Structural diversity in Salmonella O antigens and its genetic basis

FEMS Microbiol Rev. 2014 Jan;38(1):56-89. doi: 10.1111/1574-6976.12034. Epub 2013 Aug 2.


This review covers the structures and genetics of the 46 O antigens of Salmonella, a major pathogen of humans and domestic animals. The variation in structures underpins the serological specificity of the 46 recognized serogroups. The O antigen is important for the full function and virulence of many bacteria, and the considerable diversity of O antigens can confer selective advantage. Salmonella O antigens can be divided into two major groups: those which have N-acetylglucosamine (GlcNAc) or N-acetylgalactosamine (GalNAc) and those which have galactose (Gal) as the first sugar in the O unit. In recent years, we have determined 21 chemical structures and sequenced 28 gene clusters for GlcNAc-/GalNAc-initiated O antigens, thus completing the structure and DNA sequence data for the 46 Salmonella O antigens. The structures and gene clusters of the GlcNAc-/GalNAc-initiated O antigens were found to be highly diverse, and 24 of them were found to be identical or closely related to Escherichia coli O antigens. Sequence comparisons indicate that all or most of the shared gene clusters were probably present in the common ancestor, although alternative explanations are also possible. In contrast, the better-known eight Gal-initiated O antigens are closely related both in structures and gene cluster sequences.

Keywords: evolution; glycosyltransferase; pathogen; polymorphism; polysaccharide; serotyping.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Escherichia coli / genetics
  • Monosaccharides / biosynthesis
  • Multigene Family / genetics
  • O Antigens / chemistry*
  • O Antigens / genetics*
  • Protein Structure, Secondary
  • Salmonella / genetics*
  • Salmonella / pathogenicity
  • Virulence / genetics


  • Monosaccharides
  • O Antigens