Manchester-Graz Collaboration

The Manchester-Graz team have developed an expression system designed to regulate single and multi-gene pathways for an intestine expression. For controlling a wide range of pathways it is designed in a flexible and modular manner. They tested the production of butyrate in the gut. The pathway was incorporated into the expression system model to observe the expression of butyrate under the control of the developed system. The model generated helped us to understand how the system is dealing with pathways that consist of several enzymes at an intestinal level.

The system consists of two quorum sensing (QS) systems EsaR/I and CepR/I. The EsaR/I system belongs to the plant pathogen Pantoea stewartii . The second QS-System, CepR/I, belongs to the opportunistic pathogen Burkholderia cenocepacia . For details about the system and the model please look into the Manchester-Graz modelling page.

Butyrate is converted starting from two acetyl-CoAs over several steps to butyryl-CoA. In the last step, the coenzyme A is transferred to acetate, producing acetyl-CoA and butyrate₁. For simplicity, the pathway was reduced to some essential parts and steps in the pathway. Acetate is converted to acetyl-CoA. The steps to butyryl-CoA are reduced to one step. Coenzyme A is recycled in the last step to butyrate and can be reused to produce acetyl-CoA (Figure 1).

The pathway is controlled by three enzymes whose expression is controlled by the two quorum sensing systems.

If we simulate the model, in the first two minutes the acetate gets first converted into butyryl-CoA and then the butyrate production starts (see Figure 2). The following time is butyrate being produced constantly by the cells. The butyrate is transported out of the cells through diffusion by a rate of 207.6 µmol/h/L or 18 mg/h/L.

Figure 2: Butyrate production in the first two minutes.