Aims: To investigate intracellular localization of nickel and its chemical
nature in Pseudomonas aeruginosa.
Methods and Results: Transmission electron micrographs of Ni-loaded bacteri
a exhibited a darkened electron opaque zone throughout the cell periphery.
Energy dispersive X-ray analysis confirmed the deposition of metallic nicke
l. Cell fractionation revealed that 88% of the accumulated nickel was restr
icted 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 predomi
nant 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.