Abstract
Helicobacter pylori (H. pylori) infects more than 50% of the world population and results in gastritis, peptic ulceration and gastric adenocarcinoma. In spite of the identification of numerous virulence factors, the detailed mechanism of pathogenesis and long-term infection of this bacterium remain illusive. Therefore, finding a key gene of virulence and pathogenicity is important for generating a treatment against H. pylori infection. BabA is the first adhesin found in H. pylori and has been demonstrated to bind to Lewis b. Lipopolysaccharide (LPS) is essential for the physical integrity of the outer membrane in Gram-negative bacteria and plays an important role in immunostimulation of the infected hosts. It is composed of lipid A, core oligosaccharide (including inner core and outer core) and O-antigen. Previously, our laboratory had identified HP0859 is involved in the biosynthesis of H. pylori LPS inner core. Surprisingly, the knockout of HP0859 not only shortens the LPS structure but also decreases the molecule weight of several key adhesins. We proposed that the disruption of HP0859 alters the glycosylation status of adhesins, and the glycosylation of key adhesins plays a vital role in H. pylori adhesion. In this study, we constructed the corresponding mutants and tested the adhesion and pathogenesis ability of WT, Δ0859, ΔBabA and Δ0859/ΔBabA. Interestingly, the molecular size of BabA was indeed reduced in Δ0859. The permeability and hydrophobicity of outer membrane were significantly increased in Δ0859 and Δ0859/ΔBabA, and the hydrophobicity in ΔBabA was slightly increased along with the increasing time of standing. We also found that ΔBabA lacked Lewis x in the O-antigen of LPS. In comparison, ΔBabA lost only a part of adhesion ability and CagA translocation, but Δ0859 and Δ0859/ΔBabA markedly abolished these abilities. This observation implied that H. pylori requires tight adhesion to host cells to promote the formation of type IV secretion system (T4SS) to inject the Cag A, and the disruption of bab A expression will not completely inhibit H. pylori adhesion. In contrast, the disruption of HP0859 gene involved in the LPS inner core biosynthesis can alter the glycosylation status in all of the key adhesins (including BabA) and thus significantly reduce H. pylori adhesion.