Structure of the O-antigen and the lipid A from the lipopolysaccharide of Fusobacterium nucleatum ATCC 51191.

Fusobacterium nucleatum is a common member of the oral microbiota. However, this symbiont has been found to play an active role in disease development. As a Gram-negative bacterium, F. nucleatum has a protective outer membrane layer whose external leaflet is mainly composed by lipopolysaccharides (LPSs). LPS plays a crucial role in the interaction between bacteria and the host immune system. Here, we characterised the structure of the O-antigen and lipid A from F. nucleatum ssp. animalis ATCC 51191 using a combination of Gas Chromatography - Mass Spectrometry (GC-MS), Matrix-Assisted Laser Desorption/Ionization (MALDI) and Nuclear Magnetic Resonance (NMR) techniques. The results revealed a novel repeat of the O-antigen structure of the LPS, [→4)-β-D-Glc p NAcA-(1→4)-β-D-Glc p NAc3NAlaA-(1→3)-α-D-Fuc p NAc4NR-(1→], (R= Acetylated 60 %), and a bis -phosphorylated hexa-acylated lipid A moiety. Taken together these data showed that F. nucleatum ATCC 51191 has a distinct LPS which may differentially influence recognition by immune cells.