新月细柱藻的分离培养及形态和分子鉴定

Isolation of Cylindrotheca closterium and Its Morphological and Molecular Identifications

自胶州湾分离培养2株微藻(MGB0401和MGB0402)。经形态学鉴定为新月细柱藻(Cylindrotheca closterium)。MGB0401和MGB0402的18S核糖体RNA基因(rDNA)扩增片段长度为1775 bp,存在10个碱基差异。MGB0401和MGB0402的rbcL基因扩增片段长度为1190 bp,有45个碱基差异,对应的氨基酸序列存在4个氨基酸残基差异。系统学分析表明,2株微藻与已知新月细柱藻相应序列亲缘关系最近。微藻常用系统学分析用基因的序列不仅是分类鉴定的补充指标,也是不同研究结果相互比较的重要基础。

Cylindrotheca closterium is a benthic diatom. It is extremely difficult to distinguish this species from Nitzschia longissima under light microscopy. Two strains of Cylindrotheca closterium were isolated from Jiaozhou Bay in August 2004 with their nuclear-encoded SSU rDNA and chloroplast-encoded rbcL gene amplified, cloned and sequenced. SSU rDNA sequences of two strains is 0.56% different （10 in 1 775 bp）. However, their rbcL gene is 3.78 96 divergent （45 in 1 190 bp）. Four amiono acid residues of the deduced amino acid sequences of their rbcL genes are different. Phylogenetic analyses using of both SSU rDNA and rbcL genes support that the assignment of two strains to genus Cylindrotheca. The sequences of marker genes widely used in phylogenetic analyss are very important references of species identification. They can provide also comparison basis of data from different sources.