Regulation of a nickel tolerance operon conserved in <i>Mesorhizobium</i> strains from serpentine soils

Bacteria employ diverse mechanisms for maintaining optimal intracellular levels of bioactive metals. Isolates of <i>Mesorhizobium</i> bacteria from Ni-rich serpentine soils possess a small genetic region controlling Ni efflux. This region is subject to transcriptional regulation via the small repressor protein NreA. In this work, the essential components of the NreA protein and the DNA operator with which it interacts are defined, enabling potential adaptation of this system for metal sensing or other technologies requiring a compact inducible gene expression module.