glucose + Arabinose

From the positive rhanmose plot, we can observe diauxic growth, which is an initial exponential growth when glucose is consumed, followed by a stationary growth phase when glucose runs out. When the cells start consuming the secondary carbon source (Rhamnose in this case), an exponential growth is again observed.

  about the wetlab results!

The first of our diauxic growth models is a cybernetic model developed by Kompala et al [1]. This model shows that glucose (S1) is used up before the secondary carbon source (S2). During this phase, the population (X) is in exponential grow until glucose (S1) runs out. This is followed by a stationary growth phase, and finally the population enters a second exponential growth phase as they start uptaking the secondary carbon source (S2).

  about the models and simulations!

References

[1]Kompala, D.S., D. Ramkrishna and G.T. Tsao, "Cybernetic modeling of microbial growth on multiple substrates," Biotechnology and Bioengineering 26 :1272-1281 (1984).

Project Tour

For more details of the temporal control of the system, see the tabs below.

Temporal Control Contents