Single-input gates. A) Tetracycline responsive YES gates. B) β-estradiol sensing NOT gates. In both cases, a single operator guarantees higher signal separation whereas two operators permit to achieve a stronger repression. Fluorescence levels of the open gates (indicated with their yeast strain name–see Additional file 1) correspond to blue columns. Gates’ schemes are drawn with SBOL  icons (all the symbols used throughout the paper are shown in Additional file 1: Figure S1).