Development of a user-friendly IdgS-Sfp based whole-cell biosensor for high-performance Hg(II) detection in environmental samples

Mercury (Hg) is a toxic heavy metal that primarily accumulates and biotransforms in water bodies. Though accurate, instrumental detection methods often have high thresholds, making them unsuitable for frequent monitoring. This study introduces a novel whole-cell biosensor that utilizes the IdgS-Sfp system to biosynthesize indigoidine, a water-soluble blue pigment. This approach eliminates the need for extraction methods typically used for lipophilic pigments. The biosensor employs genetically engineered E. coli strains equipped with optimized genetic circuits. Key enhancements include incorporating the MerC transport protein and optimizing induction temperature and time to improve sensitivity and expand the detection range. The IdgS-Sfp-based biosensor exhibits high sensitivity with a limit of detection of 0.08 nM and a broad quantitative range of 2.44–156.25 nM. It shows high selectivity for Hg(II) even in the presence of multiple metal ions and maintains robust performance across various environmental water matrices, including freshwater and seawater. This biosensor offers a promising tool for rapid and cost-effective Hg(II) detection in environmental samples with potential environmental monitoring applications.