Background and aim: Lipopolysaccharide derived from a symbiotic bacterium in wheat (Pantoea agglomerans, LPSp) has shown multiple positive effects, such as prophylactic, antiallergic and antitumour effects, without serious side-effects. LPSp has differential biological activities in comparison to other LPS, such as those from Escherichia coli (LPSe). The only difference between LPSp and LPSe is in the O-antigen polysaccharide structure (O-PS). This led us to the hypothesis that the O-PS structure would seem to participate in biological activities. Thus, the characterization of properties of O-PS in LPS is of the utmost importance for understanding cell activation in the maintenance of homeostasis. However, little is known about the correlation between the O-PS structure of LPS and its biological activities. In this study, we extracted LPS derived from a symbiotic bacterium in rice (strain A46, related species of Pantoea), which has a long history of use in foods, and investigated its putative structures and functions.
Materials and methods: LPS derived from strain A46 was prepared using a hot phenol extraction method. The properties of LPS-A46 were analysed by thin-layer chromatography, Tricine SDS-PAGE and Western blotting. The function of LPS-A46 was analyzed by quantative real-time PCR and flow cytometry using THP-1 cells and Peripheral blood mononuclear cell (PBMC) derived macrophages.
Results: In Tricine SDS-PAGE, high molecular mass LPS-A46 had a molecular mass lower than that of LPSp. In Western blotting, LPS-A46 reacted with lipid A antibody but did not react with an O-PS antibody of LPSp. In comparison to other LPS, LPS-A46 induced a differential cytokine gene expression profile in THP-1 cells and PBMC-derived macrophages.
Conclusion: The present study suggests that LPS derived from symbiotic bacterium in rice is a bioactive functional LPS which may have different functional activities compared to other types of LPS.