Bergen M S, Voss E, Soll D R
Department of Biology, University of Iowa, Iowa City 52242.
J Gen Microbiol. 1990 Oct;136(10):1925-36. doi: 10.1099/00221287-136-10-1925.
The 'white-opaque transition' in Candida albicans strain WO-1 provides a unique system for analysing high-frequency switching at the cellular level because of the difference in the budding phenotypes of the white and opaque phases. Single white and opaque cells were placed on agar and monitored for the dynamics of cell division, microcolony genesis and switching to the alternative phase. It is demonstrated that at 24 degrees C, opaque cells can switch directly to white cells but white cells first generate an elongate, pseudohyphal-shaped precursor in the transition to an opaque cell. Cells in either phase can generate a daughter cell in the alternative phase, then revert immediately to the genesis of subsequent daughter cells in the original phase. By developing a mathematical model for switching at the cellular level which subtracts mother cells and switched daughter cells from the pool of switching candidates, the probability for an opaque cell to generate a white daughter cell in any single generation was calculated to be 1.0 x 10(-1) and the probability for a white cell to generate an opaque daughter cell in any single generation was calculated to be 1.7 x 10(-5) at 24 degrees C on nutrient agar. The mean number of generations before an opaque cell generated a white daughter cell was calculated to be 3.4 and the mean number before a white cell formed an opaque cell was calculated to be 15.8 at 24 degrees C on nutrient agar. Finally, high-temperature induction of the opaque to white transition was analysed at the cellular level and demonstrated to involve frequent bipolar formation of white daughter cells on the original opaque mother cell, and in some cases intermediate phenotypes.
白色念珠菌WO-1菌株中的“白-不透明转变”提供了一个独特的系统，用于在细胞水平分析高频转换，因为白色和不透明阶段的出芽表型存在差异。将单个白色和不透明细胞置于琼脂上，监测细胞分裂、微菌落形成以及向另一阶段转换的动态过程。结果表明，在24℃时，不透明细胞可直接转换为白色细胞，但白色细胞在向不透明细胞转换过程中首先产生一个细长的假菌丝状前体。任一阶段的细胞都可产生处于另一阶段的子细胞，然后立即恢复为在原阶段产生后续子细胞。通过建立一个细胞水平转换的数学模型，从转换候选池中减去母细胞和已转换的子细胞，计算得出在24℃的营养琼脂上，不透明细胞在任何单一代中产生白色子细胞的概率为1.0×10⁻¹，白色细胞在任何单一代中产生不透明子细胞的概率为1.7×10⁻⁵。计算得出在24℃的营养琼脂上，一个不透明细胞产生白色子细胞之前的平均代数为3.4，一个白色细胞形成不透明细胞之前的平均代数为15.8。最后，在细胞水平分析了不透明向白色转变的高温诱导情况，结果表明这涉及在原始不透明母细胞上频繁出现白色子细胞的双极形成，并且在某些情况下会出现中间表型。
