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''Pseudomonas'' is a genus of Gram-negative, aerobic gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species. The members of the genus demonstrate a great deal of metabolic diversity, and consequently are able to colonize a wide range of niches. Their ease of culture ''in vitro'' and availability of an increasing number of ''Pseudomonas'' strain genome sequences has made the genus an excellent focus for scientific research; the best studied species include ''P. aeruginosa'' in its role as an opportunistic human pathogen, the plant pathogen ''P. syringae'', the soil bacterium ''P. putida'', and the plant growth-promoting ''P. fluorescens''. Because of their widespread occurrence in water and plant seeds such as dicots, the pseudomonads were observed early in the history of microbiology. The generic name ''Pseudomonas'' created for these organisms was defined in rather vague terms by Walter Migula in 1894 and 1900 as a genus of Gram-negative, rod-shaped and polar-flagellated bacteria with some sporulating species,〔Migula, W. (1894) Über ein neues System der Bakterien. Arb Bakteriol Inst Karlsruhe 1: 235–328.〕〔Migula, W. (1900) System der Bakterien, Vol. 2. Jena, Germany: Gustav Fischer.〕 the latter statement was later proved incorrect and was due to refractive granules of reserve materials. Despite the vague description, the type species, ''Pseudomonas pyocyanea'' (basonym of ''Pseudomonas aeruginosa''), proved the best descriptor.〔 == Classification history == Like most bacterial genera, the pseudomonad〔 last common ancestor lived hundreds of millions of years ago. They were initially classified at the end of the 19th century when first identified by Walter Migula. The etymology of the name was not specified at the time and first appeared in the seventh edition of ''Bergey's Manual of Systematic Bacteriology'' (the main authority in bacterial nomenclature) as Greek ''pseudes ''(ψευδής) "false" and ''-monas'' (μονάς/μονάδος) "a single unit", which can mean false unit; however, Migula possibly intended it as false ''Monas'', a nanoflagellated protist〔 (subsequently, the term "monad" was used in the early history of microbiology to denote unicellular organisms). Soon, other species matching Migula's somewhat vague original description were isolated from many natural niches and, at the time, many were assigned to the genus. However, many strains have since been reclassified, based on more recent methodology and use of approaches involving studies of conservative macromolecules. Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus ''Pseudomonas'' includes strains formerly classified in the genera ''Chryseomonas'' and ''Flavimonas''. Other strains previously classified in the genus ''Pseudomonas'' are now classified in the genera ''Burkholderia'' and ''Ralstonia''. In 2000, the complete genome sequence of a ''Pseudomonas'' species was determined; more recently, the sequence of other strains has been determined, including ''P. aeruginosa'' strains PAO1 (2000), ''P. putida'' KT2440 (2002), ''P. protegens'' Pf-5 (2005), ''P. syringae'' pathovar tomato DC3000 (2003), ''P. syringae'' pathovar syringae B728a (2005), ''P. syringae'' pathovar phaseolica 1448A (2005), ''P. fluorescens'' Pf0-1, and ''P. entomophila'' L48.〔 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「Pseudomonas」の詳細全文を読む スポンサード リンク
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