Demergasso Cecilia, Casamayor Emilio O, Chong Guillermo, Galleguillos Pedro, Escudero Lorena, Pedrós-Alió Carlos
Departamento de Química, Universidad Católica del Norte, Antofagasta, Chile.
FEMS Microbiol Ecol. 2004 Apr 1;48(1):57-69. doi: 10.1016/j.femsec.2003.12.013.
Athalassohaline lakes are inland saline aquatic environments with ionic proportions quite different from the dissolved salts in seawater. Prokaryotes inhabiting athalassohaline environments are poorly known and very few of such places have been surveyed for microbial diversity studies around the world. We analyzed the planktonic bacterial and archaeal assemblages inhabiting several of these evaporitic basins in a remote and vast area in northern Chile by PCR-denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene fragments. Most systems were springs and athalassohaline ponds in different saltflats of the Atacama Desert region, including Salar de Llamará (in the Central Depression), Salar de Atacama (in the Pre-Andean Depression) and Salar de Ascotán (in the Altiplano). Overall, we analyzed more than 25 samples from 19 different environments with strong gradients of altitude, qualitative ionic compositions and UV influence. Between 4 and 25 well-defined DGGE bands were detected for Bacteria in each sample, whereas Archaea ranged between 1 and 5. Predominant DGGE bands (defined by intensity and frequency of appearance) were excised from the gel and sequenced. Bacterial assemblages were dominated by the Cytophaga-Flavobacterium-Bacteroides (CFB) phylum and a few Proteobacteria. There was a tendency for increasing contribution of CFB with higher salinities and altitude. Thus, CFB accounted for the major fraction of band intensity in the Ascotán samples and for lower percentages in Atacama and Llamará. When the distribution of particular CFB sequences was examined, there were several relatives of Psychroflexus torquis substituting each other as salinity changed in Ascotán. Another set of CFB sequences, very distantly related to Cytophaga marinovorus, was abundant in both Llamará and Atacama at salinities lower than 7%. Archaeal assemblages were dominated by uncultured haloarchaea distantly related to cultured strains mostly obtained from thalassohaline environments. Most of the archaeal sequences did not have a close match with environmental 16S rRNA genes deposited in the database either. Therefore, athalassohaline environments are excellent sources of new microorganisms different from their counterparts in thalassohaline sites and useful tools to relate microbial genetic diversity and environmental characteristics such as changes in salinity (both qualitative and quantitative) and altitude.
无潮次盐度湖是内陆咸水水生环境，其离子比例与海水中溶解盐的离子比例有很大不同。人们对栖息于无潮次盐度环境中的原核生物了解甚少，全球范围内对这类地方进行微生物多样性研究的调查也非常少。我们通过聚合酶链反应-变性梯度凝胶电泳（PCR-DGGE）和16S rRNA基因片段测序，分析了智利北部一个偏远广阔地区几个蒸发盐盆地中的浮游细菌和古菌群落。大多数系统是阿塔卡马沙漠地区不同盐沼中的泉水和无潮次盐度池塘，包括拉马腊盐沼（位于中央凹陷处）、阿塔卡马盐沼（位于前安第斯凹陷处）和阿斯克坦盐沼（位于高原地区）。总体而言，我们分析了来自19个不同环境的25多个样本，这些环境具有强烈的海拔梯度、定性离子组成和紫外线影响。每个样本中检测到4至25条清晰的细菌DGGE条带，而古菌的条带数在1至5条之间。从凝胶中切下优势DGGE条带（根据强度和出现频率定义）并进行测序。细菌群落以噬纤维菌-黄杆菌-拟杆菌门（CFB）和少数变形菌门为主。随着盐度和海拔的升高，CFB的贡献有增加的趋势。因此，CFB在阿斯克坦样本中占条带强度的主要部分，在阿塔卡马和拉马腊样本中所占百分比较低。当检查特定CFB序列的分布时，随着阿斯克坦盐度的变化，有几种嗜冷弯曲菌的亲缘种相互替代。另一组与海洋噬纤维菌关系非常远的CFB序列，在盐度低于7%的拉马腊和阿塔卡马样本中都很丰富。古菌群落以与大多数从海洋盐度环境中获得的培养菌株关系较远的未培养嗜盐古菌为主。大多数古菌序列与数据库中保存的环境16S rRNA基因也没有密切匹配。因此，无潮次盐度环境是不同于海洋盐度环境中微生物的新型微生物的极佳来源，也是关联微生物遗传多样性与环境特征（如盐度变化（定性和定量）和海拔）的有用工具。
