**4.1 Redox signaling in biological systems**

In response to redox imbalance, new metabolic pathways are initiated, the repair or bypassing of damaged cellular components is coordinated and systems that protect the cell from further damage are induced. Throughout the years, many studies have revealed a vast repertoire of elegant solutions that have evolved to allow bacteria to sense and respond to different redox signals [78]. Below, two oxidative stress sensors, SoxR and OxyR, and their corresponding signaling pathway will be introduced. These systems are later shown to enable electrical control of gene expression in *E. coli*.
