Role of msbB Gene in Physiology and Pathogenicity of Vibrio parahaemolyticus

The <i>msbB</i> 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 <i>msbB</i> in <i>Vibrio parahaemolyticus</i>, a significant marine pathogen causing gastroenteritis in humans and infections in aquatic animals. We constructed an <i>msbB</i> deletion mutant (Δ<i>msbB</i>) and a complementary strain (CΔ<i>msbB</i>) using homologous recombination. The growth, outer membrane permeability, stress and antibiotic sensitivity, biofilm formation, swarming motility, and virulence of the wild-type (WT), Δ<i>msbB</i>, and CΔ<i>msbB</i> strains were assessed. Additionally, the pathogenicity of Δ<i>msbB</i> was evaluated using <i>L. vannamei</i> shrimp models. The results showed that the <i>msbB</i> gene was successfully deleted and complemented, and its deletion did not impair bacterial growth. However, the Δ<i>msbB</i> strain exhibited an increased outer membrane permeability, reduced resistance to stresses and antibiotics, defective biofilm formation, and a reduced swarming motility. In a <i>Tetrahymena</i> co-culture, the Δ<i>msbB</i> strain showed attenuated virulence. In shrimp infected with the Δ<i>msbB</i> 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 Δ<i>msbB</i> group, indicating a significant reduction in infection capability and pathogenicity. These findings indicate that the <i>msbB</i> gene is critical for the virulence of <i>V. parahaemolyticus</i> and suggest that <i>msbB</i> is a potential target for therapeutic interventions and vaccine development against <i>V. parahaemolyticus</i> infections.