Influence of Heterologously Expressed azurin from Pseudomonas aeruginosa on the Adhesion and Invasion of Pathogenic Bacteria to the Caco-2 Cell Line

This study proposed to investigate the effect of azurin on the major stages of pathogenesis (adhesion and invasion) of intestinal bacterial pathogens (Salmonella spp. and Escherichia coli) and epithelial pathogens (Staphylococcus aureus and Pseudomonas aeruginosa) on the human colorectal adenocarcinoma (Caco-2) cell line. Azurin protein was produced by cloning the azurin gene into pET21a and heterologous expression in E. coli BL21. The protein was purified using affinity chromatography and confirmed by Western blotting. The purified protein was evaluated by three experiments of adhesion and invasion assays, including exclusion, competition, and replacement. Azurin was observed to significantly inhibit the attachment and invasion of S. aureus, Salmonella spp., and E. coli, while no such inhibitory effects were observed on P. aeruginosa. In fact, the protein increased the adhesion of P. aeruginosa to the cell. In conclusion, our study proposes that azurin is a potential prophylactic or preventive helper candidate to inhibit the attachment and invasion of pathogenic bacteria to host cells and reduce the progression of the infection process. Our study also reveals the involvement of azurin in bacteria-host cell interactions, providing novel and important insights toward the elucidation of its biological function in this field. Thus, this study provides new opportunities to use azurin as an adjunct therapy against critical stages of infection by a wide range of pathogenic bacteria.