Effect of ETT2 transcriptional regulator EtrA on the pathogenicity of avian pathogenic Escherichia coli

Abstract:

[Background] Avian pathogenic Escherichia coli (APEC) is one of the main pathogens of poultry. ETT2 (Escherichia coli type III secretion system 2) regulates its pathogenicity through transcriptional regulators. Currently, the effect of the transcriptional regulators EtrA on its pathogenicity in APEC is unclear. [Objective] To study the effect of ETT2 transcriptional regulator EtrA on the pathogenicity of APEC. [Methods] APEC40-ΔetrA and APEC40-CΔetrA were constructed by the lambda Red recombinase system. Then the biological characteristics, including growth characteristics, biofilm formation ability, motility and sensitivity to serum was compared between APEC40 and APEC40-ΔetrA. Besides, the transcriptional levels of virulence genes, biofilm formation related genes and flagellin synthesis genes of wild and complementation strain were compared by RNA-Seq and real-time PCR. [Results] The growth characteristics did not significantly change between APEC40 and APEC40-ΔetrA (P>0.05). However, the biofilm formation and sensitivity to serum were significantly enhanced (P<0.001), while the motility was significantly decreased (P<0.01) compared with the wild strain APEC40. There was some recovery in the phenotype of the complemented strains. Furthermore, transcriptomics screened seven virulence difference genes, which showed that the genes related to biofilm formation were significantly up-regulated, and the genes involved in motility were significantly down-regulated. The results of qRT-PCR were consistent with those of RNA-Seq. [Conclusion] Loss of etrA can significantly affect the biofilm formation, motility, and sensitivity to serum in APEC. This study provides a reference for further study on the pathogenicity of ETT2 in APEC.