Development of a whole cell biosensor for the detection of inorganic mercury

A whole cell bacterial biosensor was developed by modification of chromosomal DNA of an environmental bacterial isolate Sphingobium SA2. The sensing element contained green fluorescence protein gene gfp fused to short segment of merA gene of Sphingobium SA2. The sensing element was introduced into electro-competent cells of Sphingobium SA2, where it integrated into the bacterial DNA due to homologous recombination. The transformed cells were able to produce green fluorescence in 5 h in the presence of nano-molar concentrations of mercury. A linear positive correlation was observed between 0-40 nm Hg and fluorescence intensity.