The branching order proposed by Carl Woese was based on molecular phylogeny, which was considered revolutionary as all preceding models were based on discussions of morphology. (v.Monera).[2] Several models have been proposed since and no consensus is reached at present as to the branching order of the major bacterial lineages.[3]
Despite the impact of the paper on bacterial classification, it was not a proposal for change of taxonomy. Consequently, many clades were given official names. Only subsequently, this occurred: for example, the "purple bacteria and relatives" were renamed Proteobacteria.[4]
Discussion
Atomic structure of the 30S ribosomal Subunit from Thermus thermophilus of which 16S makes up a part. Proteins are shown in blue and the single RNA strand in tan.
In 1987, Carl Woese, regarded as the forerunner of the molecular phylogeny revolution, divided Eubacteria into 11 divisions based on 16S ribosomal RNA (SSU) sequences, listed below.[1][6] Many new phyla have been proposed since then.
The root of the tree, i.e. the node of the last universal common ancestor, is placed between the domain Bacteria (or kingdom Eubacteria as it was then known) and the clade formed by the domains Archaea (formerly kingdom Archaebacteria) and Eukaryotes. This is consistent with all subsequent studies, bar the study by Thomas Cavalier-Smith in 2002 and 2004, which was not based on molecular phylogeny.[17]
Eukaryotes are a mosaic of different lineages:
The genome in the nucleus descends from the first organelle-less eukaryote, the "urkaryote" a sister species to the ancestral archeon
↑ Until recently, it was believed than only Firmicutes and Actinobacteria were Gram-positive. However, the candidate phylum TM7 may also be Gram positive.[8]Chloroflexi however possess a single bilayer, but stain negative (with some exceptions[9]).[10]
↑ Sutcliffe, I. C. (2011). "Cell envelope architecture in the Chloroflexi: A shifting frontline in a phylogenetic turf war". Environmental Microbiology. 13 (2): 279–282. doi:10.1111/j.1462-2920.2010.02339.x. PMID20860732.
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