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  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Relationship between cadmium sensitivity and degree of plasma membrane fatty acid unsaturation in Saccharomyces cerevisiae (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 539-545 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The sensitivity of Saccharomyces cerevisiae to the redox-active metal copper has recently been found to be influenced by cellular fatty acid composition. This study sought to investigate whether fatty acid composition affected plasma membrane permeabilisation and whole-cell toxicity induced by the redox-inactive metal cadmium. S. cerevisiae NCYC 1383 was enriched with the polyunsaturated fatty acids linoleate (18:2) and linolenate (18:3) by growth in 18:2- or 18:3-supplemented medium. Incorporation of the exogenous fatty acids resulted in them comprising more than 65% of the total fatty acids in plasma membrane lipids. Inhibition of cell division in the presence of Cd(NO3)2 was accentuated by growth in the presence of a polyunsaturated fatty acid. Furthermore, susceptibility to Cd2+-induced plasma membrane permeabilisation increased with the degree of fatty acid unsaturation. Thus, during exposure to Cd2+, K+ efflux from 18:2- and 18:3-enriched cells was up to 2.5-fold or 3-fold greater, respectively than that from unsupplemented cells. In addition, reductions in cell viability during exposure to Cd2+ were most marked in polyunsaturated-fatty-acid-supplemented cells. At certain times, unsupplemented Cd2+-exposed cells displayed up to 7-fold greater viability than supplemented Cd2+-exposed cells. The study demonstrates that the toxicity of the redox-inactive metal Cd2+ towards S. cerevisiae becomes markedly amplified with increased cellular and plasma membrane fatty acid unsaturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051093
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Manganese uptake and toxicity in magnesium-supplemented and unsupplemented Saccharomyces cerevisiae (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 180-184 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The magnesium content of Saccharomyces cerevisiae was found to vary by up to fivefold at differing␣ stages of batch growth and during growth in the presence of differing magnesium concentrations. Excess Mg was primarily sequestered in vacuoles. Mn2+-uptake experiments revealed that Mg-enriched cells had a markedly reduced capacity for Mn2+ accumulation. For example, after 6 h incubation in the presence of 50 μM Mn2+, Mn levels were approximately twofold higher in cells previously grown in unsupplemented medium than in those from Mg-supplemented medium. These differences were further accentuated at higher Mn2+ concentrations and were not attributable to altered cell-surface charge or altered cell-surface Mn2+ binding. Cellular Mg status also influenced Mn toxicity towards S. cerevisiae. During exposure to 5 mM Mn2+, 50% reductions in the viability of cells with initial Mg contents of approximately 1400 and 2700 nmol (109 cells)−1 occurred after approximately 1.6 h and 3.6 h respectively. In cells containing 3300 nmol Mg (109 cells)−1, more than 75% viability was still maintained after 7 h incubation with 5 mM Mn2+. It is concluded that Mn2+ uptake and toxicity in S. cerevisiae are strongly influenced by intracellular Mg, possibly through Mg-dependent regulation of divalent-cation transport activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050909
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Manganese toxicity towards Saccharomyces cerevisiae : Dependence on intracellular and extracellular magnesium concentrations (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 751-757 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Inhibition of the growth of Saccharomyces cerevisiae was evident at concentrations of 0.5 mM Mn2+ or higher, but a tolerance to lower Mn2+ concentrations was observed. The inhibitory effects of 2.0 mM Mn2+ were eliminated by supplementing the medium with excess Mg2+ (10 mM), whereas addition of excess Ca2+ and K+ had negligible effect on Mn2+ toxicity. Growth inhibition by Mn2+, in the absence of a Mg2+ supplement, was attributed to Mn2+ accumulation to toxic intracellular levels. Mn levels in S. cerevisiae grown in Mg2+-supplemented medium were severalfold lower than those of cells growing in unsupplemented medium. Mn2+ toxicity was also influenced by intracellular Mg, as Mn2+ toxicity was found to be more closely correlated with the cellular Mg:Mn ratio than with cellular Mn levels alone. Cells with low intracellular levels of Mg were more susceptible to Mn2+ toxicity than cells with high cellular Mg, even when sequestered Mn2+ levels were similar. A critical Mg:Mn ratio of 2.0 was identified below which Mn2+ toxicity became acute. The results demonstrate the importance of intracellular and extracellular competitive interactions in determining the toxicity of Mn2+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051242
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    Paper (German National Licenses)
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