Cytological study of cell cycle of the pathogenic yeast Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic human pathogen belonging to basidiomycetous fungi and has unique properties in cell cycle progression. The purpose of this study was to measure the duration of the cell cycle in this yeast. Under standard liquid culture conditions (1% yeast extract, 1% polypeptone, and 1% glucose; 24 degrees C; and 150 rpm), the doubling time of exponentially growing C. neoformans was 132 +/- 16 min (mean +/- standard deviation), and the durations of the G1, S, G2, and M phases were about 71, 18, 25, and 18 min, respectively. DNA synthesis started before bud emergence, and finished by the time the size of the bud became 1/4 that of the mother cell. The doubling time of the daughter cells was about twice that of the mother cells. The spindle pole body was located on the outer nuclear envelope and showed a duplicated form from the G1 phase to the G2 phase. These data form a basis for further cell cycle study of C. neoformans.