For this year's iGEM Competition, our team has focused on putting forward a biological approach to detecting nickel ions as a heavy metal contaminant in the natural environment. Through our study over this summer, we are expecting to control the expression of red fluorescent protein by changing the nickel ion concentration. In a certain concentration range, we will try to establish a quantitative relationship between the intensity of the fluorescence and the concentration of nickel ions in the environment. This may build a nickel ion concentration quantitative detection system.
In order to achieve this goal, we use a nickel-sensitive repressive promoter (pncrA). In the absence of nickel ions, the repressor protein (NcrB) binds to the promoter, preventing the expression of the subsequent gene. The nickel ions in the environment can bind to repressor proteins to alter the domain of the protein, so that the fluorescent protein gene behind the promoter is expressed and produces fluorescence.