Abstract
Aeromonas veronii is one of the main pathogens causing freshwater fish sepsis and ulcer syndrome. This bacterium has caused serious economic losses in the aquaculture industry worldwide, and it has become an important zoonotic and aquatic agent. However, little is known about the molecular mechanism of pathogenesis of A. veronii. In this study, we first constructed an unmarked mutant strain (ΔpreA) by generating an in-frame deletion of the preA gene, which encodes a periplasmic binding protein, to investigate its role in A. veronii TH0426. Our results showed that the motility and biofilm formation ability of ΔpreA were similar to those of the wild-type strain. However, the adhesion and invasion ability in epithelioma papulosum cyprini (EPC) cells were significantly enhanced (2.0-fold). Furthermore, the median lethal dose (LD50) of ΔpreA was 7.6-fold higher than that of the wild-type strain, which illustrates that the virulence of the mutant was significantly enhanced. This finding is also supported by the cytotoxicity test results, which showed that the toxicity of ΔpreA to EPC cells was enhanced 1.3-fold relative to the wild type. Conversely, tolerance test results showed that oxidative stress resistance of ΔpreA decreased 5.9-fold compared to with the wild-type strain. The results suggest that preA may negatively regulate the virulence of A. veronii TH0426 through the regulation of resistance to oxidative stress. These insights will help to further elucidate the function of preA and understand the pathogenesis of A. veronii.
Highlights
Aeromonas veronii is a Gram-negative facultative anaerobe that is widely distributed in nature, especially in freshwater environments, with strong environmental adaptability [1]
A few decades have passed between the initial discovery of A. veronii and the explosive epidemic in many parts of the world; the research on this bacterium has been limited to the isolation and identification of certain diseased organisms and some related phenotypes, while little is known about its pathogenesis and virulence
The mutant strain ∆preA and complemented strain C-preA were generated by homologous recombination to examine the role of the preA gene in A. veronii
Summary
Aeromonas veronii is a Gram-negative facultative anaerobe that is widely distributed in nature, especially in freshwater environments, with strong environmental adaptability [1]. A growing number of cases of large-scale A. veronii outbreaks have resulted in the infection of freshwater fish, livestock, birds, and red meat animals (such as camels). These events can cause severe losses to the breeding industry and threaten food hygiene and safety [2,3,4]. A few decades have passed between the initial discovery of A. veronii and the explosive epidemic in many parts of the world; the research on this bacterium has been limited to the isolation and identification of certain diseased organisms and some related phenotypes, while little is known about its pathogenesis and virulence. An in-depth study of the effects of virulence factors is crucial for elucidating the pathogenesis of A. veronii
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