1887

Abstract

SUMMARY: The yeast-mycelium dimorphism of was studied in continuous culture in a defined medium. At a constant dilution rate (0.08 h) the morphological status of the culture could be controlled by the input concentration of Zn. As the input concentration of Zn was increased (in intervals from 0 to 7.6 μM) the culture shifted from a zinc-limited to a carbon-limited state. In this interval the culture gradually passed through three growth regimes based on morphology and concentration of exopolysaccharide and biomass. The first growth regime was found when the input concentration of Zn was kept below 0.45 μM. Growth in this regime was zinc-limited and more than 90% of the biomass was in the yeast growth form. An increase in the input concentration of Zn in this growth regime led to a proportional increase in both the biomass and the concentration of exopolysaccharide. When the input concentration of Zn was varied between 0.45 μM and 0.80 μM a second growth regime could be detected where simultaneous limitations in two nutrients were recognized. Although the carbon source (glucose) was exhausted an increase in the input concentration of Zn led to a proportional increase in the steady-state biomass concentration. The increase in biomass concentration was at the expense of exopolysaccharide production, which gradually decreased. The culture, still being primarily limited by Zn, remained in the yeast growth form. In a third growth regime (input concentration of Zn above 0.80 μM) no increase in the steady-state biomass was seen when the input concentration of Zn was increased. The concentration of residual glucose and exopolysaccharide was close to zero, and no further carbon could be diverted to an increase in the biomass. Glucose was the primary limiting nutrient. Increasing the input concentration of Zn in this growth regime led to a gradual increase in the mycelial growth form at the expense of the yeast growth form. More than 90% of the biomass was in the mycelial growth form when an input concentration of Zn of 7.6 μM was used.

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/content/journal/micro/10.1099/00221287-139-12-3065
1993-12-01
2019-11-12
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-139-12-3065
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