Utilizing Whole-Cell Biosensors to Measure Ionic Mercury in Water Samples

Whole-cell biosensors (WCBs) are instrumental platforms for discovering and characterizing regulatory elements and advancing bioengineering. They also hold immense promise for environmental and food monitoring. While significant efforts have been invested in enhancing their sensitivity and portability, the standardization of their handling and data analysis remains relatively underdeveloped. This article presents a comprehensive guide to utilizing two recently developed WCBs, Mer-Blue and Mer-RFP, proven capable of detecting ionic mercury at levels below the World Health Organization's drinking water limits. The protocols detailed herein encompass microbial culture preparation, sensor calibration, data acquisition, and analysis. For the fluorometric Mer-RFP biosensor, a novel biosynthesis allocation theorem is employed to identify the time interval for reliable and accurate dose-response measurements. For the colorimetric Mer-Blue biosensor, a low-cost camera setup enables rigorous measurements in settings lacking expensive spectrophotometers and fluorimeters, facilitating decentralized pollution monitoring. The procedures used for testing freshwater samples are described, and the limitations of these biosensors with respect to sample types are discussed. By sharing these handling and analysis techniques, we encourage broader research groups to adopt and improve these biological devices for developing effective environmental monitoring solutions. Ultimately, this research aims to facilitate the widespread adoption of biosensor technologies within the environmental science community, contributing to more effective and efficient monitoring of trace element pollution in various ecosystems.