The Transcription Regulator YgeK Affects Biofilm Formation and Environmental Stress Resistance in Avian Pathogenic Escherichia coli

Abstract

Avian pathogenic Escherichia coli (APEC) is one of the most common pathogens in poultry and a potential gene source of human extraintestinal pathogenic E. coli (ExPEC), leading to serious economic losses in the poultry industry and public health concerns. Exploring the pathogenic mechanisms underpinning APEC and the identification of new targets for disease prevention and treatment are warranted. YgeK is a transcriptional regulator in APEC and is localized to the type III secretion system 2 of E. coli. In our previous work, the transcription factor ygeK significantly affected APEC flagella formation, bacterial motility, serum sensitivity, adhesion, and virulence. To further explore ygeK functions, we evaluated its influence on APEC biofilm formation and resistance to environmental stress. Our results showed that ygeK inactivation decreased biofilm formation and reduced bacterial resistance to environmental stresses, including acid and oxidative stress. In addition, the multi-level regulation of ygeK in APEC was analyzed using proteomics, and associations between differentially expressed proteins and the key targets of ygeK were investigated. Overall, we identified ygeK's new function in APEC. These have led us to better understand the transcriptional regulatory ygeK and provide new clues about the pathogenicity of APEC.

Keywords: avian pathogenic Escherichia coli; biofilm; environmental stress; transcription regulators; ygeK.

Figure 1

(A) Biofilms formed on tubes by AE81, AE81ΔygeK, and AE81ΔygeK-pCmygeK strains. (B) Measurement of biofilm mass. Values are average of three independent experiments. Error bars indicate standard deviation (*** p < 0.001).

Figure 2

Biofilm structures were observed by scanning electron microscopy (×7000 magnification).

Figure 3

Hydrogen peroxide sensitivity in AE81, AE81ΔygeK, and AE81ΔygeK-pCmygeKI strains.

Figure 4

AE81, AE81ΔygeK, and AE81ΔygeK-pCmygeK resistance to different pH values (pH = 1.0, 2.0, 3.0). Values are average of three independent experiments (* p < 0.05, ** p < 0.01, ns: no significance).

Figure 5

Differentially expressed protein volcano graph. The X-axis is the protein difference multiple (take log2) and the Y-axis is the corresponding −log10 (Q-value).

Figure 6

Up-regulated and down-regulated differentially expressed protein pathway classification.

Figure 7

Enrichment pathways show significant differentially expressed proteins.