title: Genetic variation of dTDP-L-rhamnose pathway genes in Salmonella enterica.
abstract: The genetic variation in the dTDP-L-rhamnose pathway gene set (rmlB, rmlD, rmlA, rmlC) in Salmonella enterica was examined after sequencing the four genes from 11 rml-containing gene clusters encoding seven O antigens, and a 903 bp rmlB segment from another 23 strains representing the seven subspecies. There was considerable sequence variation and strong polarity in the nature and level of variation among rml genes. The 5' end of the rml gene set, including rmlB, rmlD and most of rmlA, is in general subspecies specific. In contrast, the 3' end, including part of rmlA and all of rmlC, is O antigen specific. The G+C content of the 3' end is lower than that of the 5' end. The variation in the 3' end of the gene set is much greater than that of the 5' end. It is apparent that the rml gene set of S. enterica includes genes with two different evolutionary histories. In addition, there has been extensive recombination in the gene set, probably related to O antigen transfer between subspecies. These findings provide evidence for the lateral transfer of O antigen genes between species and among subspecies of S. enterica. The results have also shown that conserved genes at the end of an O antigen gene cluster play a major role in mediating exchange of the central serogroup-specific regions.
authors.affiliation: Department of Microbiology (G08), University of Sydney, NSW 2006, Australia1.
authors.forename: Qun
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Microbiology (G08), University of Sydney, NSW 2006, Australia1.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Reeves
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001482:Base Composition; D001483:Base Sequence; D002238:Carbohydrate Epimerases / Q000235:genetics; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D006836:Hydro-Lyases / Q000235:genetics; D008969:Molecular Sequence Data; D009702:Nucleoside Diphosphate Sugars / Q000235:genetics* / Q000378:metabolism*; D019081:O Antigens / Q000235:genetics; D010802:Phylogeny; D011995:Recombination, Genetic; D019779:Salmonella enterica / Q000235:genetics* / Q000276:immunology; D017422:Sequence Analysis, DNA; D013942:Thymine Nucleotides / Q000235:genetics* / Q000378:metabolism*; D002237:Carbohydrate Dehydrogenases
chemical_list: D001426:Bacterial Proteins; D002238:Carbohydrate Epimerases; D004269:DNA, Bacterial; D006836:Hydro-Lyases; D009702:Nucleoside Diphosphate Sugars; D019081:O Antigens; D013942:Thymine Nucleotides; C073293:thymidine diphosphate rhamnose; C022771:dTDPglucose 4,6-dehydratase; C020092:dTDP-4-ketorhamnose 3,5-epimerase; D002237:Carbohydrate Dehydrogenases