28株隐球菌ITS基因序列测定及其系统进化分析

Phylogenetic analysis of 28 Cryptococcus strains based on their ITS sequences

目的测定28株鸽粪中分离的隐球菌的转录间隔区(internal transcribed spacer,ITS)序列,并根据ITS序列构建28株隐球菌和6株新生隐球菌的系统进化树。方法应用neighbor-joining(NJ)和m aximumparsimony(MP)方法构建系统进化树,研究隐球菌属不同菌种间的亲缘和进化分化关系。结果两种聚类方法得到的进化树模型基本一致,所有菌株聚类为3个主要分支:6株分离到的新生隐球菌和6株参考菌株为一支;大部分DHP和XSQ菌株聚为一支,除HP6外,所有的HP菌株和XSQ46-1及XSQ59-3,聚类为平行的第3个分支。从分化远近看,新生隐球菌分支、DHP和XSQ分支的分化年代没有显著差异。结论隐球菌属中,所有的新生隐球菌聚类为一支,其余的隐球菌菌种均分散在不同分支中,没有明显的种属聚集性,即呈现了隐球菌属不均一的特性。

Objective To sequence the internal transcribed spacer （ITS） regions of 28 Cryptococcus strains isolated from pigeon dropping samples and construct phylogenetic trees of 28 Cryptococcus strains and 6 Cryptococcus neoformans strains according the ITS sequences. Methods The phylogenetic trees were constructed by using neighbor-joining method and maximum parsimony method to analyze phylogenetic relationships among them and 6 references of Cryptococcus neoformans. Results All Cryptococcus strains were clustered into 3 branches, and 6 Cryptococcus neoformans strains and 6 reference strains were clustered in 1 branch. Except HP6, all HP strains and XSQ46-1 and XSQ59-3 were clustered into the same branch. Together with HP6, the DHP and XSQ strains were clustered together. According to the length of the branchs, there were no obvious differences among three main branches. Conclusion The Cryptococcus neoformans was clustered as an independent branch, however, the rest Cryptoeoccus species dispersed in other two branches, that is the heterogeneity of Cryptococcus genus as reported by others.