PHOSPHATASE-MEDIATED HEAVY-METAL ACCUMULATION BY A CITOBACTER SP AND RELATED ENTEROBACTERIA

A Citrobacter sp. was reported previously to accumulate heavy metals a s cell-bound heavy metal phosphates. Metal uptake is mediated by the a ctivity of a periplasmic acid-type phosphatase that liberates inorgani c phosphate to provide the precipitant ligand for heavy metals present ed to the cells. Amino acid sequencing of peptide fragments of the pur ified enzyme revealed significant homology to the phoN product (acid p hosphatase) of some other enterobacteria. These organisms, together wi th Klebsiella pneumoniae, previously reported to produce acid phosphat ase, were tested for their ability to remove uranium and lanthanum fro m challenge solutions supplemented with phosphatase substrate. The cou pling of phosphate liberation to metal bioaccumulation was limited to the metal accumulating Citrobacter sp.; therefore the participation of species-specific additional factors in metal bioaccumulation was sugg ested.