Protistan diversity estimates based on 18S rDNA from seawater incubations in the western North Atlantic
Protistan diversity estimates based on 18S rDNA from seawater incubations in the western North Atlantic
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DOI：
10.1111/j.1550-7408.2005.05202006.x
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发表时间：
2005-03-01
影响因子：
2.2
通讯作者：
Caron, DA
中科院分区：
文献类型：
--
作者：
Countway, PD;Gast, RJ;Caron, DA
核糖体RNA基因（rDNA）的克隆/测序和片段分析已成为微生物分类群鉴定的常用方法。这些基因的序列为物种提供了许多额外的分类特征，否则就没有什么独特的形态特征，或者需要涉及显微镜或实验室培养和测试。这些相同的方法现在正在应用于自然微生物群落的生态学研究中，取得了巨大的成功。通过对环境样本进行遗传分析，并将所得到的遗传信息与已建立的（和迅速增长的）公共数据库进行比较，正在迅速积累有关天然微生物组合组成的广泛信息。采用两种分子生物学方法对北大西洋西部沿海天然海水样本中的真核微生物多样性进行了研究：rRNA基因的克隆和测序，以及末端限制性片段长度多态性（T-RFLP）方法对这些基因进行片段分析。当将海水样品置于容器中并在环境光和温度下孵育72小时时，进行了一项简单的实验，以检查天然微生物组合的整体真核生物（主要是原生生物）多样性和物种组合（种型多样性）的变化。将天然海水样品置于容器中，在三个时间点(时间0、时间-24小时，时间-72小时)。然而，在三个采样时间之间，特定真核生物种型的优势发生了实质性变化。研究中观察到的种型总数中只有18%在所有三个时间点都被观察到，而65%（165个中的108个）的种型仅在单个时间点被观察到（最初54个独特的种型，24 h时37个独特的种型，72 h时17个）。本研究结果表明，原生物分类群在原始海水样品中以极低的丰度存在较高的多样性，因此在群落结构的初步表征中未被观察到。遏制导致这些分类群的优势地位发生重大变化，使以前未观察到的种型在孵育24或72小时后得以记录。
Cloning/sequencing and fragment analysis of ribosomal RNA genes (rDNA) are becoming increasingly common methods for the identification of microbial taxa. Sequences of these genes provide many additional taxonomic characters for species that otherwise have few distinctive morphological features, or that require involved microscopy or laboratory culture and testing. These same approaches are now being applied with great success in ecological studies of natural communities of microorganisms. Extensive information on the composition of natural microbial assemblages is being amassed at a rapid pace through genetic analyses of environmental samples and comparison of the resulting genetic information with well-established (and rapidly growing) public databases. We examined microbial eukaryote diversity in a natural seawater sample from the coastal western North Atlantic Ocean using two molecular biological approaches: the cloning and sequencing of rRNA genes and by fragment analysis of these genes using the terminal restriction fragment length polymorphism (T-RFLP) method. A simple experiment was carried out to examine changes in the overall eukaryote (largely protistan) diversity and species cornposition (phylotype diversity) of a natural microbial assemblage when a seawater sample is placed in a container and incubated at ambient light and temperature for 72 h. Containment of the natural seawater sample resulted in relatively minor changes in the overall eukaryote diversity (species richness) obtained by either molecular method at three time points (time-zero, time-24 h, time-72 h). However, substantial changes in the dominance of particular eukaryote phylotypes took place between the three sampling times. Only 18% of the total number of phylotypes observed in the study were observed at all three time points, while 65% (108 of 165) phylotypes were observed only at a single time point (54 unique phylotypes initially, 37 more unique phylotypes at 24 h, and 17 more at 72 h). The results of this study indicate that a high diversity of protistan taxa existed in the original seawater sample at very low abundance, and thus were not observed in the initial characterization of community structure. Containment resulted in significant shifts in the dominance of these taxa, enabling the presence of previously unobserved phylotypes to be documented after 24 or 72 h of incubation.