Berrendero Esther, Perona Elvira, Mateo Pilar
Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
Int J Syst Evol Microbiol. 2008 Feb;58(Pt 2):447-60. doi: 10.1099/ijs.0.65273-0.
In this study, a polyphasic approach was adopted to investigate natural freshwater (river and stream) samples of Rivularia colonies and isolated strains of cyanobacteria with a high degree of trichome tapering (genera Rivularia and Calothrix). Analysis of the phycocyanin (PC) operon and the intervening intergenic spacer (cpcBA-IGS) and 16S rRNA gene sequences were used for genetic characterization. In addition, a molecular fingerprinting method, temperature-gradient gel electrophoresis, which allows sequence-dependent separation of PCR products, was used to assess genotypic diversity in environmental samples and isolated strains. The results showed a high variability of the PC-IGS among the genotypes that was not associated with the morphologies observed. This study underlines the importance of choosing a low-nutrient-content culture medium, especially one with a low phosphorus concentration, for studying typical morphological features of Rivularia for taxonomic purposes. Molecular fingerprinting methods and morphological analyses confirmed the diversity in Rivularia colonial structure and trichome features corresponding to genetic diversity within a single colony. Phylogenetic analysis of cpcBA-IGS was largely consistent with that obtained from 16S rRNA gene sequence analysis and confirmed the high level of divergence between genotypes. The sequences of Rivularia and Calothrix from this study and database sequences showed great heterogeneity and were clearly not monophyletic. The results of this genetic and morphological study of field samples and fresh isolates indicated that the current classification of these genera needs to be revised.
在本研究中，采用了多相方法来研究念珠藻属菌落的天然淡水（河流和溪流）样本以及具有高度藻丝渐细特征的蓝藻分离菌株（念珠藻属和眉藻属）。通过分析藻蓝蛋白（PC）操纵子、中间的基因间隔区（cpcBA-IGS）和16S rRNA基因序列进行遗传特征分析。此外，还使用了一种分子指纹技术——温度梯度凝胶电泳，该技术可实现基于序列的PCR产物分离，用于评估环境样本和分离菌株中的基因型多样性。结果表明，基因型之间的PC-IGS具有高度变异性，且与所观察到的形态无关。本研究强调了选择低营养含量培养基的重要性，尤其是低磷浓度的培养基，以便为分类学目的研究念珠藻的典型形态特征。分子指纹技术和形态学分析证实了念珠藻菌落结构和藻丝特征的多样性与单个菌落内的遗传多样性相对应。cpcBA-IGS的系统发育分析在很大程度上与16S rRNA基因序列分析结果一致，并证实了基因型之间的高度分歧。本研究中念珠藻属和眉藻属的序列与数据库序列显示出很大的异质性，且明显不是单系的。对野外样本和新鲜分离株的遗传和形态学研究结果表明，这些属的当前分类需要修订。
