Site-Specific Incorporation of Clickable d-Mannose Derivatives in the Lipopolysaccharide Core of the Pathogen Brucella abortus

Brucellae are pathogenic bacteria responsible for a worldwide zoonosis called brucellosis. In this study, we exploit the d-mannose central metabolism for the selective labeling of lipopolysaccharide (LPS), a key virulence factor in Gram-negative bacteria. Our approach provides chemical tools to allow selective derivatization of bacterial membranes in vivo and a handle for imaging studies. Using Brucella abortus mutants, we demonstrate that the clickable monosaccharides are exclusively incorporated into the lateral branch of the core LPS glycan but not in the O-chain or any other cell wall component. The metabolic route followed by the mannose analogues was also evidenced and showed that phosphomutase ManB, whose XRD 3D-structure was solved, was the metabolic entry of azidosugars, which do not follow a salvage pathway. Site-specific incorporation of mannose in the LPS core opens new perspectives such as the identification of macromolecules binding this important structure for the host-pathogen interaction.