FTN_0109蛋白对土拉弗朗西斯菌致病力的影响

土拉弗朗西斯菌是一种重要的人畜共患性病原菌,目前对该菌的毒力因子及分子致病机制尚不完全清楚。本研究旨在分析未知功能蛋白FTN_0109在土拉弗朗西斯菌中的分布,探讨其对细菌致病力的影响。通过生物信息学软件预测FTN_0109的生物学功能,并利用超速离心法检测其亚细胞定位;利用同源重组技术构建FTN_0109基因缺失株及其反式回补株,分析其对三种来源小鼠巨噬细胞的入侵和细胞内增殖能力,并检测其对BALB/c小鼠的致病力和在其体内的繁殖动态。结果显示,FTN_0109蛋白被预测为一种脂蛋白,主要分布于土拉弗朗西斯菌的内膜;与野毒株相比,FTN_0109缺失株在小鼠巨噬细胞中不能增殖,对BALB/c小鼠的LD₅₀提高10⁴以上,在感染小鼠肝和脾中的载量呈不断下降趋势且均显著低于野毒株（P<0.05）。结果提示,FTN_0109是一种内膜脂蛋白,它的缺失可严重降低土拉弗朗西斯菌在小鼠巨噬细胞和体内的生存能力,降低其对小鼠的致病力。

The Effect of the Protein FTN_0109 on the Virulence of Francisella tularensis

Francisella tularensis (F. tularensis) is an important zoonotic pathogen, but its virulence factors and molecular pathogenesis are still unclear. This study aimed to analyze the distribution of unknown functional protein FTN_0109 in F. tularensis, and to explore its influence on the virulence of F.tularensis. The biological function of FTN_0109 was predicted by bioinformatics softwares and its subcellular localization was detected by hypervelocity centrifugation. The FTN_0109 gene deleted strain and its trans-complemented strain were constructed by homologous recombination method. The invasion and intracellular proliferation ability of the wild-type strain and its derivates in three macrophagocytes from mice were detected, and their pathogenicity and proliferation dynamics in BALB/c mice were analyzed. The results showed that FTN_0109 was predicted to be a kind of lipoprotein, mainly distributed in the inner membrane of F. tularensis. FTN_0109 mutant strain could not proliferate in mouse macrophages and its LD₅₀ in BALB/c mice increased more than 10⁴ CFU compared with wild-type strain. The bacterial load of FTN_0109 mutant strain in infected mice showed a decreasing trend and was significantly lower than that of wild-type strain(P<0.05). The results suggested that FTN_0109 was an inner membrane lipoprotein, and its deletion could seriously reduce the survival ability of F. tularensis in macrophages and mice, and thus reduced its pathogenicity in mice.