W Ford Doolittle

Date:
[1980]
Reference:
PP/CRI/H/6/13/5
Catalogue details

Licence: In copyright

Credit: W Ford Doolittle. Source: Wellcome Collection.

    6/23
    and the term urkaryote is at best dyseuphonious. One hopes for better terms. More serious is the objection that the organisms so far classified as archaebacteria are biochemically and ecologically very dissimilar. They comprise the obligately anaerobic methane formers, the obligately aerobic and obligately halophilic halobacteria which may show certain advanced traits [14],and two thermoacidophiles, Thermoplasma and Sul fol obus which are, aside from their thermoacidophily, dissimilar. The range of archaebacteria! metabolic modes and morphologies is as great as that shown by the eubacteria which, in the terminology of Woese and Fox, comprise most if not all other organisms described in Bergey's manual, as well as the blue-green algae (cyanobacteria), which are still considered by some to be primitive algae. The objections to such a division of the prokaryotic world were strong when its only basis was rRNA sequence data. Objections should weaken as more and more traits which distinguish the archaebacteria from the eubacteria are discovered. To date these include: distinctive tRNA modification patterns, distinctive RNA polymerases, dis tinctive antibiotic sensitivities, the absence i ri archaebacteria of peptidoglycan and the possession by them of unusual lipids, in which ether linkages replace ester linkages and isoprenoid side chains replace fatty acids [10,15,16]. The second radical conclusion derived from the data of Woese and Fox is that the nuclei of eukaryotic cells derive from a lineage, the nuclear-cytoplasmic lineage, which diverged from the eubacteria! lineage during ttie earliest stages of cellular evolution. This will be most objectionable to those who adhere to autogenous hypotheses for the origin
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