Final System

Our B. s. detector addresses the global problem of malaria misdiagnosis. It is a DNA-based detection tool using Bacillus subtilis as a chassis, taking advantage of innate homologous recombination mechanisms. The bacteria exists in spore form, simply hydrated for activation. This feature will eliminate the need for refrigeration both during transport and long-term storage. Given its robust nature, our device should have the ability to function in even the modestly equipped clinics and laboratories.

A small blood sample obtained from the patient is amplified using isothermal PCR, circumventing the need for hefty machinery to carry out thermocycling. This process is supplemented with a specialized Taq polymerase that is able to function well in the presence of blood.The amplified product then travels to chambers containing B. subtilis engineered with pathogen-specific complementary flanking regions around the repressor in our genetic circuit. Thus, when B. subtilis is transformed with the product (via xylose induction) and target DNA is present, the flanking regions switch out the repressor. When the repression is lifted, the reporter becomes active. This results in a colour output.

Thus, a colour output is given when the target DNA is present to cause de-repression of the reporter circuit.

Figure 1: A 3D model of our final system: three secondary chambers are attached to the central chamber at 120° for equal fluid flow. Combining aspects of isothermal PCR, bacterial sporulation, and a simple binary colorimetric output, our device offers a multiplexed, low-cost diagnostic solution capable of functioning anywhere in the world.