Fig 6.

A schematic diagram showing the regulation of Cu tolerance and PCH biosynthesis by CzcS/CzcR during Zn excess in P. aeruginosa. Zn excess disrupts P. aeruginosa tolerance to Cu, while simultaneously, CzcS/CzcR is activated which induces the expression of ptrA to remedy the capability of P. aeruginosa to tolerate Cu stress. Zn is also shown to induce the expression of pchR, which leads to the overproduction of PCH and enhanced growth under Fe-depleted conditions. Concurrently, CzcS/CzcR antagonizes the induction of pchR during Zn excess by the direct binding of CzcR to the promoter of pchR to inhibit its expression.