M2 Genetic Circuit

Video

A short video presentation has been prepared to explain the genetic circuit of Module 2 in detail.

Genetic circuit

The genetic circuit for Module 2 consists of two parts. The first part contains the genes involved in encapsulation and colanic acid production, while the second part contains those genes required for the production of trehalose.

Module 2 is initiated upon the cell switching to the secondary carbon source. For this reason, both parts of the module are under the control of the same glucose sensitive promoter - PcstA.

Elaboration

Genes RcsB, YgiV and Rfal control the production of colanic acid. RcsB is concerned with generating colanic acid, YgiV increases the yield and Rfal attaches the colanic acid produced, to the outer membrane of E. coli.

Genes OtsA and OtsB are involved in the production of trehalose.

Encapsulation is induced automatically when the concentration of glucose decreases below threshold. Initially, glucose concentration is high and this represses the CRP promoter. No transcription occurs and encapsulation does not occur. As E. coli grows, it consumes glucose, resulting in a decrease in glucose concentration until the threshold is reached. At this point, glucose will no longer be able to repress the CRP promoter. Colanic acid and trehalose would be produced.