Yeast can be used to make beer and bread, and now - medical diagnoses. Using only baker’s yeast, filter paper and a 3-D printed holder, researchers at Columbia University designed an inexpensive, on-the-spot test to detect major fungal pathogens.
Diagnosing fungal infections, which kill 2 million people each year and cost global agriculture more than $60 billion annually, is a complex, expensive procedure; but, synthetic biology researchers found a way to replace the specialized equipment with a simple, one-component biosensor that could cost less than a penny.
Writing in the journal Science Advances, Nili Ostrov, Miguel Jimenez, Sonja Billerbeck and their coworkers at Columbia University's Cornish Lab described how they genetically altered yeast so it could detect disease-causing pathogens and turn red. First, they swapped out one of the yeast’s receptors for one that recognized the pathogen Candida albicans, which can cause life-threatening infections. Then, Ostov explained, "we engineered into it the tomato pigment for red color called lycopene, and when the yeast detects the pheromone of other organisms in its surroundings, it will turn red." The change happens in fewer than three hours.
Versatile test kit
By replacing the baker's yeast gene with similar genes from other fungal species, the researchers showed the biosensor could detect nine additional human, agricultural and food spoilage pathogens. And the dipstick test detected pathogens in soil, urine, serum and blood. It was still effective after being stored at room temperature for 38 weeks.
Simplicity, however, was not the researchers’ only goal.
Co-author Miguel Jimenez said, "The idea we had was really, could we build a diagnostic device that was very, very cheap, basically the cost of just the sugar that feeds the yeast and that would be the only expensive reagent required? And we thought if it was so cheap, people outside the lab could use it all the time for continuous surveillance of pathogens."
Another advantage is the yeast-based tester could be easily manufactured in developing countries, because, as Jimenez noted, "Every country can make beer!"
The researchers have developed a prototype and are working to get it to places that need it.