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Biopolymer Skeleton Produced by Rhizobium radiobacter : Stoichiometric Alternation of Glycosidic and Amidic Bonds in the Lipopolysaccharide O‐Antigen
Author(s) -
Speciale Immacolata,
Di Lorenzo Flaviana,
Gargiulo Valentina,
Erbs Gitte,
Newman MariAnne,
Molinaro Antonio,
De Castro Cristina
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201914053
Subject(s) - chemistry , glycosidic bond , rhizobium , lipopolysaccharide , antigen , rhamnose , microbiology and biotechnology , biochemistry , biology , polysaccharide , gene , genetics , enzyme , endocrinology
The lipopolysaccharide (LPS) O‐antigen structure of the plant pathogen Rhizobium radiobacter strain TT9 and its possible role in a plant‐microbe interaction was investigated. The analyses disclosed the presence of two O‐antigens, named Poly1 and Poly2. The repetitive unit of Poly2 constitutes a 4‐α‐ l ‐rhamnose linked to a 3‐α‐ d ‐fucose residue. Surprisingly, Poly1 turned out to be a novel type of biopolymer in which the repeating unit is formed by a monosaccharide and an amino‐acid derivative, so that the polymer has alternating glycosidic and amidic bonds joining the two units: 4‐amino‐4‐deoxy‐3‐O‐methyl‐ d ‐fucose and (2′R,3′R,4′S)‐ N ‐methyl‐3′,4′‐dihydroxy‐3′‐methyl‐5′‐oxoproline). Differently from the O‐antigens of LPSs from other pathogenic Gram‐negative bacteria, these two O‐antigens do not activate the oxidative burst, an early innate immune response in the model plant Arabidopsis thaliana, explaining at least in part the ability of this R. radiobacter strain to avoid host defenses during a plant infection process.