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Analysis of the sfaXII locus in the Escherichia coli meningitis isolate IHE3034 reveals two novel regulatory genes within the promoter-distal region of the main S fimbrial operon
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
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2009 (English)In: Microbial Pathogenesis, ISSN 0882-4010, E-ISSN 1096-1208, Vol. 46, no 3, 150-158 p.Article in journal (Refereed) Published
Abstract [en]

We describe the expression and regulation of the gene sfaXII located near the SfaII fimbrial determinant in the newborn meningitis Escherichia coli (NMEC) isolate IHE3034. sfaXII belongs to a gene family, the 17kDa genes, typically located downstream (300 – 3000 bp) of different fimbrial operons found in E. coli isolates of uropathogenic and newborn meningitis origin. Using transcriptional sfaXII reporter gene fusions we found that different environmental conditions commonly affecting expression of fimbrial genes also affected sfaXII expression. Analysis of the sfaXII transcripts showed that the gene is part of the main fimbrial operon as it is transcribed together with the rest of the fimbrial genes. In addition, the sfaXII gene can be expressed from a more proximal promoter and is found to be subject to strong down-regulation by the nucleoid protein H-NS. Studies with an sfaXII mutant derivative of IHE3034 did not reveal effects on SfaII fimbrial biogenesis as monitored by e.g. immunofluorescence microscopy. Nevertheless, a mutation in sfaXII resulted in altered expression of other surface components. Moreover, we define a new gene, sfaYII, coding for a putative phosphodiesterase that is located in between the sfaXII gene and the fimbrial biogenesis genes. Our studies by ectopic expression of sfaYII in Vibrio cholerae showed that the gene product caused reduced biofilm formation and it is proposed that sfaYII can influence cyclic-di-GMP turnover in the bacteria. Our findings demonstrate that the operons typical for S-fimbriae of extraintestinal pathogenic E. coli include previously unrecognized novel regulatory genes.

Place, publisher, year, edition, pages
Elsevier Ltd , 2009. Vol. 46, no 3, 150-158 p.
Keyword [en]
NMEC, Fimbrial genes, Regulation, sfaXII, sfaYII
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
Identifiers
URN: urn:nbn:se:umu:diva-22279DOI: 10.1016/j.micpath.2008.12.001PubMedID: 19103276OAI: oai:DiVA.org:umu-22279DiVA: diva2:214296
Available from: 2009-05-05 Created: 2009-05-04 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.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1266
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-22302 (URN)987-91-7264-789-3 (ISBN)
Distributor:
Molekylärbiologi (Medicinska fakulteten), 901 87, Umeå
Public defence
2009-05-28, Major Groove, Byggnad 6L, Institutionen för Molekylärbiologi, Umeå Universitet, Umeå, 10:00 (English)
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Available from: 2009-05-15 Created: 2009-05-05 Last updated: 2010-04-07Bibliographically approved

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Sondén, BeritWai, Sun NyuntUhlin, Bernt Eric

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Sjöström, Annika E.Sondén, BeritMüller, ClaudiaRydström, AnnaWai, Sun NyuntUhlin, Bernt Eric
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