Department of Biology, University of New Mexico, Albuquerque, NM, USA.
Geobiology. 2014 Jan;12(1):83-98. doi: 10.1111/gbi.12070. Epub 2013 Nov 29.
Hydrothermal springs harbor unique microbial communities that have provided insight into the early evolution of life, expanded known microbial diversity, and documented a deep Earth biosphere. Mesothermal (cool but above ambient temperature) continental springs, however, have largely been ignored although they may also harbor unique populations of micro-organisms influenced by deep subsurface fluid mixing with near surface fluids. We investigated the microbial communities of 28 mesothermal springs in diverse geologic provinces of the western United States that demonstrate differential mixing of deeply and shallowly circulated water. Culture-independent analysis of the communities yielded 1966 bacterial and 283 archaeal 16S rRNA gene sequences. The springs harbored diverse taxa and shared few operational taxonomic units (OTUs) across sites. The Proteobacteria phylum accounted for most of the dataset (81.2% of all 16S rRNA genes), with 31 other phyla/candidate divisions comprising the remainder. A small percentage (~6%) of bacterial 16S rRNA genes could not be classified at the phylum level, but were mostly distributed in those springs with greatest inputs of deeply sourced fluids. Archaeal diversity was limited to only four springs and was primarily composed of well-characterized Thaumarchaeota. Geochemistry across the dataset was varied, but statistical analyses suggested that greater input of deeply sourced fluids was correlated with community structure. Those with lesser input contained genera typical of surficial waters, while some of the springs with greater input may contain putatively chemolithotrophic communities. The results reported here expand our understanding of microbial diversity of continental geothermal systems and suggest that these communities are influenced by the geochemical and hydrologic characteristics arising from deeply sourced (mantle-derived) fluid mixing. The springs and communities we report here provide evidence for opportunities to understand new dimensions of continental geobiological processes where warm, highly reduced fluids are mixing with more oxidized surficial waters.
热液泉孕育了独特的微生物群落，使人们深入了解生命的早期演化，扩大了已知微生物的多样性，并记录了深部地球的生物圈。然而，中温（凉爽但高于环境温度）大陆泉在很大程度上被忽视了，尽管它们可能也拥有独特的微生物种群，这些微生物受到深部地下流体与近地表流体混合的影响。我们研究了美国西部不同地质区的 28 个中温泉的微生物群落，这些泉展示了深部和浅层循环水的不同混合方式。对群落的非培养分析产生了 1966 个细菌和 283 个古菌 16S rRNA 基因序列。这些泉水中含有多样的分类群，并且在不同地点之间共享的操作分类单位（OTU）很少。变形菌门在整个数据集（所有 16S rRNA 基因的 81.2%）中占主导地位，其余的由 31 个其他门/候选门组成。一小部分（约 6%）的细菌 16S rRNA 基因不能在门水平上进行分类，但主要分布在那些有大量深部来源流体输入的泉水中。古菌多样性仅限于仅四个泉水中，并且主要由特征明确的泉古菌组成。整个数据集的地球化学变化很大，但统计分析表明，更多深部来源流体的输入与群落结构相关。那些输入较少的含有通常存在于地表水的属，而一些输入较多的泉可能含有潜在的化能自养群落。这里报告的结果扩展了我们对大陆地热系统微生物多样性的理解，并表明这些群落受到深部（地幔衍生）流体混合产生的地球化学和水文特征的影响。我们报告的这些泉水和群落为了解温暖、高度还原的流体与更氧化的地表水混合的大陆地球生物学过程的新维度提供了证据。
