以N-乙酰高丝氨酸内酯(N-acyl-homoserine lactone,AHL)为信号分子的群体感应(quorum-sensing,QS)系统是很多病原细菌的重要致病性调控因子。本文自甜瓜果斑病菌——西瓜食酸菌(Acidovorax citrulli)菌株MH21中克隆到AHL信号合成基因luxIMH21,并构建了其缺失突变体MΔluxIMH21及转化有AHL信号降解酶编码基因aiiA和aidH的工程菌株MAiiA和MAidH。信号检测结果显示MΔluxIMH21、MAiiA和MAidH菌株均无AHL信号产生,同时细菌的游动能力及在基本培养基中的生长速率均显著下降,但对细菌生物膜形成和在非寄主植物烟草上诱导过敏性坏死反应的能力没有影响。盆栽条件下,经低浓度(104CFU/mL)MΔluxIMH21、MAiiA和MAidH菌株处理的甜瓜种子萌发后幼苗死亡率显著低于野生型MH21和lux-IMH21基因互补菌株MΔluxIMH21HB的处理;而高浓度细菌(108CFU/mL)处理种子后,除MAidH菌株处理引起的死苗率明显低于野生型MH21处理,其他菌株与MH21没有显著差异。子叶注射试验也得到相似的结果,以低浓度细菌(104CFU/mL)注射甜瓜子叶后发现MΔluxIMH21、MAiiA和MAidH菌株甜瓜子叶中的繁殖速率及对子叶的致病力与野生型MH21相比均显著下降;而高浓度细菌(108CFU/mL)处理子叶时,MΔluxIMH21和MAiiA菌株与野生菌MH21相比致病力无显著差异,仅有MAidH菌株的致病力明显下降。说明QS系统影响菌株MH21在低细菌浓度下对甜瓜幼苗的致病力,这种作用可能与影响细菌生长有关。 The quorum-sensing (QS) system using N-acyl-homoserine lactone (AHL) as a signaling molecule is an important pathogenic regulator of many pathogenic bacteria. In this paper, AHL signal synthesis gene luxIMH21 was cloned from Acidovorax citrulli strain MH21, and its deletion mutant MΔluxIMH21 and the project of transformation of aiiA and aidH transformed with AHL signal degrading enzyme Strain MAiiA and MAidH. The results of signal test showed that no AHL signal was produced in MΔluxIMH21, MAiiA and MAidH strains, while the ability of bacteria to swim and the growth rate in minimal medium were significantly decreased, but the biofilm formation and induction of allergy on non-host tobacco The ability of a sexual necrosis reaction has no effect. Under potted condition, the seedling mortality of melon seeds treated with MΔluxIMH21, MAiiA and MAidH strains at low concentrations (104CFU / mL) was significantly lower than that of MΔluxIMH21HB with wild-type MH21 and lux-IMH21 genes; while the high concentration of bacteria (108CFU / mL), the rate of dead seedlings caused by the treatment of MAidH strain was significantly lower than that of wild-type MH21 treatment, and no significant difference was found between the other strains and MH21. Similar results were obtained with cotyledon injection test. The results showed that the rate of reproduction of melon cotyledons and the virulence of cotyledon of MΔluxIMH21, MAiiA and MAidH strains were significantly higher than that of wild-type MH21 after injecting cotyledons with low concentration of bacteria (104CFU / mL) , While the pathogenicity of MΔluxIMH21 and MAiiA strains was not significantly different from that of wild-type strain MH21. However, only the pathogenicity of MAidH strain was significantly decreased when the cotyledons were treated with high concentration of bacteria (108CFU / mL). The results showed that the QS system affected the pathogenicity of strain MH21 to melon seedlings at low bacterial concentrations, which may be related to the growth of bacteria.