In total eight (A,B,..,H) different configurations of repressor binding sites were tested (Figure 4). Two: F and H, were found to be produce Kill-switch systems robust towards variations in binding strengths and production rates. The result of the best scoring configuration H has been magnified (figure 5). The repressor binding site configuration corresponding to this map has the highest chance of working in an experimental set-up. The x-axis shows the fold change in protein production, the y-axis has increased binding strengths for individual repressors by an order of magnitude each row. The color map indicates that increases in repressor binding strengths can be compensated for by increased production rates of either the target gene or decreased production of the repressor itself. The practical implications for constructing the an optimized version of the Kill-switch were as follows: two TetR repressor binding sites on the LacI promoter, two LacI and one CIλ repressor binding site on the TetR promoter, two TetR and one CIλ repressor binding site on the toxin promoter.