Effect of ygeG on biological characteristics and the pathogenicity of avian pathogenic Escherichia coli

Abstract:

[Objective] To construct the ygeG deletion strain of avian pathogenic Escherichia coli (APEC), and analyze its biological characteristics and pathogenicity to explore the role of ygeG plays on the pathogenesis of APEC, so as to lay a foundation for further research on the pathogenesis of type three secretion system 2 (ETT2), which ygeG locates in.[Methods] The ygeG deletion strain (APEC81-ΔygeG) and complementary strain (APEC81-CΔygeG) were constructed by Red homologous recombination technology. Then, the growth curve, motility, biofilm formation, stress resistance, serum resistance among APEC81, APEC81-ΔygeG and APEC81-CΔygeG were compared and analyzed. The effect on host infection of ygeG was investigated by cell adhesion, invasion test and inflammatory factor expression level detection by fluorescence quantitative PCR.[Results] We successfully constructed APEC81-ΔygeG and APEC81-CΔygeG. Compared with APEC81, there was no significant changes in growth characteristics in APEC81-CΔygeG (P>0.05). However, biofilm formation ability of APEC81-ΔygeG significantly decreased (P<0.01), motility of APEC81-ΔygeG extremely significantly improved (P<0.001). Compared with APEC81, APEC81-ΔygeG showed lower tolerance to acid (P<0.001) and oxidative shock (P<0.001), and higer tolerance to alkali (P<0.01), osmotic pressur (P<0.01) and heat shock (P<0.01). Furthermore, serum survival experiments results showed that deletion of ygeG significantly decreased survival abilities of APEC81 in serum (P<0.01), and extremely significantly decreased at serum concentrations of 100% and 30% (P<0.001); The adhesion of APEC81-ΔygeG to epithelial cells of chicken trachea mucosa was extremely significantly decreased (P<0.001), and the invasion ability was significantly increased (P<0.01). Furthermore, qPCR results also showed that APEC81-ΔygeG significantly up-regulated the transcription level of of inflammatory factors in chicken tracheal epithelial cells (P<0.01).[Conclusion] These data indicated that ygeG plays roles in regulation of biofilm formation, motility, stress resistance, adhesion and invasion ability, and serum resistance of APEC, it also can inhibit cell inflammatory factor expression.