| 翻訳と辞書 |
| Rare biosphere ： ウィキペディア英語版 |
Rare biosphere
Changes in the biodiversity of an ecosystem, whether marine or terrestrial, may affect its efficiency and function.〔Gitay ''et al.'', 2002〕 Disruption due to climate change, or other anthropogenic perturbations can result in decreased productivity and in some cases lead to disruptions in global biogeochemical cycles.〔 The possible ramifications of changes in ecosystem biodiversity are not well characterized or understood, and it may be possible that disruption, up to a point, will have little to no effect given the redundancy within an ecosystem.〔 This is particularly troubling in the context of microbial ecosystems. The dynamics of microbial ecosystems are tightly coupled to biogeochemical processes, and any perturbation within this system in particular could result in dramatic changes (Kirchman, 2008). For example, the microbial loop within the marine context is responsible for the decomposition of organics and recycling of nutrients back into the ecosystem. This allows for other organisms, such as phytoplankton, to reuse essential nutrients, like nitrogen, and continue production (Kirchman 2008). Without this recycled nitrogen, phytoplankton would be highly limited in their production rates, in turn limiting the growth of grazers. The effects of such an occurrence would reverberate throughout the food web, and nitrogen cycle. It is important to establish a base line of microbial diversity within ecosystems in order to gauge possible change due to climate change and the possible outcomes.
Recent use of high-throughput sequencing techniques has broadened the scope of biodiversity, with the discovery of what has been titled the “Rare Biosphere” (Sogin ''et al.'', 2006). Previous attempts to characterize in situ abundance have been made through pure culture and molecular techniques (Fuhrman, 2009). Pure culture providing a very narrow picture of some of the rarer species present, <1-5% of bacteria present (Fuhrman, 2009). Molecular techniques, such as Sanger sequencing, resulting in a much broader scope but highlighting the more abundant species present (Heidelberg et al., 2010)(Pedros-Alio, 2007). Neither technique captures all of the diversity present. Alternatively high throughput sequencing, “tag sequencing”, divides unique rRNA tag sequences into operational taxonomic units (OTUs) based upon similarities in mitochondrial-encoded cytochrome oxidases (Sogin ''et al.'', 2006). Both Sanger, shot gun sequencing, and tag sequencing organize sequences into OTUs (Heidelberg ''et al.'', 2010). However, it is the resolution that tag sequencing provides that sets it apart, resulting from the increased efficiency in serial analysis (Heidelberg ''et al.'', 2010). This efficiency increase is made possible through the use of internal primer sequences resulting in restriction-digest overhanging sequences (Heidelberg ''et al.'', 2010). Though OTUs provide a means of distinguishing the possible number of phylogenetic groups, it is not possible to deduce phylogenetic relationships based upon OTU’s. Tags associated with OTUs must be cross-referenced with gene banks, in order for tags to be phylotyped and relationships established (Sogin ''et al.'', 2006).
The result of tag sequencing has been to produce orders of magnitude larger estimates of OTUs present in ecosystems, producing a long tail on species abundance curves (Patterson, 2009)(Pedrós-Alío, 2007). This long tail accounts for less than .1% of the abundant species in a particular ecosystem. At the same time it represents thousands of populations accounting for most of the phylogenetic diversity in an ecosystem. This low-abundance high-diversity group is what is now called the “Rare Biosphere”. Using this method, Sogin et al.’s study of microbial diversity in North Atlantic deep water produced an estimate of 5266 different taxa (Sogin ''et al.'', 2006). This is particularly dramatic considering that previous studies employing more traditional PCR cloning techniques have resulted in estimates of up to 500 (Pedrós-Alío, 2007).
== Ecological role ==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Rare biosphere」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|