Development of a Specific and Sensitive Bacteria Sensor for Detection of Mercury at Picomolar Levels in Environment

Abstract

A new whole-cell bacterial sensor for the detection of low concentration of mercury in environment was constructed by gene fusion between a mercury resistance (mer) operon from pMR26 of Pseudomonas strain K-62 and a promoterless luxAB gene from Vibrio harveyi. The luminescence-based biosensor was evaluated for the selectivity and sensitivity of the detection of mercury. Cadmium, lead, chromium and zinc ions did not interfere with the assay even at same concentration compared to Hg²⁺. Methylmercury, phenylmercury and mercuric sulfide also did not affect the biosensor. These results reveal that the specificity of the construct is restricted to bioavailable Hg²⁺. The sensitivity of the biosensor was improved by decreasing the cell density in the bioassay in addition to genetically expressing an Hg²⁺ transport system which was expected to increase the amount of mer operon-inducing mercury in the cytoplasm. In optimized assay conditions, the lowest detectable concentration of Hg²⁺ was 2 pM with 1 ml sample. This detection limit is enough to detect this compound in many contaminated and some pristine environmental samples.