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  • 51.
    Nakao, Ryoma
    et al.
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan.
    Myint, Si Lhyam
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Enhanced Biofilm Formation and Membrane Vesicle Release by Escherichia coli Expressing a Commonly Occurring Plasmid Gene, kil2018Ingår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 9, artikel-id 2605Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Escherichia coli is one of the most prevalent microorganisms forming biofilms on indwelling medical devices, as well as a representative model to study the biology and ecology of biofilms. Here, we report that a small plasmid gene, kil, enhances biofilm formation of E coli. The kil gene is widely conserved among naturally occurring colicinogenic plasmids such as ColE1 plasmid, and is also present in some plasmid derivatives used as cloning vectors. First, we found that overexpression of the kil gene product dramatically increased biofilm mass enriched with extracellular DNA in the outer membrane-compromised strain RN102, a deep rough LPS mutant E. coli K-12 derivative. We also found that the kil-enhanced biofilm formation was further promoted by addition of physiologically relevant concentrations of Mg2+, not only in the case of RN102, but also with the parental strain BW25113, which retains intact core-oligosaccharide LPS. Biofilm formation by kil-expressing BW25113 strain (BW25113 kil+) was significantly inhibited by protease but not DNase I. In addition, a large amount of proteinous materials were released from the BW25113 kil+ cells. These materials contained soluble cytoplasmic and periplasmic proteins, and insoluble membrane vesicles (MVs). The kil-induced MVs were composed of not only outer membrane/periplasmic proteins, but also inner membrane/cytoplasmic proteins, indicating that MVs from both of the outer and inner membranes could be released into the extracellular milieu. Subcellular fractionation analysis revealed that the Kil proteins translocated to both the outer and inner membranes in whole cells of BW25113 kil+. Furthermore, the BW25113 kil+ showed not only reduced viability in the stationary growth phase, but also increased susceptibility to killing by predator bacteria, Vibrio cholerae expressing the type VI secretion system, despite no obvious change in morphology and physiology of the bacterial membrane under regular culture conditions. Taken together, our findings suggest that there is risk of increasing biofilm formation and spreading of numerous MVs releasing various cellular components due to kil gene expression. From another point of view, our findings could also offer efficient MV production strategies using a conditional kil vector in biotechnological applications.

  • 52.
    Nakao, Ryoma
    et al.
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Enhanced biofilm formation by Escherichia coli LPS mutants defective in hep biosynthesis2012Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, nr 12, s. e51241-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lipopolysaccharide (LPS) is the major component of the surface of Gram-negative bacteria and its polysaccharide portion is situated at the outermost region. We investigated the relationship between the polysaccharide portion of LPS and biofilm formation using a series of Escherichia coli mutants defective in genes earlier shown to affect the LPS sugar compositions. Biofilm formation by a deep rough LPS mutant, the hldE strain, was strongly enhanced in comparison with the parental strain and other LPS mutants. The hldE strain also showed a phenotype of increased auto-aggregation and stronger cell surface hydrophobicity compared to the wild-type. Similar results were obtained with another deep rough LPS mutant, the waaC strain whose LPS showed same molecular mass as that of the hldE strain. Confocal laser scanning microscopy (CLSM) analysis and biofilm formation assay using DNase I revealed that biofilm formation by the hldE strain was dependent on extracellular DNA. Furthermore, a loss of flagella and an increase in amount of outer membrane vesicles in case of the hldE strain were also observed by transmission electron microscopy and atomic force microscopy, respectively. In addition, we demonstrated that a mutation in the hldE locus, which alters the LPS structure, caused changes in both expression and properties of several surface bacterial factors involved in biofilm formation and virulence. We suggest that the implication of these results should be considered in the context of biofilm formation on abiotic surfaces, which is frequently associated with nosocominal infections such as the catheter-associated infections.

  • 53. Osterblad, Monica
    et al.
    Karah, Nabil
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Halkilahti, Jani
    Sarkkinen, Hannu
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Jalava, Jari
    Rare Detection of the Acinetobacter Class D Carbapenemase bla(OXA-23) Gene in Proteus mirabilis2016Ingår i: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 60, nr 5, s. 3243-3245Artikel i tidskrift (Refereegranskat)
  • 54.
    Paracuellos, Patricia
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Öhman, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sauer-Eriksson, A Elisabeth
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Expression and purification of SfaX(II), a protein involved in regulating adhesion and motility genes in extraintestinal pathogenic Escherichia coli2012Ingår i: Protein Expression and Purification, ISSN 1046-5928, E-ISSN 1096-0279, Vol. 86, nr 2, s. 127-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pathogenic Escherichia coli strains commonly harbor genes involved in formation of fimbriae, such as the sfa(II) fimbrial gene cluster found in uropathogenic and newborn meningitis isolates. The sfaX(II) gene, located at the distal end of the sfa(II) operon, was recently shown to play a role in controlling virulence-related gene expression in extraintestinal pathogenic E. coli (ExPEC). Until now, detailed characterization of the SfaX(II) protein has been hampered by difficulties in obtaining large quantities of soluble protein. By a rational modeling approach, we engineered a Cys70Ser mutation, which successfully improved solubility of the protein. Here, we present the expression, purification, and initial characterization of the recombinant SfaX(IIC70S) mutant. The protein was produced in E. coli BL21 (DE3) cells grown in autoinduction culture media. The plasmid vector harbored DNA encoding the SfaX(IIC70S) protein N-terminally fused with a six histidine (H6) sequence followed by a ZZ tag (a derivative of the Staphylococcus protein A) (H6-ZZ tag). The H6-ZZ tag was cleaved off with Tobacco Etch Virus (TEV) protease and the 166 amino acid full-length homo-dimeric protein was purified using affinity and size-exclusion chromatography. Electrophoretic mobility gel shift assays and atomic force microscopy demonstrated that the protein possesses DNA-binding properties, suggesting that the transcriptional regulatory activity of SfaX(II) can be mediated via direct binding to DNA.

  • 55.
    Park, Hyun-Sook
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Östberg, Yngve
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Johansson, Jörgen
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Wagner, E Gerhart
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Novel role for a bacterial nucleoid protein in translation of mRNAs with suboptimal ribosome-binding sites2010Ingår i: Genes & Development, ISSN 0890-9369, E-ISSN 1549-5477, Vol. 24, nr 13, s. 1345-1350Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In Escherichia coli, the major nucleoid protein H-NS limits transcription by acting as a repressor or transcriptional silencer, presumably by its ability to close the looped chromosome domains in the nucleoid through DNA-protein-DNA bridging. Here, we demonstrate the direct involvement of H-NS as a positive factor stimulating translation of the malT mRNA. In vitro studies showed that H-NS facilitates a repositioning of the 30S preinitiation complex on the malT mRNA. H-NS stimulation of translation depended on the AU-rich -35 to -40 region of the mRNA. Several additional examples were found demonstrating a novel function for H-NS in translation of genes with suboptimal ribosome-binding sequences.

  • 56. Paytubi, Sònia
    et al.
    Madrid, Cristina
    Forns, Núria
    Nieto, José María
    Balsalobre, Carlos
    Uhlin, Bernt Eric
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten).
    Juárez, Antonio
    YdgT, the Hha paralogue in Escherichia coli, forms heteromeric complexes with H-NS and StpA.2004Ingår i: Mol Microbiol, ISSN 0950-382X, Vol. 54, nr 1, s. 251-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In enteric bacteria, proteins of the Hha/YmoA family play a role in the regulation of gene expression in response to environmental factors. Interaction of both Hha and YmoA with H-NS has been reported, and an Hha/H-NS complex has been shown to modulate expression in Escherichia coli of the haemolysin operon of plasmid pHly152. In addition to the hns gene, the chromosome of E. coli and other enteric bacteria also includes the stpA gene that encodes the StpA protein, an H-NS paralogue. We report here the identification of the Hha paralogue in E. coli, the YdgT protein. As Hha paralogue, YdgT appears to fulfil some of the functions reported for StpA as H-NS paralogue: YdgT is overexpressed in hha mutants and can compensate, at least partially, some of the hha-induced phenotypes. We also demonstrate that YdgT interacts both with H-NS and with StpA. Protein cross-linking studies showed that YdgT/H-NS heteromeric complexes are generated within the bacterial cell. The StpA protein, which is subjected to Lon-mediated turnover, was less stable in the absence of Hha or YdgT. Our findings suggest that Hha, YdgT and StpA may form complexes in vivo.

  • 57.
    Ramstedt, Madeleine
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nakao, Ryoma
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Nyunt Wai, Sun
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Monitoring surface chemistry changes in the bacterial cell wall: multivariate analysis of Cryo-X-ray photoelectron spectroscopy data2011Ingår i: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 286, nr 14, s. 12389-12396Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gram-negative bacteria can alter the composition of the Lipopolysaccharide (LPS) layer of the outer membrane as a response to different growth conditions and external stimuli. These alterations can, for example, promote attachment to surfaces and biofilm formation. The changes occur in the outermost layer of the cell and may consequently influence interactions between bacterial cells and surrounding host tissue, as well as other surfaces. Microscopic analyses, fractionation of bacterial cells or other traditional microbiological assays have previously been used to study these alterations. These methods can, however, be time consuming and do not always give detailed chemical information about the bacterial cell surface. We here present an analytical method that provides chemical information on the outermost portion of bacterial cells with respect to protein, peptidoglycan, lipid and polysaccharide content. The method involves cryo-X-ray Photoelectron Spectroscopy (XPS) analyses of the outermost portion (within ~10 nm of the surface) of intact bacterial cells, followed by a multivariate curve resolution analysis of carbon spectra. It can be used as a tool for characterizing and monitoring variations in the chemical composition of bacterial cell walls or of isolated outer membrane vesicles, variations that result from e.g. mutations or external stimuli. The method enabled us to accurately predict the alterations in polysaccharide content and surface chemistries of a set of well characterized Escherichia coli LPS mutants. The described approach may moreover be applied to monitor surface chemical composition of other biological samples.

  • 58.
    Rompikuntal, Pramod K.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Vdovikova, Svitlana
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Duperthuy, Marylise
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Johnson, Tanya L.
    Åhlund, Monika
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Lundmark, Richard
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Oscarsson, Jan
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Sandkvist, Maria
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Outer Membrane Vesicle-Mediated Export of Processed PrtV Protease from Vibrio cholerae2015Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 7, artikel-id e0134098Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background Outer membrane vesicles (OMVs) are known to release from almost all Gram-negative bacteria during normal growth. OMVs carry different biologically active toxins and enzymes into the surrounding environment. We suggest that OMVs may therefore be able to transport bacterial proteases into the target host cells. We present here an analysis of the Vibrio cholerae OMV-associated protease PrtV. Methodology/Principal Findings In this study, we demonstrated that PrtV was secreted from the wild type V. cholerae strain C6706 via the type II secretion system in association with OMVs. By immunoblotting and electron microscopic analysis using immunogold labeling, the association of PrtV with OMVs was examined. We demonstrated that OMV-associated PrtV was biologically active by showing altered morphology and detachment of cells when the human ileocecum carcinoma (HCT8) cells were treated with OMVs from the wild type V. cholerae strain C6706 whereas cells treated with OMVs from the prtV isogenic mutant showed no morphological changes. Furthermore, OMV-associated PrtV protease showed a contribution to bacterial resistance towards the antimicrobial peptide LL-37. Conclusion/Significance Our findings suggest that OMVs released from V. cholerae can deliver a processed, biologically active form of PrtV that contributes to bacterial interactions with target host cells.

  • 59.
    Rompikuntal, Pramod Kumar
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Åhlund, Monika
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Lindmark, Barbro
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Johnson, Tanya L
    Department of Microbiology and Immunology, University of Michigan Medical School..
    Sandkvist, Maria
    Department of Microbiology and Immunology, University of Michigan Medical School..
    Lundmark, Richard
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Outer membrane vesicle-mediated export of PrtV protease from Vibrio choleraeManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Background: Gram-negative bacteria release large amounts of outer membrane vesicles (OMVs) during normal growth. OMVs from pathogenic bacteria are known to carry different biologically active toxins and enzymes into the surrounding environment. We hypothesized that OMVs may therefore be able to mediate the transport of bacterial products into host cells. We present here an analysis of the V. cholerae OMV-associated virulence factor PrtV. 

    Methodology/Principal Findings: We observed that PrtV, a M6 family, zinc-binding metalloprotease, is secreted from V. cholerae wild type strain C6706 into the culture supernatant in association with OMVs. The association of PrtV with OMVs was determined by immunoblotting and electron microscopy using immunogold labeling. In addition, we observed that the PKD-domain(s) of PrtV has a role in the protein’s association with OMVs. We also demonstrated that OMV-associated PrtV was biologically active because HCT8 cells treated with OMVs from the wild type V. cholerae strain C6706 exhibited altered morphology, whereas cells treated with OMVs from the prtV isogenic mutant showed no morphological changes. Moreover, our data suggest that OMV-associated PrtV might be transported into target eukaryotic cells by a vesicle fusion mechanism in association with lipid raft microdomains in the plasma membrane.

    Conclusion/Significance: Our findings suggest that OMVs can deliver biologically active PrtV into target host cells.

  • 60.
    Ruhal, Rohit
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Antti, Henrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rzhepishevska, Olena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Barbero, David R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A multivariate approach to correlate bacterial surface properties to biofilm formation by lipopolysaccharide mutants of Pseudomonas aeruginosa2015Ingår i: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 127, nr 0, s. 182-191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract Bacterial biofilms are involved in various medical infections and for this reason it is of great importance to better understand the process of biofilm formation in order to eradicate or mitigate it. It is a very complex process and a large range of variables have been suggested to influence biofilm formation. However, their internal importance is still not well understood. In the present study, a range of surface properties of Pseudomonas aeruginosa lipopolysaccharide mutants were studied in relation to biofilm formation measured in different kinds of multi-well plates and growth conditions in order to better understand the complexity of biofilm formation. Multivariate analysis was used to simultaneously evaluate the role of a range of physiochemical parameters under different conditions. Our results suggest the presence of serum inhibited biofilm formation due to changes in twitching motility. From the multivariate analysis it was observed that the most important parameters, positively correlated to biofilm formation on two types of plates, were high hydrophobicity, near neutral zeta potential and motility. Negative correlation was observed with cell aggregation, as well as formation of outer membrane vesicles and exopolysaccharides. This work shows that the complexity of biofilm formation can be better understood using a multivariate approach that can interpret and rank the importance of different factors being present simultaneously under several different environmental conditions, enabling a better understanding of this complex process.

  • 61.
    Römling, U.
    et al.
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, S-17177 Stockholm, Sweden.
    Kjelleberg, S.
    Singapore Ctr Environm Life Sci Engn, Singapore, Singapore.
    Normark, S.
    Karolinska Inst, Dept Microbiol Tumor & Cell Biol, S-17177 Stockholm, Sweden.
    Nyman, L.
    Pfizer AB, Stockholm, Sweden.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Åkerlund, B.
    Karolinska Univ Hosp, Dept Med Huddinge, Infect Dis Unit, Stockholm, Sweden.
    Microbial biofilm formation: a need to act2014Ingår i: Journal of Internal Medicine, ISSN 0954-6820, E-ISSN 1365-2796, Vol. 276, nr 2, s. 98-110Artikel i tidskrift (Refereegranskat)
  • 62.
    Singh, Bhupender
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mortezaei, Narges
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Savarino, Stephen J.
    Enteric Diseases Department, Naval Medical Research Center, Silver Spring, MD, 20910, USA.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Bullitt, Esther
    Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118, USA.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Antibodies damage the resilience of fimbriae, causing them to be stiff and tangled2017Ingår i: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 199, nr 1, artikel-id e00665-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As adhesion fimbriae are a major virulence factor for many pathogenic Gram-negative bacteria, they are also potential targets for antibodies. Fimbriae are commonly required for initiating the colonization that leads to disease, and their success as adhesion organelles lies in their ability to both initiate and sustain bacte- rial attachment to epithelial cells. The ability of fimbriae to unwind and rewind their helical filaments presumably reduces their detachment from tissue surfaces with the shear forces that accompany significant fluid flow. Therefore, the disruption of func- tional fimbriae by inhibiting this resilience should have high potential for use as a vaccine to prevent disease. In this study, we show that two characteristic biome- chanical features of fimbrial resilience, namely, the extension force and the exten- sion length, are significantly altered by the binding of antibodies to fimbriae. The fimbriae that were studied are normally expressed on enterotoxigenic Escherichia coli, which are a major cause of diarrheal disease. This alteration in biomechanical properties was observed with bivalent polyclonal antifimbrial antibodies that recog- nize major pilin subunits but not with the Fab fragments of these antibodies. Thus, we propose that the mechanism by which bound antibodies disrupt the uncoiling of natural fimbria under force is by clamping together layers of the helical filament, thereby increasing their stiffness and reducing their resilience during fluid flow. In addition, we propose that antibodies tangle fimbriae via bivalent binding, i.e., by binding to two individual fimbriae and linking them together. Use of antibodies to disrupt physical properties of fimbriae may be generally applicable to the large number of Gram-negative bacteria that rely on these surface-adhesion molecules as an essential virulence factor.

    I M P O R T A N C E Our study shows that the resiliency of colonization factor antigen I (CFA/I) and coli surface antigen 2 (CS2) fimbriae, which are current targets for vac- cine development, can be compromised significantly in the presence of antifimbrial antibodies. It is unclear how the humoral immune system specifically interrupts in- fection after the attachment of enterotoxigenic Escherichia coli (ETEC) to the epithe- lial surface. Our study indicates that immunoglobulins, in addition to their well- documented role in adaptive immunity, can mechanically damage the resilience of fimbriae of surface-attached ETEC, thereby revealing a new mode of action. Our data suggest a mechanism whereby antibodies coat adherent and free-floating bacteria to impede fimbrial resilience. Further elucidation of this possible mechanism is likely to inform the development and refinement of preventive vaccines against ETEC diar- rhea. 

  • 63.
    Singh, Bhupender
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mortezaei, Narges
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Savarino, Stephen
    Bullitt, Esther
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Antibody-mediated disruption of the mechanics of CS20 fimbriae of enterotoxigenic Escherichia coli2015Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, artikel-id 13678Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Preventive vaccines against enterotoxigenic Escherichia coli (ETEC) are being developed, many of which target common fimbrial colonization factors as the major constituent, based on empirical evidence that these function as protective antigens. Particularly, passive oral administration of ETEC anti-fimbrial antibodies prevent ETEC diarrhea. Little is, however, known regarding the specific mechanisms by which intestinal antibodies against ETEC fimbriae function to prevent disease. Using coli surface antigen 20 (CS20) fimbriae as a model ETEC colonization factor, we show using force spectroscopy that anti-fimbrial antibodies diminish fimbrial elasticity by inhibiting their natural capacity to unwind and rewind. In the presence of anti-CS20 antibodies the force required to unwind a single fimbria was increased several-fold and the extension length was shortened several-fold. Similar measurements in the presence of anti-CS20 Fab fragments did not show any effect, indicating that bivalent antibody binding is required to reduce fimbrial elasticity. Based on these findings, we propose a model for an in-vivo mechanism whereby antibody-mediated disruption of the biomechanical properties of CS20 fimbriae impedes sustained adhesion of ETEC to the intestinal mucosal surface. Further elucidation of the role played by intestinal antibodies in mechanical disruption of fimbrial function may provide insights relevant to ETEC vaccine development.

  • 64.
    Sjöström, Annika E.
    et al.
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinsk fakultet, Molekylär Infektionsmedicin, Sverige (MIMS).
    Balsalobre, Carlos
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinsk fakultet, Molekylär Infektionsmedicin, Sverige (MIMS).
    Emödy, Levente
    Department of Medical Microbiology and Immunology, University medical School, Pecs, Hungary.
    Westerlund-Wikström, Benita
    General Microbiology, Faculty of Biosciences, University of Helsinki, Finland.
    Hacker, Jörg
    Robert-Koch-Institut, Nordufer, Berlin, Germany.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinsk fakultet, Molekylär Infektionsmedicin, Sverige (MIMS).
    The SfaXII protein from newborn meningitis E. coli is involved in regulation of motility and type 1 fimbriae expression2009Ingår i: Microbial Pathogenesis, ISSN 0882-4010, E-ISSN 1096-1208, Vol. 46, nr 5, s. 243-252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The genomes of pathogenic E. coli may contain several different fimbrial operons. How bacteria regulate and coordinate the choice of fimbrial expression under different circumstances remains largely unanswered. In this report we have investigated the role of the sfaXII gene associated to the SfaII fimbrial determinant in the E. coli isolate IHE3034. sfaXII belongs to a subfamily of genes, the 17kDa genes, located near different fimbrial operons in uropathogenic and newborn meningitis E. coli (NMEC) strains. Using the NMEC isolate IHE3034 and non-pathogenic E. coli strains we found that the sfaXII gene had an inhibitory effect on type 1 fimbriae expression. Down regulation of type 1 fimbriae was exerted at transcriptional level both by inhibiting expression from the fimA promoter and by reducing the frequency of OFF-to-ON switching. The effect of sfaXII on expression of the recombinase FimB that catalyzes OFF to ON switching might explain the described reduction in percentage of ON cells. Moreover, expression of the sfaXII gene strongly influenced motility and flagella production of the NMEC isolate IHE3034. We propose that the sfaXII gene, and presumably other members in the 17kDa gene family, may play a role in the control of virulence related gene expression in pathogenic E. coli.

  • 65.
    Sjöström, Annika E
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Sandblad, Linda
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Membrane vesicle-mediated release of bacterial RNA2015Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, artikel-id 15329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many Gram-negative bacterial species release outer membrane vesicles (OMVs) that interact with the host by delivering virulence factors. Here, we report for the first time that RNA is among the wide variety of bacterial components that are associated with OMVs. To characterize the RNA profiles of bacterial OMVs, we performed RNA deep sequencing analysis using OMV samples isolated from a wild type Vibrio cholerae O1 El Tor strain. The results showed that RNAs originating from intergenic regions were the most abundant. Our findings reveal a hitherto unrecognised feature of OMVs mimicking eukaryotic exosomes and highlight a need to evaluate the potential role of RNA-containing bacterial membrane vesicles in bacteria-host interactions.

  • 66.
    Sjöström, Annika E.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Sondén, Berit
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Müller, Claudia
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Rydström, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Dobrindt, Ulrich
    Institute for Molecular Infection Biology, University of Würzburg, Germany.
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    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 operon2009Ingår i: Microbial Pathogenesis, ISSN 0882-4010, E-ISSN 1096-1208, Vol. 46, nr 3, s. 150-158Artikel i tidskrift (Refereegranskat)
    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.

  • 67.
    Sjöström, Annika E
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Growth phase regulated expression of sfaXII is negatively influenced by the RpoS sigma factor and the Hfq RNA chaperoneManuskript (Övrigt vetenskapligt)
    Abstract [en]

    The regulatory gene sfaXII in the S fimbrial gene cluster of the newborn meningitis E. coli isolate IHE3034 is expressed in a growth phase dependent fashion with the highest levels at the onset of the stationary phase. It is then mainly transcribed from a promoter proximal to the gene. We have assessed the potential influence by the stationary phase sigma factor, σS, in the sfaXII regulation. In contrast to the stimulatory role commonly seen with stationary phase induced genes, we found that σS exerted a strong repressive effect on sfaXII transcription. Tests with an hfq mutant strain suggested that also the RNA chaperon Hfq caused negative regulation of sfaXII transcription. In both cases the effects were considered indirect via some other regulatory factor(s). Results from a transposon insertion mutagenesis experiment indicated that it may be possible to identify additional genes involved in sfaXII regulation.

  • 68.
    Song, Tianyan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Sabharwal, Dharmesh
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Gurung, Jyoti Mohan
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Cheng, Andrew T.
    Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, United States of America.
    Sjöström, Annika E.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Yildiz, Fitnat H.
    Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, United States of America.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Vibrio cholerae Utilizes Direct sRNA Regulation in Expression of a Biofilm Matrix Protein2014Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, nr 7, artikel-id e101280Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrio cholerae biofilms contain exopolysaccharide and three matrix proteins RbmA, RbmC and Bap1. While much is known about exopolysaccharide regulation, little is known about the mechanisms by which the matrix protein components of biofilms are regulated. VrrA is a conserved, 140-nt sRNA of V. cholerae, whose expression is controlled by sigma factor sigma(E). In this study, we demonstrate that VrrA negatively regulates rbmC translation by pairing to the 5' untranslated region of the rbmC transcript and that this regulation is not stringently dependent on the RNA chaperone protein Hfq. These results point to VrrA as a molecular link between the sigma(E)-regulon and biofilm formation in V. cholerae. In addition, VrrA represents the first example of direct regulation of sRNA on biofilm matrix component, by-passing global master regulators.

  • 69. Söderblom, Tomas
    et al.
    Oxhamre, Camilla
    Wai, Sun Nyunt
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten).
    Uhlén, Per
    Aperia, Anita
    Uhlin, Bernt Eric
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten).
    Richter-Dahlfors, Agneta
    Effects of the Escherichia coli toxin cytolysin A on mucosal immunostimulation via epithelial Ca2+ signalling and Toll-like receptor 4.2005Ingår i: Cell Microbiol, ISSN 1462-5814, Vol. 7, nr 6, s. 779-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Epithelial cells are vital to sense the presence of bacteria, thereby initiating a proper innate immune response. This occurs via different mechanisms, e.g. recognition by pattern recognition receptors (TLR), or alteration of the cellular Ca2+ homeostasis. The Escherichia coli toxin cytolysin A (ClyA) is naturally delivered to target cells as active pore assemblies within outer membrane vesicles (OMVs), and we here investigate a possible role of ClyA-containing OMVs (ClyA+ (OMV)) for induction of proinflammatory responses via the above-mentioned mechanisms. We report that low, sublytic concentrations of ClyA+ (OMV) affect the Ca2+ homeostasis in epithelial cells by induction of slow, intracellular Ca2+ oscillations, while increased concentrations act cytolytically. Thus, ClyA belongs to the novel group of pore-forming toxins shown to elicit such biphasic responses. Ca2+ waves in the minute range have been shown to regulate gene transcription of, e.g. interleukin (IL)-6 and -8. While the periodicity of ClyA+ (OMV)-induced Ca2+ waves (22.9 +/- 0.9 min) fail to induce an IL-8 response, our data fit to the general concept of frequency-specific gene expression. Molecular investigations of the signal transduction pathway reveals that ClyA+ (OMV) utilize a different one as compared with those previously reported for other toxins causing Ca2+ waves. The ClyA protein per se and ClyA pore assemblies are non-immunogenic, while lipopolysaccharide present on the OMVs induces a TLR4-dependent proinflammatory response as expected. Additional membrane components of the OMV, e.g. OmpW, was also found to elicit proinflammatory responses that was independent of TLR4 and Ca2+ signalling.

  • 70.
    Wai, Sun Nyunt
    et al.
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten).
    Lindmark, Barbro
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten).
    Söderblom, Tomas
    Takade, Akemi
    Westermark, Marie
    Oscarsson, Jan
    Jass, Jana
    Richter-Dahlfors, Agneta
    Mizunoe, Yoshimitsu
    Uhlin, Bernt Eric
    Umeå universitet, Medicinsk fakultet, Molekylärbiologi (Medicinska fakulteten).
    Vesicle-mediated export and assembly of pore-forming oligomers of the enterobacterial ClyA cytotoxin.2003Ingår i: Cell, ISSN 0092-8674, Vol. 115, nr 1, s. 25-35Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ClyA protein is a pore-forming cytotoxin expressed by Escherichia coli and some other enterobacteria. It confers cytotoxic activity toward mammalian cells, but it has remained unknown how ClyA is surface exposed and exported from bacterial cells. Outer-membrane vesicles (OMVs) released from the bacteria were shown to contain ClyA protein. ClyA formed oligomeric pore assemblies in the OMVs, and the cytotoxic activity toward mammalian cells was considerably higher than that of ClyA protein purified from the bacterial periplasm. The redox status of ClyA correlated with its ability to form the oligomeric pore assemblies. In bacterial cells with a defective periplasmic disulphide oxidoreductase system, the ClyA protein was phenotypically expressed in a constitutive manner. The results define a vesicle-mediated transport mechanism in bacteria, and our findings show that the localization of proteins to OMVs directly may contribute to the activation and delivery of pathogenic effector proteins.

  • 71.
    Wikström Hultdin, Ulrika
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lindberg, Stina
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Grundström, Christin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Allgardsson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Huang, Shenghua
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Stier, Günter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Öhman, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Sauer-Eriksson, Elisabeth
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Purification, crystallization and preliminary data analysis of FocB, a transcription factor regulating fimbrial adhesin expression in uropathogenic Escherichia coli2010Ingår i: Acta Crystallographica. Section F: Structural Biology and Crystallization Communications, ISSN 1744-3091, E-ISSN 1744-3091, Vol. 66, nr Pt 3, s. 337-341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The transcription factor FocB belongs to a family of regulators encoded by several different fimbriae gene clusters in uropathogenic Escherichia coli. Recent findings suggest that FocB-family proteins may form different protein-protein complexes and that they may exert both positive and negative effects on the transcription of fimbriae genes. However, little is known about the actual role and mode of action when these proteins interact with the fimbriae operons. The 109-amino-acid FocB transcription factor from the foc gene cluster in E. coli strain J96 has been cloned, expressed and purified. The His6-tagged fusion protein was captured by Ni2+-affinity chromatography, cleaved with tobacco etch virus protease and purified by gel filtration. The purified protein is oligomeric, most likely in the form of dimers. NMR analysis guided the crystallization attempts by showing that probable conformational exchange or oligomerization is reduced at temperatures above 293 K and that removal of the highly flexible His6 tag is advantageous. The protein was crystallized using the hanging-drop vapour-diffusion method at 295 K. A native data set to 2.0 Å resolution was collected at 100 K using synchrotron radiation.

  • 72.
    Wikström Hultdin, Ulrika
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lindberg, Stina
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Grundström, Christin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Huang, Shenghua
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Sauer-Eriksson, Elisabeth
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Structure of FocB: a member of a family of transcription factors regulating fimbrial adhesin expression in uropathogenic Escherichia coli2010Ingår i: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 277, nr 16, s. 3368-3381Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In uropathogenic Escherichia coli, UPEC, different types of fimbriae are expressed in order to mediate interactions with host tissue. FocB belongs to the PapB family of transcription factors involved in the regulation of fimbriae gene clusters. Recent findings suggest that members from this family of proteins may form different protein-protein complexes and that they may exert both positive and negative effects on transcription of fimbriae genes. To elucidate the detailed function of FocB, we have determined its crystal structure at 1.4 Å resolution. FocB is an all alpha helical structure with a helix-turn-helix (HTH) motif. Interestingly, conserved residues important for DNA-binding are not located in the recognition helix of the HTH-motif, but in the preceding helix. Results from protein-DNA binding studies indicated that FocB interacts with minor groove of its cognate DNA, which also points to a DNA-interaction unusual for this motif. Packing interactions in the crystals gave two plausible dimerization interfaces. Conserved residues known to be important for protein oligomerization are present at both interfaces, suggesting that both sites play a role in a functional FocB protein.

  • 73.
    Zhang, Zhen
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Aung, Kyaw Min
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Reversible senescence of human colon cancer cells after blockage of mitosis/cytokinesis caused by the CNF1 cyclomodulin from Escherichia coli2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 17780Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cytotoxic necrotizing factor 1 (CNF1), a protein toxin produced by extraintestinal pathogenic Escherichia coli, activates the Rho-family small GTPases in eukaryotic cell, thereby perturbing multiple cellular functions. Increasing epidemiological evidence suggests a link between CNF1 and human inflammatory bowel disease and colorectal cancer. At the cellular level, CNF1 has been hypothesized to reprogram cell fate towards survival due to the role in perturbing cell cycle and apoptosis. However, it remains undetermined how cells survive from CNF1 intoxication. In this work, we show that CNF1 treatment blocks mitosis/cytokinesis, elicits endoreplication and polyploidisation in cultured human colon cancer cells, and drives them into reversible senescence, which provides a survival route for cells via depolyploidisation. Senescence in CNF1-treated cells is demonstrated with upregulation of several senescence markers including senescence-associated β-galactosidase activity, p53, p21 and p16, and concomitant inhibition of the retinoblastoma protein phosphorylation. Importantly, progeny derived from CNF1 treatment exhibit genomic instability exemplified by increased aneuploidy and become more resistant to CNF1, but not to 5-fluorouracil and oxaliplatin, the two agents commonly used in chemotherapeutic treatment for colorectal cancer. These observations display survival features of the cell after CNF1 treatment that may have implications for the potential role of CNF1 in carcinogenesis.

  • 74.
    Zlatkov, Nikola
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Absence of Global Stress Regulation in Escherichia coli Promotes Pathoadaptation and Novel c-di-GMP-dependent Metabolic Capability2019Ingår i: Scientific Reports, ISSN 2045-2322, Vol. 9, artikel-id 2600Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    athoadaptive mutations linked to c-di-GMP signalling were investigated in neonatal meningitis-causing Escherichia coli (NMEC). The results indicated that NMEC strains deficient in RpoS (the global stress regulator) maintained remarkably low levels of c-di-GMP, a major bacterial sessility-motility switch. Deletion of ycgG2, shown here to encode a YcgG allozyme with c-di-GMP phosphodiesterase activity, and the restoration of RpoS led to a decrease in S-fimbriae, robustly produced in artificial urine, hinting that the urinary tract could serve as a habitat for NMEC. We showed that NMEC were skilled in aerobic citrate utilization in the presence of glucose, a property that normally does not exist in E. coli. Our data suggest that this metabolic novelty is a property of extraintestinal pathogenic E. coli since we reconstituted this ability in E. coli UTI89 (a cystitis isolate) via deactivation rpoS; additionally, a set of pyelonephritis E. coli isolates were shown here to aerobically use citrate in the presence of glucose. We found that the main reason for this metabolic capability is RpoS inactivation leading to the production of the citrate transporter CitT, exploited by NMEC for ferric citrate uptake dependent on YcgG2 (an allozyme with c-di-GMP phosphodiesterase activity).

  • 75.
    Zlatkov, Nikola
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    C-di-GMP-mediated Morphotypic Pathoadaptability of Neonatal Meningitis Escherichia coliManuskript (preprint) (Övrigt vetenskapligt)
  • 76.
    Åberg, Veronica
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Fällman, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Hultgren, Scott J.
    Department of Molecular Microbiology, Washington University in St. Louis School of Medicine, St. Louis,USA.
    Almqvist, Fredrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Pilicides regulate pili expression in E. coli without affecting the functional properties of the pilus rod2007Ingår i: Molecular BioSystems, ISSN 1742-206X, Vol. 3, s. 214-218Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The infectious ability of uropathogenic Escherichia coli relies on adhesive fibers, termed pili or fimbriae, that are expressed on the bacterial surface. Pili are multi-protein structures that are formed via a highly preserved assembly and secretion system called the chaperone-usher pathway. We have earlier reported that small synthetic compounds, referred to as pilicides, disrupt both type 1 and P pilus biogenesis in E. coli. In this study, we show that the pilicides do not affect the structure, dynamics or function of the pilus rod. This was demonstrated by first suppressing the expression of P pili in E. coli by pilicide treatment and, next, measuring the biophysical properties of the pilus rod. The reduced abundance of pili was assessed with hemagglutination, atomic force microscopy and Western immunoblot analysis. The biodynamic properties of the pili fibers were determined by optical tweezers force measurements on individual pili and were found to be intact. The presented results establish a potential use of pilicides as chemical tools to study important biological processes e.g. adhesion, pilus biogenesis and the role of pili in infections and biofilm formation.

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