Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia
Bacteria Shigella, the cause of shigellosis, evolved from the intestinal bacteria Escherichia coli. Based on structurally diverse O-specific polysaccharide chains of the lipopolysaccharides (LPSs; O-antigens), three from four Shigella species are subdivided into multiple serotypes. The central oligosaccharide of the LPS called core is usually conserved within genus but five core types called R1-R4 and K-12 have been recognized in E. coli. Structural data on the Shigella core are limited to S. sonnei, S. flexneri and one S. dysenteriae strain, which all share E. coli core types. In this work, we elucidated the core structure in 14 reference strains of S. dysenteriae and S. boydii. Core oligosaccharides were obtained by mild acid hydrolysis of the LPSs and studied using sugar analysis, high-resolution mass spectrometry and two-dimensional NMR spectroscopy. The R1, R3 and R4 E. coli core types were identified in 8, 3 and 2 Shigella strains, respectively. A novel core variant found in S. boydii type 16 differs from the R3 core in the lack of GlcNAc and the presence of a D-glycero-D-manno-heptose disaccharide extension. In addition, the structure of an oligosaccharide consisting of the core and one O-antigen repeat was determined in S. dysenteriae type 8. A clear correlation of the core type was observed with genetic grouping of Shigella strains but not with their traditional division to four species. This finding supports a notion on the existing Shigella species as invalid taxa and a suggestion of multiple independent origins of Shigella from E. coli clones.
13C NMR, 1H NMR, methylation, GLC-MS, NMR-2D, sugar analysis, 31P NMR, GLC, ESI-ICR-MS
13C NMR data:
Linkage Residue C1 C2 C3 C4 C5 C6 C7
5,3,3,3,2,2 aDGlcp 97.1 72.6 74.1 70.7 73.2 61.6
5,3,3,3,2,6,6 aXDDmanHepp 98.7 71.1 72.0 68.5 74.0 71.4 ?
5,3,3,3,2,6 aXDDmanHepp 100.4 70.9 71.9 68.1 72.0 76.7 ?
5,3,3,3,2 aDGlcp 93.7 76.0 72.6 70.7 71.1 66.6
5,3,3,3 aDGalp 96.5 73.4 68.9 70.4 71.6 62.2
5,3,3 aDGlcp 101.6 71.6 77.9 71.5 73.5 61.6
5,3,7,7 aDGlcpN 97.1 55.2 71.9 70.7 73.5 ?
5,3,7 aXLDmanHepp 101.6 71.5 72.0 67.2 73.1 69.1 72.0
5,3 aXLDmanHepp 103.6 70.7 79.6 66.6 73.7 69.2 71.0
5,4 P
5 aXLDmanHepp 101.1 72.1 78.7 71.3 73.0 69.8 ?
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1H NMR data:
Linkage Residue H1 H2 H3 H4 H5 H6 H7
5,3,3,3,2,2 aDGlcp 5.21 3.58 3.81 3.45 3.94 3.77-3.87
5,3,3,3,2,6,6 aXDDmanHepp 5.04 3.92 3.85 3.81 3.96 4.01 ?
5,3,3,3,2,6 aXDDmanHepp 4.88 3.98 3.87 3.74 3.91 4.15 ?
5,3,3,3,2 aDGlcp 5.49 3.78 3.92 3.51 4.04 3.76-3.86
5,3,3,3 aDGalp 5.78 4.02 4.11 4.08 4.31 3.77-3.81
5,3,3 aDGlcp 5.30 3.69 4.09 3.77 3.87 3.90
5,3,7,7 aDGlcpN 5.21 3.38 3.92 3.51 3.76 ?
5,3,7 aXLDmanHepp 4.97 3.97 3.87 3.87 3.58 4.26 3.73-3.77
5,3 aXLDmanHepp 5.12 4.38 4.04 4.04 3.69 4.16 3.59-3.81
5,4 P
5 aXLDmanHepp 5.18 4.06 4.11 4.48 4.18 4.10 ?
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1H/13C HSQC data:
Linkage Residue C1/H1 C2/H2 C3/H3 C4/H4 C5/H5 C6/H6 C7/H7
5,3,3,3,2,2 aDGlcp 97.1/5.21 72.6/3.58 74.1/3.81 70.7/3.45 73.2/3.94 61.6/3.77-3.87
5,3,3,3,2,6,6 aXDDmanHepp 98.7/5.04 71.1/3.92 72.0/3.85 68.5/3.81 74.0/3.96 71.4/4.01 ?/?
5,3,3,3,2,6 aXDDmanHepp 100.4/4.88 70.9/3.98 71.9/3.87 68.1/3.74 72.0/3.91 76.7/4.15 ?/?
5,3,3,3,2 aDGlcp 93.7/5.49 76.0/3.78 72.6/3.92 70.7/3.51 71.1/4.04 66.6/3.76-3.86
5,3,3,3 aDGalp 96.5/5.78 73.4/4.02 68.9/4.11 70.4/4.08 71.6/4.31 62.2/3.77-3.81
5,3,3 aDGlcp 101.6/5.30 71.6/3.69 77.9/4.09 71.5/3.77 73.5/3.87 61.6/3.90
5,3,7,7 aDGlcpN 97.1/5.21 55.2/3.38 71.9/3.92 70.7/3.51 73.5/3.76 ?/?
5,3,7 aXLDmanHepp 101.6/4.97 71.5/3.97 72.0/3.87 67.2/3.87 73.1/3.58 69.1/4.26 72.0/3.73-3.77
5,3 aXLDmanHepp 103.6/5.12 70.7/4.38 79.6/4.04 66.6/4.04 73.7/3.69 69.2/4.16 71.0/3.59-3.81
5,4 P
5 aXLDmanHepp 101.1/5.18 72.1/4.06 78.7/4.11 71.3/4.48 73.0/4.18 69.8/4.10 ?/?
?XKdo?
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