Stimulation of Strontium Accumulation in Linoleate-Enriched Saccharomyces cerevisiae Is a Result of Reduced Sr2+ Efflux

Author

1. Simon V. Avery^*, 
2. Shareeka L. Smith, 
3. A. Mohamad Ghazi^†, and 
4. Michael J. Hoptroff^‡

-Author Affiliations

1. Department of Biology, University Plaza, Georgia State University, Atlanta, Georgia 30302-4010

ABSTRACT

The influence of modified plasma membrane fatty acid composition on cellular strontium accumulation in Saccharomyces cerevisiaewas investigated. Growth of S. cerevisiae in the presence of 1 mM linoleate (18:2) (which results in 18:2 incorporation to ∼70% of total cellular and plasma membrane fatty acids, with no effect on growth rate) yielded cells that accumulated Sr²⁺ intracellularly at approximately twice the rate ofS. cerevisiae grown without a fatty acid supplement. This effect was evident over a wide range of external Sr²⁺concentrations (25 μM to 5 mM) and increased with the extent of cellular 18:2 incorporation. Stimulation of Sr²⁺accumulation was not evident following enrichment of S. cerevisiae with either palmitoleate (16:1), linolenate (18:3) (n-3 and n-6 isomers), or eicosadienoate (20:2) (n-6 and n-9 isomers). Competition experiments revealed that Ca²⁺- and Mg²⁺-induced inhibition of Sr²⁺ accumulation did not differ between unsupplemented and 18:2-supplemented cells. Treatment with trifluoperazine (TFP) (which can act as a calmodulin antagonist and Ca²⁺-ATPase inhibitor), at a low concentration that precluded nonspecific K⁺ efflux, increased intracellular Sr²⁺accumulation by approximately 3.6- and 1.4-fold in unsupplemented and 18:2-supplemented cells, respectively. Thus, TFP abolished the enhanced Sr²⁺ accumulation ability of 18:2-supplemented cells. Moreover, the rate of Sr²⁺release from Sr²⁺-loaded fatty acid-unsupplemented cells was found to be at least twice as great as that from Sr²⁺-loaded 18:2-enriched cells. The influence of enrichment with other fatty acids on Sr²⁺efflux was variable. The results reveal an enhanced Sr²⁺ accumulation ability of S. cerevisiae following 18:2-enrichment, which is attributed to diminished Sr²⁺ efflux activity in these cells.

FOOTNOTES

• Received 12 August 1998.
• Accepted 7 December 1998.
• ↵* Corresponding author. Mailing address: Department of Biology, University Plaza, Georgia State University, Atlanta, GA 30302-4010. Phone: (404) 651-0912. Fax: (404) 651-2509. E-mail:biosva@panther.gsu.edu.
• ↵† Permanent address: Department of Geology, Georgia State University, Atlanta, GA 30303.
• ↵‡ Present address: Unilever RED, Port Sunlight Laboratory, Bebbington, Merseyside L63 3JW, United Kingdom.

• Copyright © 1999 American Society for Microbiology

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http://aem.asm.org/content/65/3/1191.abstract