The genes zntA and zntR encoding a P-type ATPase and its activator confer zinc and cadmium resistance in Chromobacterium violaceum

Abstract

The transition metal zinc is an essential trace element for life but becomes toxic at high concentrations. In the opportunistic pathogen Chromobacterium violaceum, zinc acquisition is crucial for virulence, yet how this bacterium copes with zinc toxicity remains unknown. In this work, we demonstrate that C. violaceum senses and responds to excess zinc by activating the zntA gene, which encodes a P_1B-2-type ATPase, via the transcriptional regulator ZntR. Phenotypic analyses by growth curves, disk diffusion, and CFU assays revealed that both ΔzntA or ΔzntR mutant strains exhibited increased sensitivity to zinc and cadmium. The ΔzntA mutant showed increased zinc and cadmium accumulation, suggesting that ZntA functions as an efflux pump. The expression of zntA increased in the presence of zinc and cadmium in the wild-type strain, but not in the ΔzntR mutant strain, indicating that ZntR activates zntA under conditions of zinc or cadmium excess. The role of ZntA in vivo was analyzed using the social amoeba Dictyostelium discoideum as a host cell. Plaque assays indicated that the C. violaceum ΔzntA mutant strain was more susceptible than the C. violaceum wild-type strain to clearance by D. discoideum knockout strains with altered intracellular zinc allocation. Overall, our data reveal that the genes zntA and zntR encoding a P_1B-2-type ATPase and its transcriptional activator are key determinants of zinc and cadmium resistance in C. violaceum, ensuring bacterial survival under zinc-stress conditions encountered in the environment and the host.