The cells that were transformed to contain Dsup were found to have significantly higher survival rates than those without Dsup. Overall, cells containing Dsup--both induced and uninduced--showed an average survival rate of approximately 26% after four hours of exposure to UV-B radiation, while the cells containing only blue chromoprotein (without any radiation resistance genes) showed a survival rate of 0% after four hours. The most pronounced difference between cells containing Dsup and cells containing no radiation resistance was found at three hours, with Dsup-containing cells having an average survival rate of 49% and non-Dsup-containing cells having an average survival rate of 2.3%, meaning that cells with Dsup survived at a rate that was, on average, 2130% higher than the rate at which non-Dsup cells survived.
There was no significant difference observed in the survival rates of cells in which expression of Dsup was induced via addition of IPTG and cells in which it was not induced, indicating extremely leaky expression in the Lac promoter.
Failed Expression and mRNA Secondary Structures
Although the constructs were successfully transformed into E. coli and showed expression of blue chromoprotein, our reporter, we were not able to obtain any conclusive data on the radiation resistance capabilities of phrAc, phrAt, and uvsE.
A protein expression test was performed on uvsE + blue chromoprotein (BCP), phrAc + BCP, and phrAt + BCP in order to determine the cause of the failures of our trials. The expression test showed expression of BCP in the constructs containing uvsE and phrAc but no expression of the radiation resistance genes themselves, indicating that it is likely that the mRNA was successfully transcribed but problems occurred during translation of the radiation resistance genes. In the construct containing phrAt, there did appear to be expression of the phrAt gene, but no radiation resistance was observed.
The failure of uvsE, phrAc, and phrAt to provide any radiation resistance can likely be attributed to the strong secondary structures present in the radiation resistance portions of these constructs and minimal secondary structures present in the BCP portion of the constructs. This is consistent with the observation that blue colonies were present on the plates on which these cells were grown, but no radiation resistance was observed.