Engineering ion channels for ultrahigh mercury sensitivity: Visual detection at critical environmental limits

This study aims to develop an ultrahigh-sensitivity whole-cell biosensor for detecting inorganic Hg(II) in environmental water samples. Whole-cell biosensors provide a cost-effective alternative to instrumental methods, but they often lack adequate sensitivity and have high thresholds for sensing signal readings. We incorporated Hg(II)-specific transport proteins MerC, MerT, and MerP into a decoupled genetic circuit, utilizing a deoxyviolacein (DV)-based visual whole-cell biosensor to overcome these limitations. The optimized biosensor reached a detection limit of 0.011 nM, significantly lower than the drinking water limit of 49.86 nM. Additionally, it can produce a visually readable signal at the mercury limits for Class I surface water and Class I seawater, which is set at 2.49 nM. In controlled laboratory conditions, the biosensor showed a strong specificity for Hg(II) and maintained a robust linear relationship across a wide concentration range of 0.092-46.875 nM. When tested with tap water, surface water, and seawater, the biosensor demonstrated excellent resistance to interference and stable performance, exhibiting a strong linear correlation within the Hg(II) concentration range of 0-12.5 nM. This study presents a novel and practical approach for cost-effective and high-throughput screening of mercury at critical environmental limits, offering a valuable tool for environmental monitoring.