title: Extensive variation in the O-antigen gene cluster within one Salmonella enterica serogroup reveals an unexpected complex history.
abstract: The 46 serogroups of Salmonella enterica have different O-antigens, and each is thought to have a specific form of the O-antigen cluster. Comparison of the 145 serovars of serogroup B revealed much more intraserogroup genetic diversity than expected. The O27 factor, due to an alpha 1-6 linkage between O units in place of the more common alpha 1-2 linkage and previously thought to be due to a converting bacteriophage, is now shown to be due to a wzy(alpha(1-6)) gene located within the major gene cluster. Surprisingly a remnant of this gene in all O27(-) serovars shows that the ancestor was O27(+). There are six distinct gene cluster forms, five apparently derived by a series of deletions and one by an insertion from an ancestral O27(+) form present in 57 serovars. The history of the gene cluster and movement between subspecies I and II can be traced. Two of the derivative forms still have a functional wzy(alpha(1-6)) gene, while in three it has been inactivated by deletion or insertion. Two of the forms lacking a functional wzy(alpha(1-6)) gene have the wzy(alpha(1-2)) gene first described for strain LT2 as rfc, whereas for the third the wzy gene has not been located.
authors.affiliation: Department of Microbiology, The University of Sydney, Sydney, New South Wales 2006, Australia.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Kanella
authors.initials: K
authors.lastname: Andrianopoulos
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.forename: Michel Y
authors.initials: MY
authors.lastname: Popoff
authors.forename: Peter R
authors.initials: PR
authors.lastname: Reeves
mesh_terms: D003001:Cloning, Molecular; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D014644:Genetic Variation; D008969:Molecular Sequence Data; D005810:Multigene Family; D019081:O Antigens / Q000235:genetics*; D019779:Salmonella enterica / Q000235:genetics* / Q000276:immunology
chemical_list: D019081:O Antigens