Unité d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, Orsay, France.
PLoS One. 2011;6(12):e28767. doi: 10.1371/journal.pone.0028767. Epub 2011 Dec 14.
The geomicrobiology of crater lake microbialites remains largely unknown despite their evolutionary interest due to their resemblance to some Archaean analogs in the dominance of in situ carbonate precipitation over accretion. Here, we studied the diversity of archaea, bacteria and protists in microbialites of the alkaline Lake Alchichica from both field samples collected along a depth gradient (0-14 m depth) and long-term-maintained laboratory aquaria. Using small subunit (SSU) rRNA gene libraries and fingerprinting methods, we detected a wide diversity of bacteria and protists contrasting with a minor fraction of archaea. Oxygenic photosynthesizers were dominated by cyanobacteria, green algae and diatoms. Cyanobacterial diversity varied with depth, Oscillatoriales dominating shallow and intermediate microbialites and Pleurocapsales the deepest samples. The early-branching Gloeobacterales represented significant proportions in aquaria microbialites. Anoxygenic photosynthesizers were also diverse, comprising members of Alphaproteobacteria and Chloroflexi. Although photosynthetic microorganisms dominated in biomass, heterotrophic lineages were more diverse. We detected members of up to 21 bacterial phyla or candidate divisions, including lineages possibly involved in microbialite formation, such as sulfate-reducing Deltaproteobacteria but also Firmicutes and very diverse taxa likely able to degrade complex polymeric substances, such as Planctomycetales, Bacteroidetes and Verrucomicrobia. Heterotrophic eukaryotes were dominated by Fungi (including members of the basal Rozellida or Cryptomycota), Choanoflagellida, Nucleariida, Amoebozoa, Alveolata and Stramenopiles. The diversity and relative abundance of many eukaryotic lineages suggest an unforeseen role for protists in microbialite ecology. Many lineages from lake microbialites were successfully maintained in aquaria. Interestingly, the diversity detected in aquarium microbialites was higher than in field samples, possibly due to more stable and favorable laboratory conditions. The maintenance of highly diverse natural microbialites in laboratory aquaria holds promise to study the role of different metabolisms in the formation of these structures under controlled conditions.
尽管类陨石坑湖微生物岩在进化上与一些太古代类似物相似，因为它们以原地碳酸盐沉淀为主，而不是以增生为主，但由于其复杂性，它们的地质微生物学仍然知之甚少。在这里，我们研究了碱性湖 Alchichica 的微生物岩中的古菌、细菌和原生生物的多样性，这些微生物岩是从沿深度梯度（0-14 米深度）采集的野外样本和长期维持的实验室水族箱中获得的。使用小亚基 (SSU) rRNA 基因文库和指纹图谱方法，我们检测到了广泛的细菌和原生生物多样性，而古菌的比例较小。好氧光合作用生物主要由蓝细菌、绿藻和硅藻组成。蓝细菌多样性随深度而变化，Oscillatoriales 主导浅中和微生物岩，Pleurocapsales 主导最深的样品。早期分支的 Gloeobacterales 在水族箱微生物岩中代表了很大的比例。厌氧光合作用生物也多种多样，包括 Alpha-proteobacteria 和 Chloroflexi 的成员。尽管光合微生物在生物量中占主导地位，但异养生物类群的多样性更高。我们检测到多达 21 个细菌门或候选门的成员，包括可能参与微生物岩形成的谱系，如硫酸盐还原的 Delta-proteobacteria，但也包括 Firmicutes 和非常多样的可能能够降解复杂聚合物物质的类群，如 Planctomycetales、Bacteroidetes 和 Verrucomicrobia。异养真核生物主要由真菌（包括基础 Rozellida 或 Cryptomycota 成员）、领鞭毛生物、Nucleariida、变形虫、Alveolata 和 Stramenopiles 组成。许多真核生物谱系的多样性和相对丰度表明原生生物在微生物岩生态学中发挥了意想不到的作用。许多来自湖泊微生物岩的谱系在水族箱中成功维持。有趣的是，水族箱微生物岩中检测到的多样性高于野外样本，这可能是由于实验室条件更稳定和有利。在实验室水族箱中维持高度多样化的天然微生物岩有望在受控条件下研究不同代谢物在这些结构形成中的作用。
