Structural Studies of the O‐Chain Polysaccharide from Plesiomonas shigelloides Strain 302–73 (Serotype O1)

Abstract

AbstractPlesiomonas shigelloides is a Gram‐negative bacterium belonging to the Enterobacteriaceae family. It has been found in an aquatic environment in the tropical and subtropical regions and is responsible for many gastrointestinal infections in humans, which take place from drinking untreated water or eating uncooked shellfish. Plesiomonas shigelloides has also been reported to provoke extraintestinal infections such as meningitis and bacteremia in immunocompromised adults and neonates. Despite the emerging importance of this pathogenic microorganism, only three different O‐antigens have been characterised so far. The structure of the O‐chain of the lipopolysaccharide (LPS) from Plesiomonas shigelloides strain 302–73 (serotype O1) was determined by chemical analysis, 1D and 2D NMR spectroscopy and MALDI‐TOF mass spectrometry. The polysaccharide was constituted by a linear pentasaccharidic repeating unit as follows: →3)‐α‐L‐PneNAc4OAc(1→4)‐α‐L‐FucNAc(1→4)‐α‐L‐FucNAc(1→4)‐α‐L‐FucNAc(1→3)‐β‐D‐QuiNAc4NHb(1→ (PneNAc = 2‐acetamido‐2,6‐dideoxy‐talose, Hb = (S)‐3‐hydroxybutanoyl) PneNAc O‐acetylation was not stoichiometric and was found to be about 75 %. The position of the O‐acetyl group and the amount of acetylation were deduced by NMR spectroscopic analysis. All the monosaccharides included in the repeating unit were deoxyamino sugars, which most probably, together with the presence of O‐acetyl groups, were responsible for the recovery of the LPS in the phenol layer of the phenol/water extract of dried bacteria cells.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)