B.s. Detector

The B.s. detector is a diagnostic tool designed to simultaneously identify the presence of several pathogens within a blood or fluid sample through the detection of specific sequences within genomic DNA. At the core of our device lies the gram positive - and eponymous - bacteria B. subtilis which has been genetically modified to harbour two specific operons (a cluster of genes intended to be activated together) of our own design working in tandem. The first operon (i.e., the reporter operon) consists of the lacZ gene along with an operator gene which is necessary for the function of lacZ.lacZ, when operational, is designed to produce a blue pigment (5,5'-dibromo-4,4'-dichloro-indigo) in the presence of the organic compound X-gal. The second operon (i.e., the repressor operon) consists of a repressor gene designed to inhibit the function of the first operon and prevent the blue pigment from being synthesized. The repressor gene is surrounded by two flanking sequences on the 5' and 3' ends which will play a crucial role in the diagnostic mechanism of our device. The flanking regions are designed to share a high level of homology with target sequences found within the genome of our pathogens of interest. These sequences will be identified beforehand using public genome data repositories. Upon contact with a pathogen, the flanking regions within our repressor operon will recognize the target sequence and undergo homologous recombination, a process in which nucleotide sequences of a certain size are exchanged between two similar (homologous) DNA molecules. Homologous recombination will result in the flanking regions - and the repressor gene sandwiched in between - "switching places" with the target sequence. With the repressor gene removed, the repressor operon will no longer be able to inhibit the report operon and blue pigment will consequently be produced. Essentially, the presence of a certain pathogen will be indicated by a easily identifiable colorimetric output.

In summary, our genetically engineered B. subtilis will by default be in a negative state and lack blue pigment due to the repression of the reporter operon by the repressor. However, upon contact with a target sequence, the repressor gene will be removed from the repressor operon through homologous recombination and the reporter operon will be free to produce the pigment. This simple negative (no colour) to positive (colour) transition is the basis of our diagnostic method.

3D Device Animation using Autodesk Maya (Click here if video isn't working)