Schematic representation of domain organization and mode of action of phosphorelay two‐component systems. A. The ArcB/ArcA phosphorelay. This system belongs to the TRPR type of phosphorelay according to the classification proposed by Williams and Whitworth (2010). B. The TodS/TodT system that belongs to the TRTR type of phosphorelays. The sequence of phosphoryl group transfer is indicated. tm, transmembrane region; PAS, Per‐Arnt‐Sim type of sensor domain; TR, transmitter module comprised of a dimerization/histidine phosphotransfer domain and a catalytic domain; RRR, response regulator receiver domain; HPT, histidine containing phosphotransfer domain; DNA‐b, DNA‐binding domain.