Phytomedicine, Eidgenössische Technische Hochschule, CH-8092 Zürich, Switzerland.
EMBO J. 1989 Feb;8(2):351-8. doi: 10.1002/j.1460-2075.1989.tb03384.x.
Pseudomonas fluorescens CHA0 suppresses black root rot of tobacco, a disease caused by the fungus Thielaviopsis basicola. Strain CHA0 excretes several metabolites with antifungal properties. The importance of one such metabolite, hydrogen cyanide, was tested in a gnotobiotic system containing an artificial, iron-rich soil. A cyanidenegative (hcn) mutant, CHA5, constructed by a gene replacement technique, protected the tobacco plant less effectively than did the wild-type CHA0. Complementation of strain CHA5 by the cloned wild-type hcn genes restored the strain's ability to suppress disease. An artificial transposon carrying the hcn genes of strain CHA0 (Tnhcn) was constructed and inserted into the genome of another P.fluorescens strain, P3, which naturally does not produce cyanide and gives poor plant protection. The P3::Tnhcn derivative synthesized cyanide and exhibited an improved ability to suppress disease. All bacterial strains colonized the roots similarly and did not influence significantly the survival of T.basicola in soil. We conclude that bacterial cyanide is an important but not the only factor involved in suppression of black root rot.
荧光假单胞菌 CHA0 可抑制烟草黑胫病，该病由真菌立枯丝核菌引起。菌株 CHA0 会分泌几种具有抗真菌特性的代谢物。其中一种代谢物——氰化氢的重要性在包含人工富铁土壤的无菌体系中得到了检验。通过基因替换技术构建的氰化氢阴性（hcn）突变株 CHA5 对烟草植物的保护作用不如野生型 CHA0。通过克隆的野生型 hcn 基因对菌株 CHA5 进行互补，恢复了该菌株抑制疾病的能力。构建了一个携带菌株 CHA0 的 hcn 基因的人工转座子（Tnhcn），并将其插入天然不产生氰化物且对植物保护作用较差的另一种荧光假单胞菌菌株 P3 的基因组中。P3::Tnhcn 衍生株合成了氰化物，并表现出改善的抑制疾病的能力。所有细菌菌株都以相似的方式定殖于根际，并且对土壤中立枯丝核菌的存活没有显著影响。我们的结论是，细菌氰化物是抑制烟草黑胫病的一个重要但不是唯一因素。
