Genes involved in cadmium resistance in Caulobacter crescentus

A transposon library of 5700 mutants was constructed in Caulobacter crescentus strain NA1000. Thirteen mutant strains were isolated that presented growth deficiency in the presence of 20 μM cadmium chloride, and the disrupted genes were identified by DNA sequencing. Among the predicted products were found two putative transcriptional regulators, one histidine kinase/response regulator hybrid protein, two 2Fe-2S family proteins, and also members of a putative metal efflux system. Certain of these mutants also showed an increased sensitivity to zinc and copper, and the genes encoding the efflux system were induced by cadmium and zinc, indicating that this system may be important for homeostasis of both metal ions.