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 of lipopolysaccharides (LPSs). LPSs play 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 by using a combination of GC‐MS, MALDI and NMR techniques. The results revealed a novel repeat of the O‐antigen structure of the LPS, [→4)‐β‐d‐GlcpNAcA‐(1→4)‐β‐d‐GlcpNAc3NAlaA‐(1→3)‐α‐d‐FucpNAc4NR‐(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 might differentially influence recognition by immune cells.