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Genetic and structural relationships of Salmonella O55 and Escherichia coli O103 O-antigens and identification of a 3-hydroxybutanoyltransferase gene involved in the synthesis of a Fuc3N derivative
Stockholm University, Faculty of Science, Department of Organic Chemistry.
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2010 (English)In: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 20, no 6, 679-688 p.Article in journal (Refereed) Published
Abstract [en]

O-antigen (O-polysaccharide), a part of the outer membrane of Gram-negative bacteria, is one of the most variable cell constituents and is related to bacterial virulence. O-antigen diversity is almost entirely due to genetic variations in O-antigen gene clusters. In this study, the O-polysaccharide structures of Salmonella O55 and Escherichia coli O103 were elucidated by chemical analysis and nuclear magnetic resonance spectroscopy. It was found that the O-polysaccharides have similar pentasaccharide O-units, which differ only in one sugar (glucose versus N-acetylglucosamine) and in the N-acyl group (acetyl versus 3-hydroxybutanoyl) on 3-amino-3,6-dideoxy-d-galactose (d-Fuc3N). The Salmonella O55 antigen gene cluster was sequenced and compared with the E. coli O103 antigen gene cluster reported previously. The two gene clusters were found to share high-level similarity (DNA identity ranges from 53% to 76%), except for two putative acyl transferase genes (fdtC in Salmonella O55 and fdhC in E. coli O103) which show no similarity. Replacement of the fdtC gene in Salmonella O55 with the fdhC gene from E. coli O103 resulted in production of a modified O-antigen, which contains a 3-hydroxybutanoyl derivative of Fuc3N in place of 3-acetamido-3,6-dideoxygalactose. This finding strongly suggests that fdhC is a 3-hydroxybutanoyltransferase gene. The sequence similarity level suggested that the O-antigen gene clusters of Salmonella O55 and E. coli O103 originate from a common ancestor, and this evolutionary relationship is discussed.

Place, publisher, year, edition, pages
Oxford University Press , 2010. Vol. 20, no 6, 679-688 p.
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-39137DOI: 10.1093/glycob/cwq015ISI: 000277448400004OAI: oai:DiVA.org:su-39137DiVA: diva2:318683
Available from: 2010-05-10 Created: 2010-05-10 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Structural and Conformational Studies of Oligo- and Polysaccharides
Open this publication in new window or tab >>Structural and Conformational Studies of Oligo- and Polysaccharides
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The focus of this thesis is to examine the structural properties of polysaccharides produced by bacteria, as well as the dynamic and conformational behavior of a synthetically derived oligosaccharide.

The primary structures of the O-polysaccharide repeating units of four different Escherichia coli (E. coli) strains, namely O175, O177, O103 and TD2158, as well as the first report of a capsular polysaccharide produced by lactic acid bacteria Leuconostoc mesenteroides ssp. cremoris PIA2 are reported in paper I–V. Structural analyses have been performed using a combination of nuclear magnetic resonance spectroscopy and chemical component analysis.

The elucidated structures in paper I–III, as well as paper V, are composed of linear repeating units of varying composition and length. In paper IV, the structure of the O-polysaccharide repeating unit of E. coli TD2158 is determined to be a branched hexasaccharide structure with a heterogeneous substitution pattern, with either a β-GlcpNAc or β-Glcp residue branching to the backbone chain. Incubation with bacteriophage HK620 tailspike protein shows that the polysaccharide is selectively cleaved at the α-GlcpNAc-(1→2)-α-Rhap-linkage of the backbone chain, yielding a 9:1 ratio of β-GlcpNAc/β-Glcp containing hexasaccharides after digestion.

In paper VI the conformational properties of a trisaccharide, which constitutes an internal epitope of the LeaLex hexasaccharide over-expressed on the surface of squamous lung cancer cells, have been analyzed using NMR spectroscopy and molecular dynamics simulations. The β-(1→3)-linkage of the trisaccharide was shown to be highly flexible.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2012. 54 p.
Keyword
NMR spectroscopy, structural analysis, conformational analysis, carbohydrates, polysaccharides
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-75050 (URN)978-91-7447-457-2 (ISBN)
Public defence
2012-05-04, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
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Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 6: Submitted.

Available from: 2013-04-09 Created: 2012-04-03 Last updated: 2013-11-18Bibliographically approved

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