Module 5: Salt Tolerance

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

Description

A core module for our project is enabling E.coli to tolerate the salt content of the ocean; without this ability E.coli could not survive in a marine environment. This system is not required for other bacteria we will be transforming, Roseobacter denitrificans and Oceanibulbus indolifex, which as native marine bacteria already have salt tolerance. Rather, because of the widespread use of E.coli as a chassis for Synthetic Biology this Module is being developed to demonstrate that E.coli too could have the capacity to carry the plastic formation or degradation system.

We propose to confer salt tolerance on E.coli by linking the salt tolerance gene encoding the protein irrE BBa_K729001 to the 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.

The protein irrE is found naturally in 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 work by regulation of a number of genes. So far it has been demonstrated to upregulate transcription of recA and pprA – genes which encode Recombinase A and Radiation Inducible Protein. This may be involved in promoting DNA repair and protecting against oxidative damage when transformed into bacteria, but the exact mechanism of salt tolerance is not clear. We will specifically investigate the ability of irrE to confer salinity tolerance in E. coli, as previously demonstrated by Pan et al. 2009.