Changes in the levels of soluble carbohydrates during growth of Pyricularia oryzae.
1988
Hwang B.K. | Kim K.D.
The changes in mycelial soluble carbohydrates of Pyricularia oryzae, which occurred during starvation, and afterwards, in the regrowth medium, were determined by gas chromatography. Trehalose, glucose, fructose, and mannitol were present in the mycelial extracts. Trehalose and mannitol were the major products of sugar assimilation. During starvation of P. oryzae, glucose, fructose, and mannitol were rapidly exhausted, but trehalose levels remained relatively high within the mycelium. The high amount of trehalose accumulated when the fungus utilized glucose in lag phase of regrowth. The conversion of glucose to mannitol in P. oryzae took place slowly with a maximum accumulation in the stationary phase of growth. However, the trehalose level varied with the composition of glucose substrates in the medium. During regrowth the fungus absorbed almost all glucoses from the medium, thereby maintaining the maximum growth of mycelium. The increased quantity of glucose within P. oryzae cultured on the increased concentrations of glucose in the regrowth medium is likely due to the uptake of more external glucoses from the higher glucose-medium. The synthesis of trehalose, fructose, and mannitol was not affected by the concentration of glucose in medium. Increasing the nitrate in the external medium did not affect the carbohydrate metabolism and further mycelial growth. Ammonium nitrate, as a nitrogen source, was less available for carbohydrate metabolism in P. oryzae than potassium nitrate and urea. Glucose and trehalose taken up from the medium were not converted to fructose within the mycelium. Trehalose was also not converted to mannitol. Our data suggest that sucrose, potassium nitrate or urea are adequate as carbon and nitrogen sources in the medium for carbohydrate metabolism in P. oryzae and its growth.
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