Another option are promoters that are inducible by heavy metals, such as: zinc, cadmium, cobalt, arsenic, nickel and chromium. Several such promoters were evaluated in Synechocystis sp. PCC6803 by Peca 2007. These promoters are not ideal, as metal ions are critical in Synechocystis’ metabolic pathways and altering concentrations can lead to compounding undesired side effects. Additionally, working with these promoters produces waste contaminated with heavy metals, increasing disposal costs
