Demergasso Cecilia, Escudero Lorena, Casamayor Emilio O, Chong Guillermo, Balagué Vanessa, Pedrós-Alió Carlos
Centro de Biotecnología, Universidad Católica del Norte, Avda. Angamos 0610, Antofagasta, Chile.
Extremophiles. 2008 Jul;12(4):491-504. doi: 10.1007/s00792-008-0153-y. Epub 2008 Mar 18.
Lake Tebenquiche is one of the largest saline water bodies in the Salar de Atacama at 2,500 m above sea level in northeastern Chile. Bacteria inhabiting there have to deal with extreme changes in salinity, temperature and UV dose (i.e., high environmental dissimilarity in the physical landscape). We analyzed the bacterioplankton structure of this lake by 16S rRNA gene analyses along a spatio-temporal survey. The bacterial assemblage within the lake was quite heterogeneous both in space and time. Salinity changed both in space and time ranging between 1 and 30% (w/v), and total abundances of planktonic prokaryotes in the different sampling points within the lake ranged between two and nine times 10(6) cells mL(-1). Community composition changed accordingly to the particular salinity of each point as depicted by genetic fingerprinting analyses (denaturing gradient gel electrophoresis), showing a high level of variation in species composition from place to place (beta-diversity). Three selected sites were analyzed in more detail by clone libraries. We observed a predominance of Bacteroidetes (about one third of the clones) and Gammaproteobacteria (another third) with respect to all the other bacterial groups. The diversity of Bacteroidetes sequences was large and showed a remarkable degree of novelty. Bacteroidetes formed at least four clusters with no cultured relatives in databases and rather distantly related to any known 16S rRNA sequence. Within this phylum, a rich and diverse presence of Salinibacter relatives was found in the saltiest part of the lake. Lake Tebenquiche included several novel microorganisms of environmental importance and appeared as a large unexplored reservoir of unknown bacteria.
特本科伊切湖是智利东北部海拔2500米的阿塔卡马盐沼中最大的咸水体之一。栖息在那里的细菌必须应对盐度、温度和紫外线剂量的极端变化（即物理景观中高度的环境差异）。我们通过16S rRNA基因分析，在一项时空调查中对该湖的浮游细菌结构进行了分析。湖内的细菌群落无论在空间还是时间上都相当不均匀。盐度在空间和时间上都有所变化，范围在1%至30%（w/v）之间，湖内不同采样点浮游原核生物的总丰度在2×10⁶至9×10⁶个细胞/毫升之间。如基因指纹分析（变性梯度凝胶电泳）所示，群落组成随每个点的特定盐度而变化，表明不同地点的物种组成存在高度差异（β多样性）。通过克隆文库对三个选定地点进行了更详细的分析。我们观察到，相对于所有其他细菌类群，拟杆菌门（约占克隆的三分之一）和γ-变形菌门（另占三分之一）占主导地位。拟杆菌门序列的多样性很大，并且显示出显著的新颖性。拟杆菌门形成了至少四个聚类，数据库中没有与其培养亲缘关系的物种，并且与任何已知的16S rRNA序列的亲缘关系都相当远。在这个门中，在湖最咸的部分发现了丰富多样的盐杆菌亲缘物种。特本科伊切湖包含几种具有环境重要性的新型微生物，似乎是一个尚未被充分探索的未知细菌的巨大宝库。
