(click here for detailed information about circuit design)

We want the suicide part (ethanol) to be opened only after the first way (kill protein) fails; that is, Nosema infection is too severe to be killed by kill protein (defensin).

As a result, we add several terminators behind ROS/oxyR complex-induced promoter to build a threshold for RNA polymerase to overcome. In other words, it takes RNA polymerase much more time to go through the terminator barrier and thus, create a time lag for ethanol production.

Nevertheless, if we put the ethanol synthesizing enzymes PDC and ADH right after these terminators, it will take much time to accumulate the enzyme’s effective concentration for ethanol production because a lot of effort is wasted to overcome terminator's threshold over and over again. Therefore, instead of having ROS/oxyR complex regulate ethanol production directly, we constructed a circuit that has a “key”, another activator (the key we choose is T7 polymerase)to amplify the production of PDC and ADH so that ethanol concentration can reach its effective level to kill the infected, incurable bees and save the whole colony.