氧化葡萄糖酸杆菌通过降低pH值损害斑翅果蝇及益生菌

Pathogenicity of Gluconobacter oxydans toward Drosophila suzukii and probiotics by reducing pH

摘要:

【目的】分离斑翅果蝇病原性细菌并解析其致病机理,以期应用于生物防治斑翅果蝇。【方法】利用平板划线的方法,从已发生褐变的斑翅果蝇培养物中分离引起褐变的细菌,并通过16S rRNA基因序列进行鉴定;使用酸化乙醇法测定褐变物质,检测细菌的褐变能力;在致病性检测实验中,利用菌液饲喂法检测病原菌对果蝇存活率的影响,使用二氢乙锭(dihydroethidium, DHE)染色法检测肠道活性氧(reactive oxygen species, ROS)活性,用亮蓝染色检测肠道通透性。【结果】从斑翅果蝇培养物中分离出褐变性细菌氧化葡萄糖酸杆菌(Gluconobacter oxydans)。该菌株显著地降低斑翅果蝇存活率,第8天时存活率下降到49.41% (P<0.001);同时,该菌株显著地降低斑翅果蝇对缺水和饥饿等胁迫耐受性(P<0.001),分别在第24小时和第32小时存活率降到58%和50.9%。G. oxydans感染损伤果蝇肠道通透性并显著地增高ROS水平(P<0.001)。G. oxydans强烈地降低斑翅果蝇培养基pH值(pH 2.0),进而降低果蝇存活率、抑制和灭杀益生菌植物乳杆菌(Lactobacillus plantarum)。【结论】G. oxydans通过强烈降低培养基pH而降低斑翅果蝇存活率,同时可抑制益生菌生长,表明该菌具有较好的防治斑翅果蝇等害虫的潜能。

Abstract:

【Objective】 To isolate the pathogenic bacteria of Drosophila suzukii and study the mechanism of bacterial pathogenicity towards the host. 【Methods】 The pathogenic bacteria were isolated by the plate streaking method and identified based on the 16S rRNA gene sequences. The acidified ethanol method was employed to measure the ability of the isolate to cause browning. The pathogenicity of the isolate was examined by oral infection. Dihydroethidium (DHE) was used to determine the level of reactive oxygen species (ROS), and brilliant blue staining was used to examine the intestinal permeability. 【Results】 A strain was isolated from the brown culture medium of D. suzukii and identified as Gluconobacter oxydans. The strain reduced the survival rate of D. suzukii to 49.41% on day 8 (P<0.001). Furthermore, it weakened the tolerance of D. suzukii to desiccation and starvation, reducing the survival rate to 58% and 50.9% at the time points of 24 h and 32 h, respectively (P<0.001). Moreover, the flies treated with G. oxydans displayed impaired integrity of the intestine and had higher level of ROS in the guts than the control group (P<0.001). G. oxydans robustly reduced the medium pH (pH 2.0), which compromised the survival rate of D. suzukii and the growth of Lactobacillus plantarum, a probiotic of D. suzukii. 【Conclusion】 G. oxydans was a potent pathogen capable of reducing the survival rate of D. suzukii by lowering the medium pH and inhibiting the growth of probiotics, demonstrating the potential of serving the biocontrol of D. suzukii.