Functional Analysis of Fis in Aeromonas Veronii TH0426 Reveals a Key Role in the Regulation of Virulence and Adhesion

Abstract

Background: Aeromonas veronii is a comorbid pathogen that can infect humans, animals, and various aquatic animals. In recent years, an increasing number of cases of A. veronii infection have been reported, and its virulence and drug resistance have also been increasing gradually, indicating serious risks. This bacterium not only threatens public health and safety but also causes considerable economic loss in the aquaculture industry; however, little is known about its pathogenic mechanism.Results: In this study, we first constructed the A. veronii TH0426 Fis gene deletion strain ΔFis and the complementation strain C-Fis through homologous recombination technology. The results showed that the adhesion and invasion ability of the ΔFis deletion strain towards Epithelioma papulosum cyprini (EPC) cells and the cytotoxicity were 3.8-fold and 1.3-fold lower, respectively, than those of the wild-type strain. The animal pathogenicity of ΔFis was 2.9-fold lower than that of the wild-type strain. In addition, the bacterial load of the deletion strain ∆Fis in crucian carp was significantly lower than that of the wild-type strain, and the load decreased with time. In summary, deletion of the Fis gene led to a decrease in the virulence of A. veronii.Conclusions: Our research results show that the deletion of the Fis gene significantly reduces the virulence and adhesion ability of A. veronii TH0426. Therefore, the Fis gene plays a vital role in the pathogenesis of TH0426. This preliminary study of the function of the Fis gene in A. veronii will help researchers further understand the pathogenic mechanism of A. veronii.