Intracellular nickel accumulation by Pseudomonas aeruginosa and its chemical nature

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Aims:To investigate intracellular localization of nickel and its chemical nature in Pseudomonas aeruginosa.Methods and Results:Transmission electron micrographs of Ni-loaded bacteria exhibited a darkened electron opaque zone throughout the cell periphery. Energy dispersive X-ray analysis confirmed the deposition of metallic nickel. Cell fractionation revealed that 88% of the accumulated nickel was restricted to the periplasm and membrane. X-ray diffraction patterns ascertained the chemical nature of cellular Ni as phosphide (Ni5P4, NiP2 and Ni12P5) and carbide (Ni3C) crystals.Conclusions:Pseudomonas aeruginosa accumulated nickel as its phosphide and carbide crystal mostly in the cell envelope region, indicating the predominant role of phosphoryl and carboxyl/carbonyl groups of cell wall/membrane components in cation sequestration.Significance and Impact of the Study:The data contribute significantly to a better understanding of bacteria–metal interaction and will be useful in developing biotechnological strategies for toxic metal bioremediation.

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