The respiratory activities of osmotolerant fungus Aspergillus candidus were studied to evaluate its response to high osmotic stress. The rate of respiration by the whole cells and mitochondrial fractions increased with elevated sucrose concentrations in the growth medium. The activity of respiratory enzymes such as, succinate dehydrogenase, NADH dehydrogenase, cytochrome oxidase, NADH oxidase and succinoxidase was higher in the cells grown in the presence of high sucrose concentrations, ranging from 1.2 -2.1 times higher than the control. Whereas, NADH dehydrogenase exhibited the highest increase at 50 and 80% sucrose, it increased 6 and 13 times respectively higher than in the control. Electron microscopic observations of A. candidus grown at high osmotic stress revealed a larger size of mitochondria than in the control grown cells. The mean mitochondrial diameter at 50 and 80% sucrose was approximately 2 fold larger than in the control cells grown at 3% sucrose.
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M. A. Hefnawy, M. M. Gharieb and A. A. Abou-Seda, 2001. Mitochondrial Response to Osmotic Stress in Aspergillus candidus. Journal of Biological Sciences, 1: 1098-1100.
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