一株海洋金藻的18S rRNA 基因序列分析及分类

Isochrysis sp.strain HG是一株分离自福建长乐自然海区的金藻,是一种良好的西施舌育苗饵料藻。显微形态观察表明,Isochrysis sp.strain HG的形态特性与等鞭金藻属的球等鞭金藻(I.galbana)和湛江等鞭金藻(I.zhanjiangensis)比较接近。进一步克隆Isochrysis sp.strain HG的核糖体小亚基(small subunit,SSU)18S rRNA基因,获得了长度为1780bp的基因序列。同源性分析表明,该序列与在NCBI数据库中登录的等鞭金藻属的18S rRNA基因序列同源性最高,说明结果与形态鉴定的结果相一致。基于18S rRNA基因序列的系统发育分析表明,Isochrysis sp.strain HG与等鞭金藻属的I.zhangjiangensis、Isochrysis sp.strain CCAP927/14、I.galbana和Isochrysis sp.strain Santou聚在一个分支类群上,其中I.zhangjiangensis与Isochrysis sp.strain CCAP927/14聚为一个独立的子类群,和I.galbana、Isochrysis sp.strain Santou以及目标菌株Isochrysis sp.strain HG形成4个并列独立的分支。根据形态及分子系统分析结果,Isochrysis sp.strain HG可能是不同于I.zhangjiangensis、I.galbana的等鞭金藻种类。

Identification and sequence analysis of the 18S rRNA gene of a marine microalgae

Isochrysis sp. strain HG, a potentially valuable bait-microalgae for Coelomactra antiquata, was isolated from the natural water of Changle, Fujian, China. It showed extremely similar morphological characteristics with the strains of Isochrysis genera I. galbana and I. zhanjiangensis under the microscopes. The 18S rRNA gene of Isochrysis sp. strain HG was cloned to further identify the strain at the molecular level. The homologous analysis shown that the 1780 bp derived from the 18S rDNA sequence was highly homologous to the relevant sequences of I. galbana and I. zhanjiangensis in GenBank. Furthermore, the phylogenetic tree based on the 18S rDNA Sequences was constructed, showing that the Isochrysis sp. strain HG, I. Zhangjiangensis, Isochrysis sp. strain CCAP927/14, I. galbana, and Isochrysis sp. strain Santou, were all clustered with together. Among them, I. zhangjiangensis subgroups with Isochrysis sp. strain CCAP927/14, and I. galbana, and Isochrysis sp. strain Santou;and Isochrysis sp. strain HG was further formed one of four subclades. Based on the morphological and molecular evidence, Isochrysis sp. strain HG was proposed to be a candidate species of Isochrysis genera, which is different from the other three Isochrysis species that have been previously described.