Extensive DNA inversions in the B. fragilis genome control variable gene expression

Ana M. Cerdeño-Tárraga, Sheila Patrick, Lisa C. Crossman, Garry Blakely, Val Abratt, Nicola Lennard, Ian Poxton, Brian Duerden, Barbara Harris, Mike A. Quail, Andrew Barron, Louise Clark, Craig Corton, Jonathan Doggett, Matthew T.G. Holden, Natasha Larke, Alexandra Line, Angela Lord, Halina Norbertczak, Doug OrmondClaire Price, Ester Rabbinowitsch, John Woodward, Bart Barrell, Julian Parkhill

Research output: Contribution to journalArticlepeer-review

235 Citations (Scopus)


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 dusters identified (7 with associated invertible promoters) suggests a mechanism of synthesis similar to the O-antigen capsules of Escherichia coli.

Original languageEnglish
Pages (from-to)1463-1465
Number of pages3
Issue number5714
Publication statusPublished - 4 Mar 2005

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