Specific and sensitive detection of small molecules is needed to address multiple societal challenges, from disease diagnosis to water quality monitoring. Many relevant analytes must be measured in a centralized laboratory facility, preventing their detection in many contexts. Increasing the accessibility of molecular detection requires low cost sensing technologies which can be operated at the point of need by an untrained user. We meet this need by developing a sensing platform which integrates engineered bacteria into a simple, wireless circuit which can be read via smartphone. Our device incorporates the electroactive microbe Shewanella oneidensis, which is engineered to secrete electrons in the presence of an analyte. This microbial activity actuates a connected resonant frequency identification (RFID) tag, which wirelessly signals to nearby devices only when the analyte is absent. We first apply this system to detect paraoxon, a potent neurotoxin and widespread pollutant. We then demonstrate the generality of this platform by engineering S. oneidensis to detect a suite of plant nutrients, enabling comprehensive monitoring of agricultural soil quality. These sensors require no specialized equipment or training and are constructed using less than $1.00 of materials. We anticipate that this technology will make small molecule detection broadly accessible, enhancing our ability to treat disease, remediate pollution, and maintain agricultural productivity.
