Taton Arnaud, Grubisic Stana, Brambilla Evelyne, De Wit Rutger, Wilmotte Annick
Laboratoire d'Algologie, de Mycologie et de Systématique Expérimentale, Institut de Botanique B22, Université de Liège, B-4000 Liège, Belgium.
Appl Environ Microbiol. 2003 Sep;69(9):5157-69. doi: 10.1128/AEM.69.9.5157-5169.2003.
Currently, there is no consensus concerning the geographic distribution and extent of endemism in Antarctic cyanobacteria. In this paper we describe the phenotypic and genotypic diversity of cyanobacteria in a field microbial mat sample from Lake Fryxell and in an artificial cold-adapted sample cultured in a benthic gradient chamber (BGC) by using an inoculum from the same mat. Light microscopy and molecular tools, including 16S rRNA gene clone libraries, denaturing gradient gel electrophoresis, and sequencing, were used. For the first time in the study of cyanobacterial diversity of environmental samples, internal transcribed spacer (ITS) sequences were retrieved and analyzed to complement the information obtained from the 16S rRNA gene. Microscopy allowed eight morphotypes to be identified, only one of which is likely to be an Antarctic endemic morphotype. Molecular analysis, however, revealed an entirely different pattern. A much higher number of phylotypes (15 phylotypes) was found, but no sequences from Nodularia and Hydrocoryne, as observed by microscopy, were retrieved. The 16S rRNA gene sequences determined in this study were distributed in 11 phylogenetic lineages, 3 of which were exclusively Antarctic and 2 of which were novel. Collectively, these Antarctic sequences together with all the other polar sequences were distributed in 22 lineages, 9 of which were exclusively Antarctic, including the 2 novel lineages observed in this study. The cultured BGC mat had lower diversity than the field mat. However, the two samples shared three morphotypes and three phylotypes. Moreover, the BGC mat allowed enrichment of one additional phylotype. ITS sequence analysis revealed a complex signal that was difficult to interpret. Finally, this study provided evidence of molecular diversity of cyanobacteria in Antarctica that is much greater than the diversity currently known based on traditional microscopic analysis. Furthermore, Antarctic endemic species were more abundant than was estimated on the basis of morphological features. Decisive arguments concerning the global geographic distribution of cyanobacteria should therefore incorporate data obtained with the molecular tools described here.
目前，关于南极蓝细菌的地理分布和特有程度尚无共识。在本文中，我们描述了来自弗里克塞尔湖的野外微生物垫样本以及在底栖梯度室（BGC）中使用来自同一垫子的接种物培养的人工冷适应样本中蓝细菌的表型和基因型多样性。使用了光学显微镜和分子工具，包括16S rRNA基因克隆文库、变性梯度凝胶电泳和测序。在环境样本蓝细菌多样性研究中，首次检索并分析了内部转录间隔区（ITS）序列，以补充从16S rRNA基因获得的信息。显微镜观察鉴定出了8种形态型，其中只有一种可能是南极特有的形态型。然而，分子分析揭示了一种完全不同的模式。发现了更多的系统发育型（15个系统发育型），但未检索到显微镜观察到的结节藻属和水鞘藻属的序列。本研究确定的16S rRNA基因序列分布在11个系统发育谱系中，其中3个谱系仅存在于南极，2个谱系是新发现的。总体而言，这些南极序列与所有其他极地序列一起分布在22个谱系中，其中9个谱系仅存在于南极，包括本研究中观察到的2个新谱系。培养的BGC垫子的多样性低于野外垫子。然而，这两个样本共有三种形态型和三种系统发育型。此外，BGC垫子使一种额外的系统发育型得以富集。ITS序列分析揭示了一个难以解释的复杂信号。最后，本研究提供了证据表明南极蓝细菌的分子多样性远大于目前基于传统显微镜分析所知道的多样性。此外，南极特有物种比根据形态特征估计的更为丰富。因此，关于蓝细菌全球地理分布的决定性论据应纳入此处所述分子工具获得的数据。
