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Unfolding and refolding properties of S pili on extraintestinal pathogenic Escherichia coli
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). (Uhlin)
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). (Uhlin)
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2010 (English)In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 39, no 8, 1105-1115 p.Article in journal (Refereed) Published
Abstract [en]

S pili are members of the chaperone-usher-pathway-assembled pili family that are predominantly associated with neonatal meningitis (S(II)) and believed to play a role in ascending urinary tract infections (S(I)). We used force-measuring optical tweezers to characterize the intrinsic biomechanical properties and kinetics of S(II) and S(I) pili. Under steady-state conditions, a sequential unfolding of the layers in the helix-like rod occurred at somewhat different forces, 26 pN for S(II) pili and 21 pN for S(I) pili, and there was an apparent difference in the kinetics, 1.3 and 8.8 Hz. Tests with bacteria defective in a newly recognized sfa gene (sfaX (II)) indicated that absence of the sfaX (II) gene weakens the interactions of the fimbrium slightly and decreases the kinetics. Data of S(I) are compared with those of previously assessed pili primary associated with urinary tract infections, the P and type 1 pili. S pili have weaker layer-to-layer bonds than both P and type 1 pili, 21, 28 and 30 pN, respectively. In addition, the S pili kinetics are ~10 times faster than the kinetics of P pili and ~550 times faster than the kinetics of type 1 pili. Our results also show that the biomechanical properties of pili expressed ectopically from a plasmid in a laboratory strain (HB101) and pili expressed from the chromosome of a clinical isolate (IHE3034) are identical. Moreover, we demonstrate that it is possible to distinguish, by analyzing force-extension data, the different types of pili expressed by an individual cell of a clinical bacterial isolate.

Place, publisher, year, edition, pages
2010. Vol. 39, no 8, 1105-1115 p.
Keyword [en]
Fimbriae, uropathogenic escherichia coli, bond breaking, unfolding, optical tweezers
National Category
Cell and Molecular Biology
URN: urn:nbn:se:umu:diva-32913DOI: 10.1007/s00249-009-0552-8ISI: 000279194500001PubMedID: 19885656OAI: diva2:306675
Available from: 2010-03-30 Created: 2010-03-30 Last updated: 2012-08-27Bibliographically approved
In thesis
1. Pathogenecity-associated genes modulate Escherichia coli adhesion and motility
Open this publication in new window or tab >>Pathogenecity-associated genes modulate Escherichia coli adhesion and motility
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Escherichia coli strains typical of UPEC (uropathogenic E. coli) and NBM (newborn meningitis) isolates carry chromosomally located PAIs (pathogenicity islands) that are absent in non-pathogenic E. coli strains. The PAIs include genes for virulence factors such as toxins and genes coding for specific adhesins and pili/fimbriae formation. Commonly, the gene clusters for such fimbriae in E. coli consist of a set of genes for biogenesis of the actual fimbriae organelles: a chaperone, an usher, the fimbrial subunits, and an adhesin, as well as some regulatory genes. Genetic studies of the fimbrial gene clusters in PAIs containing the pap genes, the prs genes, or the sfa genes led to the discovery of nearby open reading frames coding for putative cytoplasmic 17 kDa proteins — the X genes. Molecular genetic studies of the sfaXII locus in the clinical NMEC isolate IHE3034 have been performed. The results suggested that expression of the sfaXII gene had regulatory functions affecting both type 1 fimbriae expression and the flagella-mediated motility.

Type 1 fimbriae expression was found to be affected at the level of fim operon transcription and a major reason was SfaXII-mediated modulation of expression from the fimB and fimE recombinase genes. Quantification of SfaII-fimbriated bacteria in a comparison between wild type and SfaXII mutant strains gave no indication that the sfaXII gene product also would be affecting expression and/or biogenesis of SfaII fimbriae.

Biomechanical properties of the SfaII fimbriae produced by wild type and the sfaXII mutant IHE3034 were studied using force measuring optical tweezers (FMOT) and compared to other PAI-encoded fimbriae as well as to the type 1 fimbriae encoded on the core chromosome. The FMOT methodology assesses unfolding and refolding properties and we found that S fimbriae had weaker layer-to-layer interactions than both P and type 1 fimbriae, however the unfolding kinetics was slightly faster.

The expression profile and regulation of the sfaXII gene were determined by use of reporter gene fusions and it was found that expression was affected by environmental cues such as pH, osmolarity and temperature. It was also discovered that the nucleoid structuring protein H-NS and the sigma factor RpoS had strong direct or indirect repressive effects on sfaXII gene expression.

Further genomic analysis of the PAI fimbrial operons revealed that in some cases an additional ORF was found between the X genes and the fimbrial adhesion genes. Examination of the sfaII operon in IHE3034 indicated that this new gene, denoted sfaYII, coded for a protein that had the EAL domain motif and thereby could be considered a putative phosphodiesterase involved in controlling the level of cyclic-di-GMP in the bacterial cells.

Place, publisher, year, edition, pages
Umeå: Molekylärbiologi, 2009. 49 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1266
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
urn:nbn:se:umu:diva-22302 (URN)987-91-7264-789-3 (ISBN)
Molekylärbiologi (Medicinska fakulteten), 901 87, Umeå
Public defence
2009-05-28, Major Groove, Byggnad 6L, Institutionen för Molekylärbiologi, Umeå Universitet, Umeå, 10:00 (English)
Available from: 2009-05-15 Created: 2009-05-05 Last updated: 2010-04-07Bibliographically approved

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Castelain, MickaëlSjöström, Annika EFällman, ErikUhlin, Bernt EricAndersson, Magnus
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Department of PhysicsDepartment of Molecular Biology (Faculty of Medicine)
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