Characterization of the membrane vesicle fraction from Acetobacter sp. WSS15.

A bacterium that produces membrane vesicles (MVs), strain WSS15, was isolated from a traditional vinegar in Japan called Kurozu. A phylogenetic analysis of 16S rRNA gene sequences indicated that this bacterium belongs to the genus Acetobacter. MVs and peptidoglycan-associated lipoprotein (Pal) were detected in the MV fraction of strain WSS15. In the presence of the WSS15 MV fraction, murine macrophages produced the pro-inflammatory cytokine interleukin-6 (IL-6) via the recognition by superficial Toll-like receptor 2 (TLR2). WSS15 MVs adhered to the cell surface of macrophages. The macrophages secreted IL-6 through the TLR2 recognition of an acylated N-terminal peptide of Pal. We elucidated the mode of action of WSS15 MVs on immune cells and identified the Pal peptide from strain WSS15 as an agonist of TLR2.