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Appl Environ Microbiol. 1990 December; 56(12): 3649-3656
Copyright © 1990, American Society for Microbiology. All Rights Reserved.

Binding of Dissolved Strontium by Micrococcus luteus

Brendlyn D. Faison^*, Carmen A. Cancel, Susan N. Lewis and Howard I. Adler

Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6194

ABSTRACT

Resting cells of Micrococcus luteus have been shown to remove strontium (Sr) from dilute aqueous solutions of SrCl₂ at pH 7. Loadings of 25 mg of Sr per g of cell dry weight were achieved by cells exposed to a solution containing 50 ppm (mg/liter) of Sr. Sr binding occurred in the absence of nutrients and did not require metabolic activity. Initial binding was quite rapid (<0.5 h), although a slow, spontaneous release of Sr was observed over time. Sr binding was inhibited in the presence of polyvalent cations but not monovalent cations. Ca and Sr were bound preferentially over all other cations tested. Sr-binding activity was localized on the cell envelope and was sensitive to various chemical and physical pretreatments. Bound Sr was displaced by divalent ions or by H⁺. Other monovalent ions were less effective. Bound Sr was also removed by various chelating agents. It was concluded that Sr binding by M. luteus is a reversible equilibrium process. Both ion exchange mediated by acidic cell surface components and intracellular uptake may be involved in this activity.

^* Corresponding author.

Present address: Chemical Technology Department, Universidad de Puerto Rico, Arecibo, PR 00613-1806.

Present address: Office of Operational Readiness and Safety, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6256.

Present address: Medical Sciences Division, Oak Ridge Associated Universities, Oak Ridge, TN 37831-0117.