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The bacterial phyla are the major lineages (phyla or divisions) of the domain ''Bacteria''. In the scientific classification established by Carl von Linné, each bacterial strain has to be assigned to a species (binary nomenclature), which is a lower level of a hierarchy of ranks. Currently, the most accepted mega-classification system is under the three-domain system, which is based on molecular phylogeny. In that system, bacteria are members of the domain ''Bacteria''〔 and "phylum" is the rank below domain as the rank "kingdom" is disused at present in bacterial taxonomy.〔 In this classification scheme, ''Bacteria'' is (unofficially)〔 subdivided into over 29 phyla with representatives cultured in a lab.〔〔 Many major clades of bacteria that exist but cannot currently be cultured are known solely via metagenomics and are called candidate phyla. If these are included, the number of phyla is 52 or higher. Therefore, the number of major phyla has increased from 12 identifiable lineages in 1987, to 52 .〔 Regarding the precise phylogeny at the base of the clade Bacteria, some scientists believe there may be a branching order, whereas other scientists, such as Norman Pace, believe the various Bacterial phyla represent a large hard polytomy (a simultaneous multiple speciation event). ==Molecular phylogenetics== Traditionally, phylogeny were inferred and taxonomy established based on studies of morphology. Recently molecular phylogenetics has been used to allow better elucidation of the evolutionary relationship of the species by analysing their DNA/protein sequences, for example their ribosomal DNA. The lack of easily accessible morphological features, such as those present in animals and plants, hampered early efforts of classification and resulted in erroneous, distorted and confused classification, an examples of which, noted Carl Woese, is ''Pseudomonas'' whose etymology ironically matched its taxonomy, namely "false unit".〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bacterial phyla」の詳細全文を読む スポンサード リンク
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