title: Structure of the O antigen of Escherichia coli K-12 and the sequence of its rfb gene cluster.
abstract: Escherichia coli K-12 has long been known not to produce an O antigen. We recently identified two independent mutations in different lineages of K-12 which had led to loss of O antigen synthesis (D. Liu and P. R. Reeves, Microbiology 140:49-57, 1994) and constructed a strain with all rfb (O antigen) genes intact which synthesized a variant of O antigen O16, giving cross-reaction with anti-O17 antibody. We determined the structure of this O antigen to be -->2)-beta-D-Galf-(1-->6)-alpha-D-Glcp- (1-->3)-alpha-L-Rhap-(1-->3)-alpha-D-GlcpNAc-(1-->, with an O-acetyl group on C-2 of the rhamnose and a side chain alpha-D-Glcp on C-6 of GlcNAc. O antigen synthesis is rfe dependent, and D-GlcpNAc is the first sugar of the biological repeat unit. We sequenced the rfb (O antigen) gene cluster and found 11 open reading frames. Four rhamnose pathway genes are identified by similarity to those of other strains, the rhamnose transferase gene is identified by assay of its product, and the identities of other genes are predicted with various degrees of confidence. We interpret earlier observations on interaction between the rfb region of Escherichia coli K-12 and those of E. coli O4 and E. coli Flexneri. All K-12 rfb genes were of low G+C content for E. coli. The rhamnose pathway genes were similar in sequence to those of (Shigella) Dysenteriae 1 and Flexneri, but the other genes showed distant or no similarity. We suggest that the K-12 gene cluster is a member of a family of rfb gene clusters, including those of Dysenteriae 1 and Flexneri, which evolved outside E. coli and was acquired by lateral gene transfer.
authors.affiliation: Department of Microbiology, University of Sydney, New South Wales, Australia.
authors.forename: G
authors.initials: G
authors.lastname: Stevenson
authors.forename: B
authors.initials: B
authors.lastname: Neal
authors.forename: D
authors.initials: D
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Hobbs
authors.forename: N H
authors.initials: NH
authors.lastname: Packer
authors.forename: M
authors.initials: M
authors.lastname: Batley
authors.forename: J W
authors.initials: JW
authors.lastname: Redmond
authors.forename: L
authors.initials: L
authors.lastname: Lindquist
authors.forename: P
authors.initials: P
authors.lastname: Reeves
mesh_terms: D000107:Acetylation; D001483:Base Sequence; D005075:Biological Evolution; D002238:Carbohydrate Epimerases / Q000235:genetics; D002240:Carbohydrate Sequence; D003429:Cross Reactions; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D029968:Escherichia coli Proteins; D005690:Galactose / Q000378:metabolism; D005798:Genes, Bacterial / Q000235:genetics*; D005947:Glucose / Q000378:metabolism; D006602:Hexosyltransferases / Q000235:genetics; D006836:Hydro-Lyases / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D008359:Mannose-6-Phosphate Isomerase; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000235:genetics; D019081:O Antigens; D016366:Open Reading Frames / Q000235:genetics; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D015183:Restriction Mapping; D013942:Thymine Nucleotides / Q000378:metabolism; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics; D001426:Bacterial Proteins; D002237:Carbohydrate Dehydrogenases
chemical_list: D002238:Carbohydrate Epimerases; D029968:Escherichia coli Proteins; D005690:Galactose; D005947:Glucose; D006602:Hexosyltransferases; D006836:Hydro-Lyases; D008359:Mannose-6-Phosphate Isomerase; D008565:Membrane Proteins; D017351:N-Acetylglucosaminyltransferases; D009702:Nucleoside Diphosphate Sugars; D009713:Nucleotidyltransferases; D019081:O Antigens; D011135:Polysaccharides, Bacterial; D013942:Thymine Nucleotides; D017855:Transferases (Other Substituted Phosphate Groups); C073293:thymidine diphosphate rhamnose; C085652:O-antigen polymerase; C023227:UDP-N-acetylglucosamine transferase; C085243:dTDP-D-glucose synthase; C083617:wecA protein, E coli; C022771:dTDPglucose 4,6-dehydratase; C020092:dTDP-4-ketorhamnose 3,5-epimerase; D001426:Bacterial Proteins; D002237:Carbohydrate Dehydrogenases