Biology of Metals

, Volume 4, Issue 2, pp 100–106 | Cite as

Silver tolerance and accumulation in yeasts

  • Martin Kierans
  • A. Morven Staines
  • Heather Bennett
  • Geoffrey M. Gadd
Original Articles

Summary

Debaryomyces hansenii (NCYC 459 and strain 75-21),Candida albicans (3153A),Saccharomyces cerevisiae (X2180-1B),Rhodotorula rubra (NCYC 797) andAureobasidium pullulans (IMI 45533 and ATCC 42371) were grown on solid medium supplemented with varying concentrations of AgNO3. Although Ag+ is highly toxic towards yeasts, growth on solid media was still possible at Ag concentrations of 1–2 mM. Further subculture on higher Ag concentrations (up to 5 mM) resulted in elevated tolerance. The extent of Ag tolerance depended on whether Ag-containing plates were exposed to light prior to inoculation since light-mediated reduction of Ag+ to Ag0 resulted in the production of a less toxic silver species. Experimental organisms exhibited blackening of colonies and the surrounding agar during growth on AgNO3-containing medium especially at the highest Ag concentrations tested. All organisms accumulated Ag from the medium; electron microscopy revealed that silver was deposited as electron-dense granules in and around cell walls and in the external medium. X-ray microprobe analysis indicated that these granules were metallic Ag0 although AgCl was also present in some organisms. Volatile and non-volatile reducing compounds were produced by several test organisms which presumably effected Ag+ reduction to Ag0.

Key words

Silver tolerance Silver accumulation Yeasts 

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Martin Kierans
    • 1
  • A. Morven Staines
    • 1
  • Heather Bennett
    • 1
  • Geoffrey M. Gadd
    • 1
  1. 1.Department of Biological SciencesUniversity of DundeeDundeeUK

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