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''Pseudomonas syringae'' is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to researchers from international culture collections such as the NCPPB, ICMP, and others. It is unclear whether these pathovars represent a single species. ''P. syringae'' is a member of the ''Pseudomonas'' genus, and based on 16S rRNA analysis, it has been placed in the ''P. syringae'' group. It is named after the lilac tree (''Syringa vulgaris''), from which it was first isolated. ''P. syringae'' tests negative for arginine dihydrolase and oxidase activity, and forms the polymer levan on sucrose nutrient agar. Many, but not all, strains secrete the lipodepsinonapeptide plant toxin syringomycin, and it owes its yellow fluorescent appearance when cultured ''in vitro'' on King's B medium to production of the siderophore pyoverdin. ''P. syringae'' also produces Ina proteins which cause water to freeze at fairly high temperatures (-4 °C to -2 °C), resulting in injury to plants. Since the 1970s, ''P. syringae'' has been implicated as an atmospheric "biological ice nucleator", with airborne bacteria serving as cloud condensation nuclei. Recent evidence has suggested the species plays a larger role than previously thought in producing rain and snow. They have also been found in the cores of hailstones, aiding in bioprecipitation. These Ina proteins are also used in making artificial snow. ''P. syringae'' pathogenesis is dependent on effector proteins secreted into the plant cell by the bacterial type III secretion system. Nearly 60 different type III effector families encoded by ''hop'' genes have been identified in ''P. syringae''.〔http://pseudomonas-syringae.org/〕 Type III effectors contribute to pathogenesis chiefly through their role in suppressing plant defense. Owing to early availability of the genome sequence for three ''P. syringae'' strains and the ability of selected strains to cause disease on well-characterized host plants, including ''Arabidopsis thaliana'', ''Nicotiana benthamiana'', and tomato, ''P. syringae'' has come to represent an important model system for experimental characterization of the molecular dynamics of plant-pathogen interactions. ==Epidemiology== Disease by ''P. syringae'' tends to be favoured by wet, cool conditions—optimum temperatures for disease tend to be around 12–25 °C, although this can vary according to the pathovar involved. The bacteria tend to be seed-borne, and are dispersed between plants by rain splash. Although it is a plant pathogen, it can also live as a saprotroph in the phyllosphere when conditions are not favourable for disease. Some saprotrophic strains of ''P. syringae'' have been used as biocontrol agents against postharvest rots. 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 syringae」の詳細全文を読む スポンサード リンク
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