eha基因调控迟缓爱德华菌的毒力

ehagene regulates the virulence of Edwardsiella tarda

目的 eha基因是E.tarda毒力株ET-13一个重要的转录调控基因,本文研究其对该菌株毒力的影响。方法利用菌落计数法比较野生株和eha缺失株感染小鼠毒力(LD50)的差异,以及比较两菌株在小鼠每个肝脏、脾脏和肾脏中细菌菌落数目的差异;利用组织HE染色观察两菌株对宿主组织损伤的差异;利用RT-PCR,比较两种细菌毒力基因表达的差异。结果 eha缺失株相比野生株其毒力下降了2.5倍;eha缺失株在宿主体内的生存能力明显降低。小鼠感染野生株后,出现肝细胞水肿和中性粒细胞浸润,脾小体内细胞坏死,肾小管水肿等病变,以及上述脏器外观出现改变。提示野生株对小鼠的肝脏、脾脏和肾脏有毒性作用,而eha缺失株对上述脏器无明显毒性作用。RT-PCR结果显示,eha基因的缺失使得E.tarda菌的Ⅲ型分泌系统分泌蛋白基因eseC和外膜蛋白基因(pagC)的转录水平下降,菌毛蛋白基因(fimA)的转录水平没有改变。结论 eha基因缺失后,E.tarda菌ET-13株的毒力因子表达降低,使该菌毒力明显减弱,对宿主的致病性和病理损伤减轻。因此,eha基因是一个毒力正调控基因。

The ehagene is an important transcriptive regulating gene in E.tarda virulence strain ET-13.We explored the gene for regulation of the virulence of ET-13.By comparing the differences between LD50 of the wild strain and that of theΔeha strain to mice,the LD50ofΔeha was 2.5times more than that of the wild,which indicated that the virulence of theΔeha was decreased.The numbers of theΔehastrains was significantly lower than those of the wild in a liver,a spleen and a kidney of mice post infection,which indicated that the survival viability ofΔehastrains in host in vivo decreased obviously.In order to compare the host pathological damages caused by the two kinds of strains,these tissues changes infected with the wild and theΔeha were microscopically analyzed.Results showed that the liver cells edema and neutrophil infiltration,spleen cells necrosis and edema of the renal tubules lesions occurred after the mice were infected by the wild,which indicated that the wild was toxic effects to the liver,spleen and kidney,while theΔeha wasn＇t.Results by RT-PCR showed that the transcriptional levels of T3 SS secretion protein gene C（eseC）and OMP gene（pagC）in theΔeha were significantly lower than those in the wild.Results showed that as the lower virulence factors were expressed in theΔeha,the bacterial virulence and host pathological changes were decreased significantly.Therefore,ehagene is a positive regulating gene of the virulence of E.tarda.