Module 5: Salt Tolerance

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

Description

A core module for our project enables E.coli to survive the salt concentration of the ocean - without this ability the application of E. Coli to a marine environment would not be possible. This system would not be required for the other bacteria strains we will be transforming, Roseobacter denitrificans and Oceanibulbus indolifex, which as native marine bacteria already have genes conferring salt tolerance. Due to the widespread use of E.coli as a chassis for synthetic biology, this module is being developed to demonstrate that E.coli could be applied to marine environments.

The protein IrrE originates from Deinococcus radiodurans, where it confers resistance to radiation. When transformed into E.coli however, it protected against salt, oxidative and thermal shock. IrrE appears to function as a global regulator of stress factor genes. So far it has been demonstrated to upregulate transcription of recA and pprA – genes which encode Recombinase A and Radiation Inducible Protein. With respect to salt tolerance, IrrE upregulates the production of several stress responsive proteins, protein kinases, metabolic proteins, and detoxification proteins. It also downregulates glycerol degradation. With this global regulatory effect, E.Coli becomes more salt tolerant.

We propose to confer salt tolerance on E.coli by linking the salt tolerance gene encoding the protein IrrE (BBa_K729001) to a constitutive promoter (BBa_J23119). The choice of a constitutive promoter is intuitive; E.coli must sustain expression of salt tolerant proteins in order to survive.