Module 5: Salt Tolerance

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

Characterisation

IrrE is deduced to globally regulate gene expression in E.Coli, and to date, no specific assay allows for the convenient determination of IrrE expression (citation needed). As such, the expression of IrrE will be determined indirectly by determining the increased salt tolerance of our cells. In order to confirm this, we will be conducting growth curve experiments. This will allow us to determine if our cell grow to a higher density in high salinity when compared to the untransformed cells.

As we will be using Lyon 2010 iGEM team's K540000 salt tolerance BioBrick for comparison, we will also attempt to replicate their results via growth rate experiments.

Characterisation of BBa_K540000 for Comparison

We have observed that the results we have obtained for the characterisation of K398108 are consistent with those of the TU Delft '10 iGEM team. From the growth curves obtained (see graph below), an increase growth rate during the exponential phase is observed in E.Coli expressing BBa_K398108 as opposed to the wild type when the salt concentration of the media is elevated.

However, while we have managed to replicate the results of the TU Delft '10 iGEM team, we question the viability of this BioBrick for conferring salt tolerance in E.Coli. While the growth rate is improved for the cells expressing the BioBrick, the overall exponential growth phase does not - from our results, the final OD of the cells in the stationary phase is not higher than that of the wild-type.

Examining the literature, a better gauge of salt tolerance can be found via an increase in OD over the wild type cells in increased salt concentrations, which this BioBrick has not been shown to do. As such, the choice to use K398108 to confer salt tolerance on our cells would remain questionable at best.