Module 4: Buoyancy

Description | Design | Construction | Characterisation | Modelling | Results | Conclusions

Modelling

We have two separate models for buoyancy, namely a Simbiology Model and a MATLab Mathematical Model. The aim for the simbiology model was to investigate if the addition of T7 RNA Polymerase as well as T7 promoter woud increase the expression levels for the GFP.

Simbiology Model

The block diagram shows the module where GFP expression is control by cstA promoter; the expression is triggered under low glucose concentrations.

In the models the environmental sensitive promoters (cstA) is activated by carbon starvation stress, then the mRNA encoding T7 RNA polymerase is transcribed, whose protein binds the T7 promoter driving the expression of the the reporter output (GFP).

Graph represents the GFP accummulation through time when is controlled by cstA promoter

The green line represents GFP expression levels and the blue line shows the T7 RNAP concentration over time. GFP production is considerably higher than in the previous model.

Mathematical Model

Given a fixed ratio of volume of gas produced to total e.coli volume, this model calculates the number of e.coli cells required to keep a certain mass of aggregated microplastic buoyant. The model also compares how the number of cells is affected by varying densities of microplastics, and allows the user to investigate how the results will change in different sea water densities. Sea water density, under influence of temperature, salinity and pressure, can be calculated using a third party [http://www.csgnetwork.com/water_density_calculator.html calculator by CSG Network].

Taking sea water density to be at 1020kg/m3, and volume ratio of gas produced in e.coli to be 0.5, the model produces the following graph.

Conclusion and influence to our experimental work From the results obtained above we can see that our model suggest increase of expression of GFP when the T7 RNA Polymerase as well as T7 promoter are added to the original construct (which was cstA + GFP). We expect that our experimental data fill follow this.