Clinical and environmental isolates of Cryptococcus gattii from Australia that retain sexual fecundity
Clinical and environmental isolates of Cryptococcus gattii from Australia that retain sexual fecundity
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DOI：
10.1128/ec.4.8.1410-1419.2005
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发表时间：
2005-08-01
期刊：
影响因子：
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通讯作者：
Heitman, J
中科院分区：
文献类型：
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作者：
Campbell, LT;Fraser, JA;Heitman, J
格特隐球菌是一种主要的致病性酵母，在动物和人类中引起疾病。它与新型隐球菌（Cryptococcus neoformans）密切相关，并与4000万年前的共同祖先有分歧。虽然C gattii有一个特征性的性周期依赖于基因组的二型区域称为MAT基因座，交配很少在这个物种中观察到。在这项研究中，我们确定了第一次临床（包括人类和兽医）和环境分离，从澳大利亚保留性繁殖力。从不同的地理位置的120个分离物的集合进行了分析的分子类型，交配型，并与肥沃的测试菌株共培养时，发展交配结构的能力。9个分离物产生双孢丝与成对的核，融合钳连接，和担孢子。三个基因（URA5、MAT α特异性SXI 1 α基因和MAT α特异性SXI 2a基因）的DNA序列分析分别揭示了URA5和SXI 2a的很少或没有变异性。然而，在测序的108个MAT α菌株中，发现SXI 1 α基因以11种不同的等位基因存在。系统发育分析发现，大多数变异发生在更肥沃的基因型。虽然一些血统的澳大利亚C gattii保留了交配的能力，大多数菌株是不育的，这表明无性繁殖是在这些人群中的主导模式。
Cryptococcus gattii is a primary pathogenic yeast that causes disease in both animals and humans. It is closely related to Cryptococcus neoformans and diverged from a common ancestor similar to 40 million years ago. While C gattii has a characterized sexual cycle dependent upon a dimorphic region of the genome known as the MAT locus, mating has rarely been observed in this species. In this study, we identify for the first time clinical (both human and veterinary) and environmental isolates from Australia that retain sexual fecundity. A collection of 120 isolates from a variety of geographic locations was analyzed for molecular type, mating type, and the ability to develop mating structures when cocultured with fertile tester strains. Nine isolates produced dikaryotic filaments with paired nuclei, fused clamp connections, and basidiospores. DNA sequence analysis of three genes (URA5, the MAT alpha-specific SXI1 alpha gene, and the MATa-specific SXI2a gene) revealed little or no variability in URA5 and SXI2a, respectively. However across the 108 MAT alpha strains sequenced, the SXI1 alpha gene was found to exist as 11 different alleles. Phylogenetic analysis found most variation to occur in the more fertile genotypes. Although some lineages of Australian C gattii have retained the ability to mate, the majority of isolates were sterile, suggesting that asexuality is the dominant mode of propagation in these populations.