Microbial eukaryote diversity and evolution in extraordinary environments

特殊环境下的微生物真核生物多样性和进化

• 批准号: 298366-2009
• 负责人: Simpson, Alastair
• 金额: $ 2.48万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2010
• 资助国家: 加拿大
• 起止时间: 2010-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=456849
• 关键词: Microbial; eukaryote; diversity; evolution; extraordinary

Free-living protozoa represent a large fraction of species and higher groups of eukaryotic organisms (i.e. everything more complex than bacteria), however, our understanding of their biodiversity lags way behind that of other eukaryotes, e.g. animals, plants, fungi, algae, and parasites. This project seeks to understand the biodiversity of protozoa in extraordinary habitats that are often considered to have very few eukaryotic organisms in them at all: anoxic habitats (were there is little or no oxygen), and hypersaline habitats (where the concentration of salt is 3-10 times that in normal seawater). We will culture small free-living protozoa from these habitats, and use comparisons of gene sequences to determine their evolutionary relationships to each other, and to previously isolated protozoa from these habitats and from other environments. We aim to understand whether protozoa have become adapted to these environments on few occasions or many occasions in evolutionary history. Some of the organisms will represent new higher taxa (maybe the equivalent of new 'phyla'), and will be described in detail using electron microscopy, and further DNA sequence characterisation and analysis. In the case of anoxic protozoa we will also obtain DNA sequences for particular groups directly from the environment, and compare them to the sequences from cultured species: This will allow us to determine whether the species we have in culture are a good representation, or a poor representation, of the actual diversity of these organisms present in nature. In the case of protozoa from hypersaline habitats we see a strange phenonemon where some of the protozoa that live in extremely saline water look exactly the same as protozoa that are found in marine samples. We will compare gene sequences from multiple isolates of thse 'identical' marine and hypersaline protozoa to determine how genetically similar they actually are, and whether they segregate into distinct evolutionary groups based on the salinity they grow best at. This will contribute to understanding what a species really is (if anything) the world of complex, possibly asexual microbes.

自由生活的原生动物代表了真核生物的大部分物种和更高的群体（即比细菌更复杂的一切），然而，我们对它们的生物多样性的了解远远落后于其他真核生物，如动物、植物、真菌、藻类和寄生虫。该项目旨在了解通常被认为只有很少真核生物的特殊栖息地中的原生动物的生物多样性：缺氧栖息地（氧气很少或没有氧气）和高盐栖息地（盐浓度是正常海水的3-10倍）。我们将从这些栖息地培养小型的自由生活的原生动物，并使用基因序列的比较来确定它们彼此之间的进化关系，以及之前从这些栖息地和其他环境中分离出来的原生动物。我们的目标是了解原生动物在进化史上是在少数场合还是在许多场合适应了这些环境。其中一些生物将代表新的高级分类群（可能相当于新的“门”），并将使用电子显微镜和进一步的DNA序列表征和分析进行详细描述。在缺氧原生动物的情况下，我们还将直接从环境中获得特定群体的DNA序列，并将它们与培养物种的序列进行比较：这将使我们能够确定我们在培养中的物种是否代表了自然界中存在的这些生物的实际多样性。在高盐栖息地的原生动物中，我们发现了一个奇怪的现象，一些生活在极咸水中的原生动物看起来和海洋样本中的原生动物一模一样。我们将比较这些“相同”的海洋原生动物和高盐原生动物的多个分离株的基因序列，以确定它们实际上在基因上有多相似，以及它们是否根据最适合生长的盐度分化成不同的进化群体。这将有助于理解一个物种到底是什么（如果有的话）——一个复杂的、可能无性繁殖的微生物世界。