大部分白念珠菌为a/α菌株，同时具备MTLa位点和MTLα位点，交配的发生率很低。白念珠菌的a/α菌株必须首先在MTL 位点上形成纯合状态，形成a/a或α/α菌株，再通过重要的White-Opaque转换步骤，才具备交配能力。研究者在临床分离的白念珠菌中观察到有趣的现象即与自然环境分离株相比，临床分离株中存在较高的a/α菌株Opaque表型。鉴于Opaque表型是具有交配能力的表型及部分前期实验结果，我们推测Opaque表型a/α白念珠菌在人体内环境中也能进行交配。基于上述假设，本研究针对白念珠菌自然株及临床分离株中Mating type及White-Opaque表型差异，研究白念珠菌临床分离a/α菌株中Opaque表型的细胞特征、White-Opaque表型转换机制及对于白念珠菌致病性的影响，对于解开白念珠菌有性生殖生活周期之谜，及交配对于白念珠菌致病性的作用具有非常重要的意义。

Since Hull and Johnson identified the mating type-like (MTL) locus in C.albicans' genome in 1999, after more than 10 years investigation, it is now becoming evident that C. albicans exhibits an unique sexual cycle, including a phenotypic transition called "White-Opaque" switching. In nature, most C.albicans strains were a/α?strains, in which two alleles existed in the mating type locus, MTLa and MTLα. Before Mating, an a/αstrain would have to undergo homozygosis to a/a or α/α, and then undergo a complex phenotypic transition from the white to the opaque phase. This reversible transition was between the normal yeast morphology (white) to an elongated cell type opaque, which is the mating-cometent form of this fungus..We found an interesting phenomenon that higher percentage of a/α?opaque cells were observed in clinical isolates than natural isolates. Because opaque was mating-competent cells, based on our partial preliminary liboratory data, we hypothesized that opaque a/α ?strain would be mating in host niche..In this context, this research focused on the difference in mating type and white-opaque phase between natural strain and clinical strain, study the microbiologic characteristics, switch mechanism of opaque a/α?cell and the relationship between this phenomenon and pathogenesis in host.