双组分系统rcsC基因影响禽致病性大肠杆菌的致病性及相关生物学特性

Two-component system rcsC gene affects pathogenicity and associated biological characteristics of avian pathogenic Escherichia coli

摘要:

[目的]双组分系统Rcs感受外界环境变化，并调控细菌的适应性及生存等。本文探讨Rcs双组分系统传感器激酶RcsC对禽致病性大肠杆菌（avian pathogenic Escherichia coli，APEC）相关生物学特性及致病性的影响。[方法]采用Red同源重组的方法构建rcsC基因缺失株，并利用互补质粒构建互补株，然后比较野生株、基因缺失株与互补株的生长特性、运动性、生物被膜、凝集沉淀能力、致病力及毒力基因转录水平的差异。[结果]rcsC基因缺失不影响APEC的生长速度，然而，缺失RcsC导致APEC的运动能力升高、生物被膜形成能力降低和凝集能力增强。凝集试验结果显示rcsC基因有助于APEC的凝集沉降。细胞黏附入侵结果表明，rcsC在APEC侵袭DF-1细胞过程中发挥作用，而对黏附能力无影响。动物感染试验结果表明rcsC基因缺失能显著降低APEC的毒力。荧光定量PCR检测结果表明，rcsC基因缺失株中ompA、aatA、fyuA和luxS基因的转录水平均显著降低，而fimC和tsh基因的转录水平显著升高。[结论]RcsC参与调控APEC的运动性、生物被膜形成、凝集沉降和致病力。

Abstract:

[Objective] The two-component system (TCS) Rcs is involved in the regulation of bacterial adaptation to external environment and survival. The aim of this study is to elucidate effects of sensor kinase RcsC on associated biological characteristics and virulence of avian pathogenic Escherichia coli (APEC).[Methods] We constructed the rcsC gene mutant and complementary strain of APEC by the Red recombination system and complementation plasmid. Then we compared the growth curve, motility, biofilm formation, agglutination, pathogenicity and virulence gene transcription levels of mutant, wild-type and complementary strains.[Results] rcsC gene deletion had no influence on bacterial growth. However, inactivation of rcsC gene resulted in enhanced motility, decreased biofilm formation and increased agglutination. Bacterial adherence and invasion assays showed that RcsC contribute to the invasion of APEC to DF-1 cells, whereas, it did not affect the adhesion capacity. Moreover, rcsC gene mutant strain exhibited attenuated virulence in ducks. Quantitative real-time PCR analysis demonstrated that the transcription levels of virulence genes ompA, aatA, fyuA and luxS were significantly decreased in mutant strain. Whereas, the fimC and tsh transcription levels were significantly upregulated.[Conclusion] These data indicated that RcsC play roles in regulation of bacterial motility, biofilm formation, agglutination and virulence of APEC.