Novel galactofuranan and pyruvylated galactomannan in the cell wall of Clavibacter michiganensis subsp. michiganensis VKM Ac-1403T

Total Synthesis of Conjugation-Ready Hyperbranched Pentasaccharide of Clavibacter phaseoli VKM Ac-2641T by [Au]/[Ag] Catalysis

Infections by Clavibacter spp. cause an economic burden to farmers. The components present in the cell wall glycopolymers (CWGs) are important for studying the host-pathogen interactions, colonization, and infection. A pentasaccharide containing a hyperbranched Ribf-, Galf-, and Manp- has recently been identified. Herein, we describe the first total synthesis of the conjugation-ready hyperbranched pentasaccharide of C. phaseoli VKM Ac-2641T using the [Au]/[Ag]-catalyzed glycosidation chemistry of ethynylcyclohexyl carbonate glycosyl donors. The pentasaccharide was synthesized in a highly convergent fashion from readily accessible monosaccharide building blocks.

A highly branched novel galactofuranan in the cell wall of Clavibacter tesselarius VKM Ac-1406T

The structures of two cell wall glycopolymers were studied in the plant pathogenic bacterium Clavibacter tesselarius VKM Ac-1406^T (family Microbacteriaceae, order Micrococcales, class Actinomycetes). The predominant polymer was a novel (1 → 6)-linked β-d-galactofuranan with a highly branched repeating unit, α-L-Rhap-(1 → 3)-α-D-Galp-(1 → 2)-[α-L-Rhap-(1 → 3)]-α-D-Fucp-(1 →, at O-2 on every second galactofuranose residue. The second polymer present in small amounts was acidic with the repeating unit, →3)-α-D-Galp-(1 → 3)-α-D-[4,6-S-Pyr]-Manp-(1 → 3)-α-D-Manp-[2OAc]_0.2-(1→, and was reported in all Clavibacter species investigated to date. The presented results expand our knowledges of structural diversity of phosphate-free cell wall glycopolymers and provide evidence in support of their taxonomic specificity for bacterial species and genera.

A novel cell wall galactofuranan in Clavibacter phaseoli VKM Ac-2641T

A glycopolymer of novel structure was found in the cell wall of plant pathogen Clavibacter phaseoli VKM Ac-2641^T (family Microbacteriaceae, class Actinomycetes). The glycopolymer was (1 → 6)-linked β-d-galactofuranan with side branched trisaccharide, α-D-Manp-(1 → 2)-[α-D-Manp-(1 → 3)]-α-D-Ribf-(1→ at O-2 on every second galactofuranose residue. The galactofuranan structure was established by chemical and NMR spectroscopic methods using one- and two-dimensional techniques ¹H,¹H COSY, TOCSY, ROESY and ¹H,¹³C HSQC, HMBC. The results of this study provide new data on diversity of bacterial glycopolymers, may prove useful for bacterial taxonomy and contribute to the understanding of the host plant-microbiota interaction mechanisms.

Cell wall galactofuranan and pyruvate-containing galactomannan in the cell walls of Clavibacter strains

The cell wall glycopolymer structures of plant-associated strains Clavibacter sp. VKM Ac-1371, Clavibacter sp. VKM Ac-1372 and Clavibacter sp. VKM Ac-1374, members of three putative new species (family Microbacteriaceae, class Actinobacteria) were studied. Each strain was found to contain two glycopolymers, neutral and acidic ones. The main chain of neutral polymer, identical in all three strains, is (1 → 6)-linked β-d-galactofuranan with every second galactofuranose residue substituted at position 2 by side disaccharide, α-d-Manp-(1 → 2)-α-d-Ribf-(1 → . The second, acidic polymer, is pyruvate-containing galactomannan with the repeating unit, →3)-α-d-Galp-(1 → 3)-α-d-[4,6-S-Pyr]-Manp-(1 → 3)-α-d-Manp-(1 → . Reducing mannopyranose residues of the acidic polysaccharides repeating unit from strains VKM Ac-1372 and VKM Ac-1374 bear O-acetyl residues additionally. The cell wall glycopolymer structures were established by chemical and NMR spectroscopic methods with using one- and two-dimensional techniques ¹H,¹H COSY, TOCSY, ROESY and ¹H,¹³C HSQC, HMBC. The results obtained provide new data on diversity of the bacterial cell wall glycopolymers and may prove valuable for microbial taxonomy and insight into the molecular mechanisms of interactions between bacteria and plants and also of bacterial adaptation to survival in desert systems.