Essay on Archaea VS Bacteria

2381 Words May 7th, 2015 10 Pages
Should Bacteria and Archaea belong to the same Kingdom?

The main purpose of this essay is to find out if Archaea and Bacteria should be classified as two different Kingdoms or as a single one. As organisms, bacteria and archaea both are microscopic and prokaryotic (not possessing a true nucleus). These prokaryotes are very abundant on Earth and inhabit a wide spread of areas, including extreme ones. Both are an example of the most ancient living cells, which have appeared over 3.5 billion years ago. Correct classification of these organisms is important in order to trace the evolutionary history from the very beginning and make a clearer picture of the common ancestor, if it existed. This work will explain the basic taxonomy
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All living organisms have got plasma membranes of a similar structure. Normally, they are made of phospholipids – a glycerol attached to a hydrophylic phosphate head and two hydrophylic lipid "tails" building up a phospholipid bilayer (Alberts, 2014). Bacterial phospholipids are made with the help or ester bonds and include oxygen atoms, double-bonded to carbon atoms. Archaeal phospholipids feature ether bonds instead, lacking the C=O double bond, and featuring some methyl groups (branching) on the fatty acids (De Rosa 1986), see Figure 2.

Figure 2: Phospholipid structure in archaea (top) and bacteria (bottom), acquired from: www.ucmp.berkeley.edu

Talking about motility, some prokaryotes use flagella in order to move around. They are completely different from those found in eukaryotes and look more like a boat motor – featuring rings of flagellin – protein able to perform spinning propeller-like motion, powered up by electron transport chain and hydrogen ion movement (Brooker, 2014). The outer long filament is connected with the flagellin structure by a hook. Both archaeal and bacterial flagella are similar in appearance and function. However, recent analysis revealed some differences. Kato (2011) reports some of them, for example, flagella of archaea are two times thinner than bacterial (10-12 nm against 18-22 nm). The "motor" structure is
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