Module 5: Salt Tolerance

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

Conclusion

We have determined that IrrE is an ideal global regulatory gene to be utilised in conferring salt tolerance on our cells. Transforming our cells with the IrrE gene, we have successfully increase the growth rate of E. coli in high salinity conditions.

Within the greater boundaries of our project, this will allow survivability of our E. coli cells in the marine environment. As the ocean has a salinity of approximately 0.6M NaCl in the north pacific gyre, our cells will be able to effectively survive in those conditions. It should also be noted that direct comparison with a previously constructed salt tolerance BioBrick has shown that use of the UCL '12 part gives greatly elevated growth rates during the exponential growth phase, key in ensuring a sufficient population for acting on the microplastic targets.

We note that the global regulatory function of IrrE allows it to confer protection against several other abiotic stressses to E. coli, which we have not covered within the scope of our project. This can potentially be the scope of future investigation, determining the boundaries of environmental conditions that IrrE allows E. coli to withstand.

From the modelling system, where gene knock-outs were tested on wild-type and IrrE-modified bacteria in order to analyse the effect or IrrE on cell growth rate in higher salt-levels, it can be seen that in line with experimental observations, IrrE negative bacteria (wild-type) shows greater growth in comparison to IrrE positive bacterium. In the future we would like to investigate E. coli metabolic flux further and predict other effects of irrE to E. coli metabolism.

In the future, we would like to further investigate our IrrE BioBrick (BBa_K729001). While our project has only focused on the salt tolerance imbued by the IrrE gene, we have not fully explored the potential of the gene. Due to the global regulatory function of the IrrE gene, cells transformed with this BioBrick are likely to be highly environmentally resistant, and hence we would like to characterise the resistance of transformed cells to other abiotic stresses, such as UV radiation and nuclear irradiation.