Unveiling the structure of Delftia acidovorans Lipopolysaccharide: insights into O-antigen and lipid A

Delftia acidovorans is a Gram-negative bacterium traditionally considered as an environmental organism, although it has recently been identified as an opportunistic pathogen in immunocompromised patients. Furthermore, this bacterium was also recognized as part of the crypt-specific core microbiota in healthy mice. Despite its detection in various contexts, the chemical structure of its lipopolysaccharide (LPS) remains uncharacterized. Here, the structure of O-antigen and lipid A from Delftia acidovorans were characterized by combining chemical approaches with spectroscopic and spectrometric studies. In detail, the O-antigen is found to consist of a novel glycan sequence composed of 3)-α-l-rhamnose-(1→4)-α-d-glucose-(1→ disaccharide in the linear backbone, where glucose is in turn branched at the O-2 position with a β-d-N-acetyl-glucosamine, that is non-stoichiometrically acetylated at position O-6. Whereas lipid A is predominantly represented by a hexa-acylated species with a symmetric distribution of acyl chains.