Carbon Dioxide Fixation in Aspergillus oryzae Conidia at the Initial Phase of Germination

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Since CO₂ has been known to be one of the essential factors for the initiation of germination in Aspergillus oryzae conidia, the C¹⁴O²-fixation pattern in the germinating co-nidia was examined.
During the early phase of germination,
C¹⁴O² was rapidly incorporated into the 50% ethanol soluble fraction and then finally fixed in macromolecular substances, especially in RNA. The qualitative and quantitative analysis of the labeled compounds in the 50% ethanol soluble fraction by means of paper chromatography and autoradiography, followed by the radioactivity measurement of each spot, revealed that the major primary product of CO²-fixation is possibly malate. Some other dicarboxylic acids, amino acids and nucleotides were also identified in the fraction. Among nucleotides, uridine and adenine nucleotides were the major nucleotides so far detected in the conidia of early germination.
When the conidia were incubated in phosphate buffer, in which even the swelling of conidia and, in turn, the germination do not occur, the characteristic difference in the labeling pattern from that of germinating conidia was found in amino acids. In germi-nating conidia, amino acids labeled were glutamate, glutamine and aspartate, whereas in the “non-germinating” conidia only glutamate and aspartate were labeled ap-preciably. This finding suggests an important role of glutamine in the initiation of germina-tion.