title: FimE-catalyzed off-to-on inversion of the type 1 fimbrial phase switch and insertion sequence recruitment in an Escherichia coli K-12 fimB strain.
abstract: We have investigated the capacity of a well-defined Escherichia coli fimB strain, AAEC350 (a derivative of MG1655), to express type 1 fimbriae under various growth conditions. The expression of type 1 fimbriae is phase-variable due to the inversion of a 314-bp DNA segment. Two tyrosine recombinases, FimB and FimE, mediate the inversion of the phase switch. FimB can carry out recombination in both directions, whereas the current evidence suggests that FimE-catalyzed switching is on-to-off only. We show here that AAEC350 is in fact capable of off-to-on phase switching and type 1 fimbrial expression under aerobic static growth conditions. The phase switching is mediated by FimE, and allows emerging fimbriate AAEC350 to outgrow their non-fimbriate counterparts by pellicle formation. Following inversion of the phase switch, this element can remain phase-locked in the on orientation due to integration of insertion sequence elements, viz. IS1 or IS5, at various positions in either the fimE gene or the phase switch.
authors.affiliation: Department of Microbiology, Bldg 301, Technical University of Denmark, DK-2800, Lyngby, Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Stentebjerg-Olesen
authors.forename: T
authors.initials: T
authors.lastname: Chakraborty
authors.forename: P
authors.initials: P
authors.lastname: Klemm
mesh_terms: D000371:Agglutination; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D019426:Integrases; D016133:Polymerase Chain Reaction / Q000379:methods; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C081956:fimB protein, E coli; C081955:fimE protein, E coli; D019426:Integrases