Geotrichum Candidum の分節機序に関する研究

Abstract

Arthrospore formations in 5 strains of Geotrichum candidum were studied. These were distinguished into two groups by their ability for the spore formation. One group of the fungi (3 strains, G.C. IFO 6067, 6454 and Link. OUT 4665) showed no arthrospore formations even for several days or more in the shaking cultivation with 0.5% yeast extract in Sabouraud's glucose buillon (YSG) at 30 C. On the other hand other groups of the fungi (2 strains, G.C. IFO 5767 and Link OUT 4028) began to produce arthrospore only 8-9 hr after the inoculation and actively produced them for 24 hours. The arthrospore formations were studied in these fungi using synthetic medium and its mechanisms were discussed. Results were as follows. 1. The appearance of the short hyphae (under 25μm) but not of the segmentation seemed to precede the formation of the spore. 2. In the latter group of the fungi, the spore formation, which began 8-9 hr after the inoculation in YSG, delayed by a high concentration of phosphate. It supported that the environment somewhat affected gene expression. 3. Although the former group of the fungi had difficulty in producing the spore in YSG, the group rapidly produced the spore in the medium of a low concentration of phosphate. The nuclei in the hyphae cultured in this medium were small in number and randomly distributed in comparison with those one formed in the synthetic medium containing the standard concentration of phosphate. Thus the synthesis of the nuclei seemed to be active in the fungi cultured under the standard concentration of phosphate, and depressed in the case of the low concentration of phosphate. 4. When both groups of the fungi (G. C. IFO 5767 and 6067) were cultured in the phosphate free medium, every cell contained phosphate on the plasma membrane. The problem that whether the formation mechanism of arthrospore relates to gene expression or the plasma membrane remains to be studied in future.