Structural investigation of an exopolysaccharide substituted with a lactyl ether group produced by Raoultella terrigena Ez-555-6 isolated in the Chernobyl exclusion zone.
Raoultella terrigena strain Ez-555-6, isolated from a root nodule of Medicago sativa harvested in the Chernobyl exclusion zone, produces a non-referenced high-molecular-mass exopolysaccharide (EPS). The structure of this EPS was determined using a combination approach including monosaccharide composition (GLC-FID, HPAEC-PAD), determination of glycosylation sites (GLC-EIMS) and 1D/2D NMR ((1)H, (13)C) and ESIMS (HR, MS/MS) studies of oligosaccharides obtained from mild acid hydrolysis. The EPS was found to be a charged pentasaccharide with a repeating unit composed of D-galactose, D-glucose, D-mannose and D-glucuronic acid (1:2:1:1). Lactic acid and O-acetyl substituents were localized on galactose and glucose residues, respectively, as presented in the following structure:
Pillon
M
M
Laboratoire des Polysaccharides Microbiens et Végétaux, Université de Picardie Jules Verne, IUT d'Amiens, Avenue des Facultés, Amiens, France.
Pau-Roblot
C
C
Lequart
V
V
Pilard
S
S
Courtois
B
B
Courtois
J
J
Pawlicki-Jullian
N
N
D002240:Carbohydrate Sequence; D047852:Chernobyl Nuclear Accident; D004755:Enterobacteriaceae / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry*; D006027:Glycosides / Q000737:chemistry; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000302:isolation & purification*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
D004987:Ethers; D006027:Glycosides; D009005:Monosaccharides; D011135:Polysaccharides, Bacterial