Cadmium Accumulation by a Citrobacter sp.: the Chemical Nature of the Accumulated Metal Precipitate and its Location on the Bacterial Cells

1 Physical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK 2 Laboratory of Chemical Crystallography, University of Oxford, Parks Road, Oxford OX1 3PD, UK ABSTRACT SUMMARY: Cells of a strain of a Citrobacter sp., pre-grown in cadmium-free continuous culture, accumulated cadmium extensively when resuspended in a buffer that contained Cd 2+ and glycerol 2-phosphate. The accumulated compound was identified by X-ray microanalysis and magic angle spinning NMR analysis as cell-bound cadmium phosphate, probably CdHPO 4 . Its accumulation is consistent with the activity of a phosphatase, induced during pre-growth, that continues to function in the resuspended cells to liberate HPO 2- 4 from glycerol 2-phosphate. This anion then combines with Cd 2+ to form insoluble cell-bound CdHPO 4 . Present address: Microbiology Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.