The outer membrane protein CsgG influences biofilm formation of avian pathogenic Escherichia coli

Abstract:

[Background] Avian pathogenic Escherichia coli (APEC) could cause inflammatory conditions such as avian airsacculitis and pericarditis, which seriously restricts the healthy development of the poultry industry. Meanwhile, APEC and human extraintestinal pathogenic Escherichia coli (ExPEC) have similar virulence factors, posing a serious threat to public health. Biofilm formation can enhance the antibiotic resistance of APEC and help it escape from the host immune system. Therefore, exploring the key genes and regulatory mechanisms of the biofilm formation of APEC are of great theoretical and practical significance for the prevention and control of APEC. [Objective] To elucidate the role of the outer membrane protein CsgG in the biofilm formation of APEC, reveal the molecular mechanism of its biofilm formation, and provide a theoretical basis for the prevention and control of avian diseases associated with APEC. [Methods] The csgG-deleted strain ΔcsgG and its complementary strain CΔcsgG were constructed by Red homologous recombination. The strains were then used to study the effects of csgG on the growth, motility, membrane permeability, extracellular polysaccharide (EPS) production, and biofilm formation of APEC. [Results] The deletion of csgG did not impact the growth or membrane permeability but enhanced the motility of APEC. The deletion of csgG significantly reduced the biofilm formation of APEC. Scanning electron microscopy revealed that the biofilm changed from multilayers to monolayers after the deletion of csgG, with reduced intercellular adhesion. Confocal laser microscope revealed that the deletion of csgG led to a loose structure of the biofilm and a decrease in the number of adherent bacteria. Furthermore, the deletion of csgG significantly reduced the EPS production of APEC. The RT-qPCR results showed that the deletion of csgG led to significant reductions in the transcript levels of genes related to biofilm formation. [Conclusion] CsgG is a pivotal factor in the biofilm formation of APEC, influencing the structural integrity of the biofilm.

Key words:avian pathogenic Escherichia coli;CsgG;biofilm;extracellular polysaccharides