Increasing the copper sensitivity of microorganisms by restricting iron supply, a strategy for bio-management practices

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Steunou, Anne Soisig | Bourbon, Marie-Line | Babot, Marion | Durand, Anne | Liotenberg, Sylviane | Yamaichi, Yoshiharu | Ouchane, Soufian

Edité par CCSD ; Wiley -

International audience. Pollution by copper (Cu$^{2+}$) extensively used as antimicrobial in agriculture and farming represents a threat to the environment and human health. Finding ways to make microorganisms sensitive to lower metal concentrations could help decreasing the use of Cu$^{2+}$ in agriculture. In this respect, we showed that limiting iron (Fe) uptake makes bacteria much more susceptible to Cu$^{2+}$ or Cd$^{2+}$ poisoning. Using efflux mutants of the purple bacterium $Rubrivivax\ gelatinosus$, we showed that Cu$ç+$ and Cd$^{2+}$ resistance relies on the expression of the Fur-regulated FbpABC and Ftr iron transporters. To support this conclusion, inactivation of these Fe-importers in the Cu$^+$ or Cd$^{2+}$ -ATPase efflux mutants gave rise to hypersensitivity towards these ions. Moreover, in metal overloaded cells the expression of FbpA, the periplasmic iron-binding component of the ferric ion transport FbpABC system was induced, suggesting that cells perceived an 'iron-starvation' situation and responded to it by inducing Fe-importers. In this context, the Fe-Sod activity increased in response to Fe homoeostasis dysregulation. Similar results were obtained for Vibrio cholerae and Escherichia coli, suggesting that perturbation of Fe-homoeostasis by metal excess appeared as an adaptive response commonly used by a variety of bacteria. The presented data support a model in which metal excess induces Fe-uptake to support [4Fe-4S] synthesis and thereby induce ROS detoxification system.

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