Biopolymer Skeleton Produced by Rhizobium radiobacter: Stoichiometric Alternation of Glycosidic and Amidic Bonds in the Lipopolysaccharide O-Antigen

Immacolata Speciale, Flaviana Di Lorenzo, Valentina Gargiulo, Gitte Erbs, Mari Anne Newman, Antonio Molinaro*, Cristina De Castro

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

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.
Original languageEnglish
JournalAngewandte Chemie - International Edition
Volume59
Issue number16
Pages (from-to)6368-6374
ISSN1433-7851
DOIs
Publication statusPublished - 2020

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