摘要
原核生物幾乎無所不在，或者可說是「只要有生命的地方就有原核生物」。它們是地球上最早出現的生物體。迄今，因下述二個原因，它們仍然在生物圈佔據主導的地位：（1）原核生物總合的生物質量高於所有真核生物總生物質量達十倍之多；（2）一把肥沃土壤或人類的口腔或皮膚上的原核生物數量比存在於地球上的人類數量還多。它們可以生存於非常寒冷、非常炎熱、高鹽性、高酸性或高鹼性的環境下，它們具有多樣的適應性，使之能在許多環境下生存，同時，它們也具有高度的遺傳多樣性。難培養的植物病原原核生物為植物的病原之一，它們無法生長于目前用於培養細菌的培養基，或是需要在特定的營養或非常營養的培養基上才可生長。此類原核生物包括侷限於植物導管內的Xylella fastidiosa、Leifsonia xyIi subsp. xyli、L. xyli subsp. cynodontis、Clavibacter michiganensis subsp. sepedonicus及C. michiganensis subsp. michiganensis與侷限於韌皮部內的螺旋體、植物菌質體及柑橘黃龍病菌（Candidatus Liberibacter spp.）等。這些不易培養的植物病原菌對於植物的健康具有極大的影響。其中，X. fastidiosa可造成製酒業及生產柑橘果汁產業的巨大經濟損失。螺旋體可造成三種植物病害：柑橘頑固病、玉米矮化病及日日春的病害。植物菌質體則可造成超過500種的植物病害。而存在數十年之久的柑橘病害，黃龍病或稱柑橘立枯病，以及最近發生在馬鈴薯上的斑馬紋病及其他多種病害，皆由柑橘黃龍病菌（Ca. Liberibacter spp.）所引起。在整個美國南部地區，由德州到卡羅來納州沿著墨西哥灣沿岸直至墨西哥製酒產業都受到皮爾氏病的影響。近來曾有報導指出，褐透翅尖頭葉蟬（glassy-winged sharpshooter leafhoppers）對於加州的製酒業造成危害。自呈現柑橘斑駁黃化病徵的組織上成功的分離出X. fastidiosa及鑑定出其主要的媒介昆蟲，提供在防治柑橘斑駁黃化病上最重要的資訊，使巴西種植柑橘的農民及生產柑橘果汁的業者得以克服此病害發生時的危機。而由出現葉緣焦枯病徵的藍莓組織上成功的分離及鑑定出X. fastidiosa，繼而成功發展出抗病或耐病的藍莓栽培品系，使得喬治亞州的藍莓產業在近年來得以躍升為水果類商品第一名。
並列摘要
The prokaryotes are almost everywhere or we can phrase like this ”prokaryotes are wherever there is life”. They were the earliest organisms on earth. Today, they still dominant the biosphere for the following two facts: 1) their collective biomass outweighs all eukaryotes combined at least tenfold, and 2) more prokaryotes inhabit a handful of fertile soil or the mouth or skin of a human than the total number of people who have ever lived. They thrive in habitats that are too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote because they display diverse adaptations that allow them to inhabit many environments and they have great genetic diversity. Phytopathogenic fastidious prokaryotes are plant pathogens that either resist to grow in any available bacterial culture media or require specific or enriched media to grow. They include Xylella fastidiosa, Leifsonia xyli subsp. xyli, L. xyli subsp. cynodontis and Clavibacter michiganensis subsp. sepedonicus and C. michiganensis subsp. michiganensis that reside in xylem and spiroplasmas, phytoplasmas and Candidatus Liberibacter spp. that reside in phloem. The impacts that fastidious prokaryotes have on plant health have been enormous. Two major maladies caused by X. fastidiosa resulted in serious economic loss on wine and citrus juice industry. Three plant diseases, namely citrus stubborn, com stunt and periwinkle diseases are caused by spiroplasmas. Over 500 plant diseases were reportedly the results of phytoplasmal infestation. Ca. Liberibacter spp., are the causal agents of decades-long citrus disease called Huanglongbing or citrus greening and the recent-emerged zebra chip disease of potato and others. Pierce's disease is the limiting factor for the establishment of wine industry for the entire southeastern United States from Texas to the Carolinas along the gulf coast of Mexico. Recent introduction of the glassy-winged sharpshooter leafhoppers in California has threatened the winery industry of California. The successful isolation of X. fastidiosa from the tissues with citrus variegated chlorosis (CVC) symptoms followed by the identification of the major insect vectors provided crucial information for citrus growers and citrus juice industry to deal with the CVC crisis in Brazil. The successful isolation of X. fastidiosa from blueberry tissues with leaf scorch symptoms followed by the identification of the susceptibility/resistance of various blueberry cultivars provided significant information for the blueberry industry which has recently become the number one fruit commodity in Georgia.