<ORIGINAL>Study On the proliferative ability of chlamydospores of Candida albicans

Candida albicans is a dimorphic fungus proliferating by budding with oval yeast when cultured with Sabouraud agar medium at 37℃ ; when cultured with Corn meal agar medium at 25℃ or room temperature, it forms pseudohyphae with many blastospores on the connections of each hyphae and chlamydospores on the ends. Spores of fungi differentiating highly specialized cells generally proliferate for preservation of the species to germinate under optimal conditions. However, much fewer chlamydospores than blastospores are formed on the ends of pseudohyphae and the chlamydospores also have thick cell walls. As a result, chlamydospores are considered to be persistent. However, mature chlamydospores do not show nucleus and mitochondria and are nearly filled by vacuoles and spongoid vacuoles. Therefore it is not certain that chlamydospores possess the functions of spores that their name indicates. This study compared chlamydospores and blastospores to examine whether chlamydospores possessed proliferative ability and persistence. Blastospores and chlamydospores formed by the C. albicans 2S2 strain were isolated and preserved in 0.3CMG medium at 6℃. The proliferative ability and persistence of the spores were examined with Sabouraud agar, BHI blood agar, Sabouraud liquid, and BHI liquid media. Further the ultrastructure of each spores was observed with transmission electron microscopy and the chromosomal DNA was analyzed by agarose gel electrophoresis. The results were as follows: 1. Blastospores and chlamydospores were isolated by stir and shake methods from pseudohyphae so the spore functions were not damaged. 2. Blastospores maintained proliferative ability and germinated even after preservation in 0.3CMG medium at 6℃ for 96 hours. 3. Some chlamydospores preserved for 24 hours germinated and proliferated, but after preservation for 48 hours or longer they did not proliferate and persistence was inferior to that of blastospores. 4. All blastospores formed within 24 hours had nucleus and organelles. However, a large number of chlamydospores had no nucleus. 5. There were mitochondria in chlamydospores after preservation for 24 hours, after 48 hours there were many spongoid vacuoles, after 72 hours there were only spongoid vacuoles, and after 96 hours there was separation of cell membrane from cell wall. 6. The chromosomal DNA of preserved chlamydospores showed more fragmentation of DNA than blastospores at all preservation times. The results suggested that chlamydospores were dying off and had no proliferative ability and were not persistent.