Are archaea and archaebacteria the same thing?


Registration date: 11/06/2004
Posts: 2344
Place of residence: Hessen
Posted: Oct 31, 2011 5:13 PM Subject:

It's actually described quite well here in the wiki article:

The separate position of the archaea as an independent domain is due to clear differences in the sequence of the RNA contained in the ribosomes, namely the small ribosomal subunit (16S rRNA), and other genetic, physiological, structural and biochemical properties. [...]

Archaea are more similar to eukaryotes than bacteria in many molecular biological properties. Nevertheless, they have typical bacterial properties, e.g. B. the cell size, the lack of a cell nucleus, the type of cell division, they have a self-contained DNA molecule, also relatively simply structured locomotion organs (flagella) and, like bacteria, ribosomes with the sedimentation coefficient 70S (although the archaeal ribosomes are more complex in their structure). The genes of both domains are organized in so-called operons. Archaea can also carry plasmids, such as an archaeon of the Crenarchaeota genus Sulfolobus. [2]

The central molecular processes, for example translation and transcription, on the other hand, are quite similar to those of the eukaryotes: Archaea use similar RNA polymerases (rifampicin and streptolydigin-resistant) composed of several protein subunits; very similar initiation and elongation factors occur during translation, the start of transcription is marked by a so-called TATA box.

However, the archaea also have many unique properties, especially the structure of the cell wall shows clear differences to the other domains: The archaeal cell walls contain pseudopeptidoglycan (pseudomurein) and are generally very diverse in their structure: some archaea completely lack a cell wall (thermoplasm), others have highly complex cell walls consisting of many layers (methanospirillum). Due to the different structure, archaea are generally resistant to cell wall antibiotics. The composition of the archaeal plasma membrane also differs: in bacteria and eukaryotes, fatty acids are bound to the glycerol molecules via an ester bond, in archaea one can find glycerol diethers or even bis-glycerol tetraethers (single-layer membrane, monolayer) and branched isoprene Units instead of simple fatty acids. Hyperthermophilic archaea often have more stable, single-layer membranes (glycerol tetraether [3]). [Status: 31.10.2011]
(Emphasis mine)
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