The role of an active transport mechanism in glycerol accumulation during osmoregulation by Zygosaccharomyces rouxii |
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Authors: | Petrus Jakobus van Zyl Stephanus Gouws Kilian Bernard Alexander Prior |
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Institution: | (1) Department of Microbiology and Biochemistry, University of the Orange Free State, P. O. Box 339, 9300 Bloemfontein, Republic of South Africa |
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Abstract: | Summary At water activities (a
w) of 0.998 (no osmoticum) and 0.960 a
w(NaCl), the affinity (K
m) of glycerol transport by Zygosaccharomyces rouxii was 25.6 and 6.4 mmol/l respectively. The maximum uptake rate (V
max) was ca. 2.3 mol/g/min at both a
w's. However, at an a
wof 0.960 using polyethylene glycol (PEG) 400 the K
mand V
max for glycerol transport increased to 61.1 mmol/l and 32.2 mol/g per minute respectively. This suggests that different glycerol transport mechanisms operate during stress by the two osmotica. The addition of uncouplers (2,4-dinitrophenol or carbonylcyanide-m-chlorophenylhydrazine) resulted in the outflow of accumulated 14C]glycerol from Z. rouxii after on osmotic upshock indicating that an active transport mechanism was operative. The transport mechanism was specific for glycerol since other polyols (mannitol, meso-erythritol and arabitol) had no effect on the uptake rate. During upshock from 0.998 to 0.960 a
w(NaCl), a transient increases in the rate of 14C]glycerol uptake was observed. However, if PEG 400 was used as osmoticum, the rate of glycerol uptake failed to increase.Offprint requests to: P. J. van Zyl |
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Keywords: | |
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