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. 2000 Jul;44(7):1911-6.
doi: 10.1128/AAC.44.7.1911-1916.2000.

Amphotericin B resistance and membrane fluidity in Kluyveromyces lactis strains

M Younsi  1 , E Ramanandraibe, R Bonaly, M Donner, J Coulon
Affiliations

Amphotericin B resistance and membrane fluidity in Kluyveromyces lactis strains

M Younsi et al. Antimicrob Agents Chemother. 2000 Jul.

Abstract

The membrane fluidity of reduced-amphotericin B (AmB)-sensitivity Kluyveromyces lactis mutant strain is higher than that of the wild-type K. lactis strain. After culture of the K. lactis and K. lactis mutant cells in the presence of subinhibitory doses of AmB (10 and 125 mg/liter, respectively), the plasma membranes of both yeast strains also showed a higher fluidity than did those of control cells. High membrane fluidity was associated with changes in the structural properties of the membranes. Culture of the K. lactis and K. lactis mutant cells in the presence of AmB induced changes in membrane lipid contents. In particular, phospholipid contents were increased in both strains treated with AmB, compared with their corresponding counterparts. As a result, the sterol/phospholipid ratio decreased. The relative proportion of monounsaturated fatty acids also increased after AmB treatment. The saturated fatty acid/monounsaturated fatty acid ratio decreased in K. lactis and K. lactis mutant cells treated with AmB but also in K. lactis mutant control cells compared to that in the K. lactis wild strain. These changes in lipid composition explain the higher fluidity, which could represent a process of metabolic resistance of the yeasts to AmB.

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Figures

FIG. 1
FIG. 1
Kinetics of spheroplast formation from K. lactis and K. lactis mutant strains. The curves correspond to the percentage of spheroplasts obtained during the incubation period with lysing enzyme. The K. lactis and K. lactis mutant strains were grown in a Sabouraud liquid medium without (control) or with AmB and harvested during their exponential growth stage. ■, K. lactis control; □, K. lactis with 10 mg of AmB, ●, K. lactis mutant control, ○, K. lactis mutant with 125 mg of AmB.
FIG. 2
FIG. 2
Spheroplast stability versus buffer ionic strength. The curves correspond to the percentage of stable spheroplasts in relation to the decrease of buffer ionic strength. ■, K. lactis control, □, K. lactis with 10 mg of AmB, ●, K. lactis mutant control, ○, K. lactis mutant with 125 mg of AmB.
FIG. 3
FIG. 3
Spheroplast stability versus incubation time. The curves correspond to the percentage of stable spheroplasts in relation to the incubation period. ■, K. lactis control, □, K. lactis with 10 mg of AmB, ●, K. lactis mutant control, ○, K. lactis mutant with 125 mg of AmB.
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