Archaea – Wikipedia tiếng Việt

# Archaea

### Bách khoa toàn thư mở Wikipedia

Archaea
Phân loại khoa học

Giới (Kingdom): | Archaea Woese, Kandler & Wheelis, 1990

Phyla / Classes

Phylum Crenarchaeota
Phylum Euryarchaeota
Halobacteria
Methanobacteria
Methanococci
Methanopyri
Archaeoglobi
Thermoplasmata
Thermococci
Phylum Korarchaeota
Phylum Nanoarchaeota

Archaea (tiếng Latinh, tức là "cổ đại"; đôi khi được dịch trong tiếng Việt là vi khuẩn cổ) là một phân nhóm lớn trong prokaryote (bên cạnh vi khuẩn). Archeae là một phân ngành chính của những sinh vật sống. Mặc dù chưa có sự chắc chắn nào về sự hình thành lòai. Archeae(vi khuẩn cổ), Eukaryote(đa bào) và Bacteria (vi khuẩn)là những phân nhóm cơ bản,trong cái được gọi là hệ thống 3 nghành chính. Giống nhu Bacteria,archeae là những sinh vật đơn bào thiếu nhân(nuclei), do đó chúng là đơn bào. Ban đầu người ta tìm thấy chúng ở nhưng môi trường sống khắc nghiệt, nhưng sau này người ta tìm thấy chúng ở hầu hết những mọi môi trường sống. Về vị trí phân loại của những sinh vật này có nhiều điểm chưa thống nhất vì chúng có những đặc điểm giống với vi khuẩn nhưng cũng mang nhiều đặc điểm của eukaryote.

Bài này đang được dịch từ tiếng Anh. Nếu bạn có đủ khả năng xin góp sức dịch bài này. (Xin tham khảo Hướng dẫn cách biên soạn bài để biết thêm chi tiết.) Nếu không tiếp tục được quan tâm phần ngoại ngữ của bài sẽ bị xoá sau khoảng 1 tháng.

## [sửa] Lịch sử

They were identified in 1977 by Carl Woese and George Fox based on their separation from other prokaryotes on 16S rRNA phylogenetic trees. These two groups were originally named the Archaebacteria and Eubacteria, treated as kingdoms or subkingdoms. Woese argued that they represented fundamentally different branches of living things. He later renamed the groups Archaea and Bacteria to emphasize this, and argued that together with Eukarya they comprise three domains of living things.

## [sửa] Archaea, vi khuẩn, và eukaryote

Archaea are similar to other prokaryotes in most aspects of cell structure and metabolism. However, their genetic transcription and translation - the two central processes in molecular biology - do not show the typical bacterial features, but are extremely similar to those of eukaryotes. For instance, archaean translation uses eukaryotic initiation and elongation factors, and their transcription involves TATA-binding proteins and TFIIB as in eukaryotes.

Several other characteristics also set the Archaea apart. Unlike most bacteria, they have a single cell membrane that lacks a peptidoglycan wall. Further, both bacteria and eukaryotes have membranes composed mainly of glycerol-ester lipids, whereas archaea have membranes composed of glycerol-ether lipids. These differences may be an adaptation on the part of Archaea to hyperthermophily. Archaeans also have flagella that are notably different in composition and development from the superficially similar flagella of bacteria.

A phylogenetic tree based on rRNA data, showing the separation of bacteria, archaea, and eukaryotes.

## [sửa] Habitats

Many archaeans are extremophiles. Some live at very high temperatures, often above 100°C, as found in geysers and black smokers. Others are found in very cold habitats or in highly saline, acidic, or alkaline water. However, other archaeans are mesophiles, and have been found in environments like marshland, sewage, and soil. Many methanogenic archaea are found in the digestive tracts of animals such as ruminants, termites, and humans. Archaea are usually harmless to other organisms and none are known to cause disease.

## [sửa] Form

Individual archaeans range from 0.1 to over 15 μm in diameter, and some form aggregates or filaments up to 200 μm in length. They occur in various shapes, such as spherical, rod-shaped, spiral, lobed, or rectangular. They also exhibit a variety of different types of metabolism. Of note, the halobacteria can use light to produce ATP, although no Archaea conduct photosynthesis with an electron transport chain, as occurs in other groups.

## [sửa] Evolution and classification

Archaea are divided into two main groups based on rRNA trees, the Euryarchaeota and Crenarchaeota. Two other groups have been tentatively created for certain environmental samples and the peculiar species Nanoarchaeum equitans, discovered in 2002 by Karl Stetter, but their affinities are uncertain.

Woese argued that the bacteria, archaea, and eukaryotes each represent a primary line of descent that diverged early on from an ancestral progenote with poorly developed genetic machinery. This hypothesis is reflected in the name Archaea, from the Greek archae or ancient. Later he treated these groups formally as domains, each comprising several kingdoms. This division has become very popular, although the idea of the progenote itself is not generally supported. Some biologists, however, have argued that the archaebacteria and eukaryotes arose from specialized eubacteria.

The relationship between Archaea and Eukarya remains an important problem. Aside from the similarities noted above, many genetic trees group the two together. Some place eukaryotes closer to Eurarchaeota than Crenarchaeota are, although the membrane chemistry suggests otherwise. However, the discovery of archaean-like genes in certain bacteria, such as Thermotoga, makes their relationship difficult to determine. Some have suggested that eukaryotes arose through fusion of an archaean and eubacterium, which became the nucleus and cytoplasm, which accounts for various genetic similarities but runs into difficulties explaining cell structure.

Single gene sequencing for systematics has led to whole genome sequencing, currently 22 archaeal genomes have been completed with 15 partially completed [1].

## [sửa] Tham khảo

- Howland, John L. (2000). The Surprising Archaea: Discovering Another Domain of Life. Oxford: Oxford University Press. ISBN 0-19-511183-4.
- Lake, J.A. (1988). "Origin of the eukaryotic nucleus determined by rate-invariant analysis of rRNA sequences". Nature 331:184–186.
- Woese, Carl R.; Fox, George E. (1977). "Phylogenetic Structure of the Prokaryotic Domain: The Primary Kingdoms". Proceedings of the National Academy of Sciences of the United States of America 74 (11): 5088–5090.
- Woese, Carl R., Kandler, Otto, Wheelis, Mark L (1990). "Towards a natural system of organisms: Proposal for the domains Archaea, Bacteria, and Eucarya". Proceedings of the National Academy of Sciences 87 (12): 4576–4579.

## [sửa] Liên kết ngoài

- Archaea
- ArchaeaWeb - by UNSW - Information about Archaea
- Introduction to the Archaea, ecology, systematics and morphology
- Extremophiles Bioprospecting for antimicrobials, Dr Sarah Maloney Citat: "...Ground breaking research on extremophiles continues to this day, with the recently discovered 22nd genetically encoded amino acid – pyrrolysine – from the archaeon, Methanosarcina barkeri, (Hao et al., 2002; Srinivasan et al., 2002)...."
- BBC News July 21, 1999: Toughest bug reveals genetic secrets Citat: "...It [Pyrococcus abyssi] likes conditions that the vast majority of other organisms would find impossible to live in. It thrives best at temperatures of about 103 degrees [Celsius] and under pressures of about 200 atmospheres...."
- Pyrococcus abyssi Home page at Genoscope

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Thể loại: Bài đang dịch Sinh học | Archaea | Extremophiles | Sinh vật

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