title: Extensive DNA inversions in the B. fragilis genome control variable gene expression.
abstract: The obligately anaerobic bacterium Bacteroides fragilis, an opportunistic pathogen and inhabitant of the normal human colonic microbiota, exhibits considerable within-strain phase and antigenic variation of surface components. The complete genome sequence has revealed an unusual breadth (in number and in effect) of DNA inversion events that potentially control expression of many different components, including surface and secreted components, regulatory molecules, and restriction-modification proteins. Invertible promoters of two different types (12 group 1 and 11 group 2) were identified. One group has inversion crossover (fix) sites similar to the hix sites of Salmonella typhimurium. There are also four independent intergenic shufflons that potentially alter the expression and function of varied genes. The composition of the 10 different polysaccharide biosynthesis gene clusters identified (7 with associated invertible promoters) suggests a mechanism of synthesis similar to the O-antigen capsules of Escherichia coli.
authors.affiliation: Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Cerdeño-Tárraga
authors.forename: Sheila
authors.initials: S
authors.lastname: Patrick
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Crossman
authors.forename: Garry
authors.initials: G
authors.lastname: Blakely
authors.forename: Val
authors.initials: V
authors.lastname: Abratt
authors.forename: Nicola
authors.initials: N
authors.lastname: Lennard
authors.forename: Ian
authors.initials: I
authors.lastname: Poxton
authors.forename: Brian
authors.initials: B
authors.lastname: Duerden
authors.forename: Barbara
authors.initials: B
authors.lastname: Harris
authors.forename: Mike A
authors.initials: MA
authors.lastname: Quail
authors.forename: Andrew
authors.initials: A
authors.lastname: Barron
authors.forename: Louise
authors.initials: L
authors.lastname: Clark
authors.forename: Craig
authors.initials: C
authors.lastname: Corton
authors.forename: Jonathan
authors.initials: J
authors.lastname: Doggett
authors.forename: Matthew T G
authors.initials: MT
authors.lastname: Holden
authors.forename: Natasha
authors.initials: N
authors.lastname: Larke
authors.forename: Alexandra
authors.initials: A
authors.lastname: Line
authors.forename: Angela
authors.initials: A
authors.lastname: Lord
authors.forename: Halina
authors.initials: H
authors.lastname: Norbertczak
authors.forename: Doug
authors.initials: D
authors.lastname: Ormond
authors.forename: Claire
authors.initials: C
authors.lastname: Price
authors.forename: Ester
authors.initials: E
authors.lastname: Rabbinowitsch
authors.forename: John
authors.initials: J
authors.lastname: Woodward
authors.forename: Bart
authors.initials: B
authors.lastname: Barrell
authors.forename: Julian
authors.initials: J
authors.lastname: Parkhill
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001441:Bacteroides fragilis / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D001483:Base Sequence; D007446:Chromosome Inversion; D004269:DNA, Bacterial / Q000235:genetics*; D021901:DNA, Intergenic; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D045522:Recombinases / Q000235:genetics; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; D021901:DNA, Intergenic; D011135:Polysaccharides, Bacterial; D045522:Recombinases