Abstract
The msbB gene, encoding a lipid A phosphatease, is crucial for lipopolysaccharide (LPS) synthesis in Gram-negative bacteria and plays a critical role in their virulence. This study investigated the role of msbB in Vibrio parahaemolyticus, a significant marine pathogen causing gastroenteritis in humans and infections in aquatic animals. We constructed an msbB deletion mutant (ΔmsbB) and a complementary strain (CΔmsbB) using homologous recombination. The growth, outer membrane permeability, stress and antibiotic sensitivity, biofilm formation, swarming motility, and virulence of the wild-type (WT), ΔmsbB, and CΔmsbB strains were assessed. Additionally, the pathogenicity of ΔmsbB was evaluated using L. vannamei shrimp models. The results showed that the msbB gene was successfully deleted and complemented, and its deletion did not impair bacterial growth. However, the ΔmsbB strain exhibited an increased outer membrane permeability, reduced resistance to stresses and antibiotics, defective biofilm formation, and a reduced swarming motility. In a Tetrahymena co-culture, the ΔmsbB strain showed attenuated virulence. In shrimp infected with the ΔmsbB strain, the cumulative mortality rate was 22%, significantly lower than the 62% observed in the WT strain. Moreover, the expression levels of immune-related genes in the shrimp hepatopancreas were significantly lower in the ΔmsbB group, indicating a significant reduction in infection capability and pathogenicity. These findings indicate that the msbB gene is critical for the virulence of V. parahaemolyticus and suggest that msbB is a potential target for therapeutic interventions and vaccine development against V. parahaemolyticus infections.