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Nanobacterium (, pl. ''nanobacteria'' ) is the unit or member name of a proposed class of living organisms, specifically cell-walled microorganisms with a size much smaller than the generally accepted lower limit for life (about 200 nanometres for bacteria). Originally based on observed nano-scale structures in geological formations (including one meteorite), the status of nanobacteria has been controversial, with some researchers suggesting they are a new class of living organism capable of incorporating radiolabeled uridine,〔 and others attributing to them a simpler, abiotic nature.〔 One skeptic dubbed them "the cold fusion of microbiology", in reference to a notorious episode of supposed erroneous science.〔Jack Maniloff, quoted in "The Rise and Fall of Nanobacteria", Young and Martel, ''Scientific American'', January 2010〕 The term "calcifying nanoparticles" (CNPs) has also been used as a conservative name regarding their possible status as a life form. Research tends to agree that these structures exist, and appear to replicate in some way. However, the idea that they are living entities has now largely been discarded, and the particles are instead thought to be nonliving crystallizations of minerals and organic molecules.〔"The Rise and Fall of Nanobacteria", Young and Martel, ''Scientific American'', January 2010〕 ==1981–2000== In 1981 Torella and Morita described very small cells called ultramicrobacteria. Defined as being smaller than 300 nm, by 1982 MacDonell and Hood found that some could pass through a 200 nm membrane. Early in 1989, geologist Robert L. Folk found what he later identified as ''nannobacteria'' (written with double "n"), that is, nanoparticles isolated from geological specimens〔A convention has been adopted between researchers to name -or spell- the nanoparticles isolated from geological specimens as ''nannobacteria'', and those from biological specimens as ''nanobacteria''.〕 in travertine from hot springs of Viterbo, Italy. Initially searching for a bacterial cause for travertine deposition, scanning electron microscope examination of the mineral where no bacteria were detectable revealed extremely small objects which appeared to be biological. His first oral presentation elicited what he called "mostly a stony silence", at the 1992 Geological Society of America's annual convention. He proposed that nanobacteria are the principal agents of precipitation of all minerals and crystals on Earth formed in liquid water, that they also cause all oxidation of metals, and that they are abundant in many biological specimens.〔 In 1996, NASA scientist David McKay published a study suggesting the existence of nanofossils — fossils of Martian nanobacteria — in ALH84001, a meteorite originating from Mars and found in Antarctica. ''Nanobacterium sanguineum'' was proposed in 1998 as an explanation of certain kinds of pathologic calcification (apatite in kidney stones) by Finnish researcher Olavi Kajander and Turkish researcher Neva Ciftcioglu, working at the University of Kuopio in Finland. According to the researchers the particles self-replicated in microbiological culture, and the researchers further reported having identified DNA in these structures by staining. A paper published in 2000 by a team led by an NIH scientist John Cisar further tested these ideas. It stated that what had previously been described as "self-replication" was a form of crystalline growth. The only DNA detected in his specimens was identified as coming from the bacteria ''Phyllobacterium mysinacearum'', which is a common contaminant in PCR reactions. 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「Nanobacterium」の詳細全文を読む スポンサード リンク
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