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木质部存在的细菌(Xylem-Limited Bacteria—XLB)是指那些用常规的细菌学方法难于分离的原核生物病原物。这些难养生物需要复杂的培养基以供生长,它们仅存在于受侵染植物的木质部,由取食木树质部的叶蝉类传播,引致许多重要经济作物发生难以控制的病害。这类病害最初被发现时由于其超微结构与动物的立克次氏体相似,所以被称作类立克次细菌(Rickettsia like bacteria);近年来,许多XLB已离体培养成功并证实了其致病性。细菌(XLB)的纯培养物已应用于研究菌体中的鸟嘌吟+胞嘧啶(G+C)含量比及与其它植物病原细菌和立克次体的血清学关系。现已证实,XLB与动物的立克次体以及其他植物病原物无关。
Xylem-Limited Bacteria-XLB refers to prokaryotic pathogens that are difficult to isolate by conventional bacteriological methods. These difficult-to-live organisms require complex media for growth. They exist only in the xylem of infected plants and are spread by leafhoppers that feed on the xylem, causing unmanageable diseases in many important cash crops. Such diseases were first identified as Rickettsia-like bacteria due to their ultrastructure similar to that of animals; in recent years many XLBs have been successfully cultured in vitro and confirmed Its pathogenicity. Pure cultures of bacteria (XLB) have been used to study the ratio of guanine + cytosine (G + C) content in bacteria and their serological relationships with other plant pathogenic bacteria and rickettsia. It has been confirmed that XLB has nothing to do with the rickettsia of animals and other plant pathogens.