title: Structural diversity in Salmonella O antigens and its genetic basis.
abstract: 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.
authors.affiliation: TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, China; The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Yuriy A
authors.initials: YA
authors.lastname: Knirel
authors.forename: Lu
authors.initials: L
authors.lastname: Feng
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Perepelov
authors.forename: Sof'ya N
authors.initials: SN
authors.lastname: Senchenkova
authors.forename: Peter R
authors.initials: PR
authors.lastname: Reeves
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
mesh_terms: D004926:Escherichia coli / Q000235:genetics; D009005:Monosaccharides / Q000096:biosynthesis; D005810:Multigene Family / Q000235:genetics; D019081:O Antigens / Q000737:chemistry* / Q000235:genetics*; D017433:Protein Structure, Secondary; D012475:Salmonella / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics
chemical_list: D009005:Monosaccharides; D019081:O Antigens
keywords: evolution; glycosyltransferase; pathogen; polymorphism; polysaccharide; serotyping