Inexpensive biosensors made from engineered yeast can detect 10 different fungi, including human pathogens, and can potentially identify other fungi, bacteria, and viruses. The biosensors could be put to work monitoring microorganisms that cause health problems, damage crops, or cause food to spoil (Sci. Adv. 2017, DOI: 10.1126/sciadv.1603221). Virginia W. Cornish, Nili Ostrov, Miguel Jimenez, and Sonja Billerbeck of Columbia University and coworkers, who developed and tested the biosensors, point out that current fungal tests, such as antibody and nucleic acid assays, often require specialized labs, refrigerated reagents, expensive instruments, and highly trained personnel. The new biosensor tests could cost less than a penny when mass-produced, the researchers estimate. The devices are dry, do not require refrigeration, and can be used by anyone. To create the biosensors, the researchers removed the surface receptor protein that yeast use to detect pheromones from mating partners and replaced it with receptors responsive to pheromones from other fungi, such as candida, which causes human yeast infections. They engineered the yeast so activation of the receptor turns on a biosynthetic pathway for lycopene, the compound that makes tomatoes red. In the presence of candida pheromone, the yeast turns red, a visual signal of the fungus.