The team, led by assistant professor Mark Styczynski, engineered E. coli to sense and respond to zinc in blood samples. How did they turn E. coli into such a sophisticated bio-sensor? Lucky for them, the bacteria already produce a system that senses zinc. The next step was to link this sensor to pigment production. For this, they incorporated genes from other bacteria that produce lycopene (red pigment), beta-carotene (orange), and violacein (purple).
The idea is that healthcare personnel working in resource-poor areas can separate plasma from blood samples using a simple centrifuge. Then, they will add a freeze-dried pellet of bacteria to the plasma. After around 24 hours, the bacteria will produce enough pigment to be easily visible to the naked eye. Purple means there is too little zinc, while orange and red indicate normal and borderline levels, respectively. According to Styczynski, “the general idea of bio-sensing is certainly out there, but we have taken the step of developing a system that doesn’t require equipment in the field … we believe this will work well in low-resource areas”.
One drawback is that E. coli does not require the same micronutrients as humans. This means that other organisms, such as yeast, will have to be similarly engineered as bio-sensors. Regardless, this “bacterial litmus test” could no doubt revolutionize medical diagnostics for resource-poor communities.
Sources: Metabolic Engineering, Science Daily, CDC