State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China.
PLoS One. 2011;6(11):e27597. doi: 10.1371/journal.pone.0027597. Epub 2011 Nov 18.
It is widely accepted that biodiversity is lower in more extreme environments. In this study, we sought to determine whether this trend, well documented for macroorganisms, also holds at the microbial level for bacteria. We used denaturing gradient gel electrophoresis (DGGE) with phylum-specific primers to quantify the taxon richness (i.e., the DGGE band numbers) of the bacterioplankton communities of 32 pristine Tibetan lakes that represent a broad salinity range (freshwater to hypersaline). For the lakes investigated, salinity was found to be the environmental variable with the strongest influence on the bacterial community composition. We found that the bacterial taxon richness in freshwater habitats increased with increasing salinity up to a value of 1‰. In saline systems (systems with >1‰ salinity), the expected decrease of taxon richness along a gradient of further increasing salinity was not observed. These patterns were consistently observed for two sets of samples taken in two different years. A comparison of 16S rRNA gene clone libraries revealed that the bacterial community of the lake with the highest salinity was characterized by a higher recent accelerated diversification than the community of a freshwater lake, whereas the phylogenetic diversity in the hypersaline lake was lower than that in the freshwater lake. These results suggest that different evolutionary forces may act on bacterial populations in freshwater and hypersaline lakes on the Tibetan Plateau, potentially resulting in different community structures and diversity patterns.
人们普遍认为，在更极端的环境中，生物多样性较低。在这项研究中，我们试图确定这种趋势是否也适用于微生物水平的细菌，因为这种趋势在宏观生物中已有充分的记录。我们使用具有门特异性引物的变性梯度凝胶电泳（DGGE）来量化 32 个原始西藏湖泊的浮游细菌群落的分类丰富度（即 DGGE 带数），这些湖泊代表了广泛的盐度范围（淡水到高盐度）。对于所研究的湖泊，盐度被发现是对细菌群落组成影响最大的环境变量。我们发现，在淡水生境中，细菌分类丰富度随着盐度的增加而增加，直到盐度值为 1‰。在盐度较高的系统（盐度大于 1‰的系统）中，并未观察到随着盐度进一步增加而导致分类丰富度预期下降的情况。这两种模式在两年内采集的两组样本中均得到一致观察。16S rRNA 基因克隆文库的比较表明，盐度最高的湖泊的细菌群落具有比淡水湖更高的近期加速多样化特征，而高盐湖泊的系统发育多样性低于淡水湖泊。这些结果表明，在青藏高原的淡水和高盐湖泊中，可能存在不同的进化力量作用于细菌种群，从而导致不同的群落结构和多样性模式。
