Enzymically mediated bioprecipitation of uranium by a Citrobacter sp.: a concerted role for exocellular lipopolysaccharide and associated phosphatase in biomineral formation

Article Abstract:

Research reveals that uranyl phosphate deposition occurs in Citrobacter species through the accumulation of uranyl ion precipitated by phosphate. Data further point out that phosphate groups of the lipopolysaccharide and phosphatase enzyme mediate the metal deposition.

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Phosphatase production and activity in Citrobacter freundii and a naturally occurring, heavy-metal-accumulating Citrobacter sp.

Article Abstract:

The Citrobacter strain, N14, accumulates cadmium, lanthanum and uranyl ions in its cells by the activity of acid phosphatase. The formation of this enzyme is controlled by the pho regulon. Acid phosphatase formation increases in the absence of carbon and its activity decreases in the presence of Cd stress. The acid phosphatase produced by C. freundii is similar to that produced by strain N14. The strain N14 is less sensitive to Cd2+ and Zn2+ and more sensitive to Cu2+ at pH 5 as compared to C. freundii.

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Localization of enzymically enhanced heavy metal accumulation by Citrobacter sp. and metal accumulation in vitro by liposomes containing entrapped enzyme

Article Abstract:

The possible application of the encapsulated enzyme for metal removal in vitro was analyzed in Citrobacter sp. with the use of an in vitro system which was constructed using artificial membrane vesicles with entrapped phosphatase. Results reveal that metal accumulation as a cell-bound metal phosphate is mediated by periplasmically located phosphatase that is associated with the outer membrane.

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