Because thiosulfate and tetrathionate are indicators of intestinal inflammation (Levitt et al, 1999), this system can be used to detect it noninvasively. Although the detailed process and reasons for their production are still unknown, it has been established that the level of thiosulfate and tetrathionate is directly proportional to the seriousness of intestinal inflammation. Until now, scientists were able to detect thiosulfate and tetrathionate using a detector based on a two-component system, which includes two parts: detector and reporter. The detector was derived from a marine Shewanella species, and previous experiments on the detection of intestinal inflammation used sfGFP to show the result. However, we thought this method can be further improved.
The SHSBNU_China team worked on changing the reporter part to display the results more clearly and visibly, not requiring specially-produced ultraviolet light or prolonged contact with oxygen. In our system, E. coli would produce a chromo-protein to change its color (even in an anaerobic environment). Furthermore, to enable the result to be observed more easily and to ensure its safety, we planned to produce a pill in which the modified E. coli is stored, with special walls that would only allow small molecules to pass through. In addition to the conventional chromo-proteins it can produce, we designed and produced an additional plasmid using violacein as the reporter. Violacein was successfully produced and the corresponding strain showed obvious purple color under anaerobic conditions. The special reason for choosing violacein is that this compound can cure or at least slow down the inflammation to some degree.
The two-component system detector used in our project has the potential to be further modified to produce additional treatments upon detecting inflammation. We also came up with solutions to reduce potential risks in practical treatments. For example, we have discussed creating kill switches, using DNase to destroy the engineered gene to prevent its spread into the normal gut flora.