Bridging the mercury exposure threshold: Development and application of whole-cell biosensors incorporating biotransformation pathways.

Mercury is a toxic heavy metal prevalent in the environment, requiring sensitive and comprehensive detection methods to protect public health. Our study introduces transformative whole-cell biosensors with MerA and MerB biotransformation modules in Escherichia coli, enhancing the biosensors' capacity for high-sensitivity detection across a wide range of inorganic and organic mercury (Hg) concentrations, from nanomolar level to micromolar level. These biosensors achieve a limit of detection (LOD) of 1 nM for Hg(II) and 2 nM for MeHg, covering both low-level environmental exposure and high-level poisoning thresholds. They offer precise and consistent detection of biological samples, adhering to health standards such as the biological exposure limits set by the Occupational Safety and Health Administration (NIOSH). These limits specify a threshold of 0.053 μM for Hg in urine and 0.125 μM for Hg in blood for workers. This innovation offers a reliable early mercury exposure detection tool crucial for environmental monitoring and clinical diagnostics.