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L-form bacteria, also known as L-phase bacteria, L-phase variants, and cell wall-deficient (CWD) bacteria, are strains of bacteria that lack cell walls. They were first isolated in 1935 by Emmy Klieneberger-Nobel, who named them "L-forms" after the Lister Institute in London where she was working. Two types of L-forms are distinguished: ''unstable L-forms'', spheroplasts that are capable of dividing, but can revert to the original morphology, and ''stable L-forms'', L-forms that are unable to revert to the original bacteria. Some parasitic species of bacteria, such as mycoplasma, also lack a cell wall, but these are not considered L-forms since they are not derived from bacteria that normally have cell walls.〔 (Full PDF )〕 ==Appearance and cell division== Bacterial morphology is determined by the cell wall. Since the L-form has no cell wall, its morphology is different from that of the strain of bacteria from which it is derived. Typical L-form cells are spheres or spheroids. For example, L-forms of the rod-shaped bacterium ''Bacillus subtilis'' appear round when viewed by phase contrast microscopy or by transmission electron microscopy. Although L-forms can develop from Gram-positive as well as from Gram-negative bacteria, in a Gram stain test, the L-forms always colour Gram-negative, due to the lack of a cell wall. The cell wall is important for cell division, which, in most bacteria, occurs by binary fission. This process usually requires a cell wall and components of the bacterial cytoskeleton such as FtsZ. The ability of L-form bacteria to grow and divide in the absence of both of these structures is highly unusual, and may represent a form of cell division that was important in early forms of life.〔 This novel mode of division seems to involve the extension of thin protrusions from the cell's surface and these protrusions then pinching off to form new cells. The lack of cell wall in L-forms means that division is disorganised, giving rise to a variety of cell sizes, from very tiny to very big. 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「L-form bacteria」の詳細全文を読む スポンサード リンク
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