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  • 51. Bengtsson-Palme, Johan
    et al.
    Angelin, Martin
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Huss, Mikael
    Kjellqvist, Sanela
    Kristiansson, Erik
    Palmgren, Helena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Larsson, D. G. Joakim
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    The Human Gut Microbiome as a Transporter of Antibiotic Resistance Genes between Continents2015Ingår i: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 59, nr 10, s. 6551-6560Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Previous studies of antibiotic resistance dissemination by travel have, by targeting only a select number of cultivable bacterial species, omitted most of the human microbiome. Here, we used explorative shotgun metagenomic sequencing to address the abundance of >300 antibiotic resistance genes in fecal specimens from 35 Swedish students taken before and after exchange programs on the Indian peninsula or in Central Africa. All specimens were additionally cultured for extended-spectrum beta-lactamase (ESBL)-producing enterobacteria, and the isolates obtained were genome sequenced. The overall taxonomic diversity and composition of the gut microbiome remained stable before and after travel, but there was an increasing abundance of Proteobacteria in 25/35 students. The relative abundance of antibiotic resistance genes increased, most prominently for genes encoding resistance to sulfonamide (2.6-fold increase), trimethoprim (7.7-fold), and beta-lactams (2.6-fold). Importantly, the increase observed occurred without any antibiotic intake. Of 18 students visiting the Indian peninsula, 12 acquired ESBL-producing Escherichia coli, while none returning from Africa were positive. Despite deep sequencing efforts, the sensitivity of metagenomics was not sufficient to detect acquisition of the low-abundant genes responsible for the observed ESBL phenotype. In conclusion, metagenomic sequencing of the intestinal microbiome of Swedish students returning from exchange programs in Central Africa or the Indian peninsula showed increased abundance of genes encoding resistance to widely used antibiotics.

  • 52.
    Bergström, Sven
    Umeå universitet, Medicinska fakulteten, Mikrobiologi.
    Chromosomal β-lactamases in enterobacteria and in vivo evolution of β-lactam resistance1983Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The ß-lactam antibiotics are the most important antibacterial agents in the treatment of infectious diseases. A severe problem in ß-lactam therapy is the emergence of ß-lactam resistant bacteria. Clinical ß-lactam resistance is most often due to the production of ß-lactamases. ß-lactamase genes reside either on plasmids or on the chromosome. The aim of this study was to acquire an understanding of organisation and regulation of chromosomal ß- lactamase genes in different Gram negative species and to elucidate the mechanisms for ampC hyperproduction in the in vivo situation.

    By DNA hybridization with an ampC probe from Escherichia coli K-12 it was shown that other Gram negative bacteria contained an artpC like chromosomal gene, suggesting a common evolutionary origin. Furthermore, the preceding frd operon that overlaps the ampC gene in E. coli K-12 was found to be much more conserved than the ampC gene in the bacterial species investigated.

    The ampC and frd opérons in Shigella sonnei and Citrobacter freundii were cloned and characterized by physical mapping. The respective maps were compared to the ampC and frd region in E. coli K-12. The physical map of Sh. sonnei was almost identical to the E. coli K-12 map, whereas in C. freundii only the frd region exhibited any considerable homology. Moreover, in C. freundii, the anpC and frd regions were separated by 1100 basepairs. It is suggested that this DNA is involved in the induction of ß-lactamase production in this organism. A hypothesis for the evolution of the anpC operon in enterobacteria is presented.

    By isolating and characterizing six ß-lactam resistant clinica], isolates of E. coli hyperproducing the dhrcmosomal ß-lactamase, genetic mechanisms for in vivo evolved resistance was aimed at. These isolates exhibited a 24-48 fold increase in ß-lactamase production. The ß-lactamase produced was found to be biochemically and immunologically identical to the ß-lactamase produced by E. coli K-12. The ampC control region of these six E. coli isolates was DNA-seqenced. The cause of ß-lactamase hyperproduction in five of the clinical E. coli isolates, identical in the DNA segment sequenced, was due to a strong novel ampC promoter displaced 5 bp upstream of the ampC promoter defined in E. coli K-12. The ß-lactamase hyperproduction in the sixth clinical isolate was shown to be caused by two mutations affecting both the promoter and the attenuator in the regulatory region defined by E. coli K- 12. The obtained changes were sufficient to explain the increase in ampC ß- 1 act ama se expression exhibited in these clinical E. coli isolates.

    Sequence analysis of the ampC control region in Sh. sonnei revealed that it was, with one exception, identical to the one found in the five clinical E. coli ß-lactamase hyperproducers. The only difference was in a position that creates the strong novel ampC promoter in the E. coli hyperproducers. By isolating spontaneous Sh. sonnei mutants with a 40-fold increase in ß-lactamase production carrying the same novel ampC promoter as the clinical E. coli isolates it was concluded that this DNA segment has been transferred in vivo frcm Shigella to E. coli across the species barrier.

  • 53.
    Bernardo-Garcia, Noelia
    et al.
    Department of Crystallography and Structural Biology, Instituto de Química Física "Rocasolano", CSIC, Madrid, Spain.
    Sanchez-Murcia, Pedro
    Univ Alcala De Henares, Area Farmacol, Dept Ciencias Biomed, Unidad Asociada I D I,CSIC, Madrid, Spain.
    Gago, Federico
    Univ Alcala De Henares, Area Farmacol, Dept Ciencias Biomed, Unidad Asociada I D I,CSIC, Madrid, Spain.
    Cava, Felipe
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Hermoso, Juan A.
    CSIC, Inst Quim Fis Rocasolano, Dept Crystallog & Struct Chem, Madrid, Spain.
    Structural Bioinformatics in Broad-Spectrum Racemases: a new path in anti-microbial research2016Ingår i: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 20, nr 11, s. 1222-1231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    D-amino acids are essential components of the bacterial cell wall and play notable roles in microbiology as regulators, for example in sporulation, biofilm formation or interspecies communication. Racemases are the specific enzymes catalyzing the interconversion of L-amino acids to D-amino acids. While most of racemases are mono-specific, a family of broad-spectrum racemases that can racemize ten of the 19 natural chiral amino acids has been recently reported. These enzymes can interconvert radically different residues such as aliphatic and positively charged residues producing non-canonical D-amino acids. Crystal structures together with bioinformatics allowed identification of the residues defining the molecular footprint in broad-spectrum racemases, the specific features of their active sites and the structural basis of their promiscuity. Here we review the recent knowledge on this family compared with the well established of alanine racemases. This structural information is a prerequisite for the development of novel drugs against the important human pathogens for which broad-spectrum racemases play a key role.

  • 54. Berthelot, Claire C
    et al.
    Kamita, Shizuo George
    Sacchi, Romina
    Yang, Jun
    Nording, Malin L
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Entomology, University of California Davis, Davis, CA, United States Of America.
    Georgi, Katrin
    Karbowski, Christine Hegedus
    German, J Bruce
    Weiss, Robert H
    Hogg, Ronald J
    Hammock, Bruce D
    Zivkovic, Angela M
    Changes in PTGS1 and ALOX12 Gene Expression in Peripheral Blood Mononuclear Cells Are Associated with Changes in Arachidonic Acid, Oxylipins, and Oxylipin/Fatty Acid Ratios in Response to Omega-3 Fatty Acid Supplementation2015Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 12, artikel-id e0144996Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Introduction: There is a high degree of inter-individual variability among people in response to intervention with omega-3 fatty acids (FA), which may partly explain conflicting results on the effectiveness of omega-3 FA for the treatment and prevention of chronic inflammatory diseases. In this study we sought to evaluate whether part of this inter-individual variability in response is related to the regulation of key oxylipin metabolic genes in circulating peripheral blood mononuclear cells (PBMCs). Methods: Plasma FA and oxylipin profiles from 12 healthy individuals were compared to PBMC gene expression profiles following six weeks of supplementation with fish oil, which delivered 1.9 g/d eicosapentaenoic acid (EPA) and 1.5 g/d docosahexaenoic acid (DHA). Fold changes in gene expression were measured by a quantitative polymerase chain reaction (qPCR). Results: Healthy individuals supplemented with omega-3 FA had differential responses in prostaglandin-endoperoxide synthase 1 (PTGS1), prostaglandin-endoperoxide synthase 2 (PTGS2), arachidonate 12-lipoxygenase (ALOX12), and interleukin 8 (IL-8) gene expression in isolated PBMCs. In those individuals for whom plasma arachidonic acid (ARA) in the phosphatidylethanolamine (PE) lipid class decreased in response to omega-3 intervention, there was a corresponding decrease in gene expression for PTGS1 and ALOX12. Several oxylipin product/FA precursor ratios (e.g. prostaglandin E-2 (PGE(2))/ARA for PTGS1 and 12-hydroxyeicosatetraenoic acid (12-HETE)/ARA for ALOX12) were also associated with fold change in gene expression, suggesting an association between enzyme activity and gene expression. The fold-change in PTGS1 gene expression was highly positively correlated with ALOX12 gene expression but not with PTGS2, whereas IL-8 and PTGS2 were positively correlated. Conclusions: The regulation of important oxylipin metabolic genes in PBMCs varied with the extent of change in ARA concentrations in the case of PTGS1 and ALOX12 regulation. PBMC gene expression changes in response to omega-3 supplementation varied among healthy individuals, and were associated with changes in plasma FA and oxylipin composition to different degrees in different individuals.

  • 55. Bianchi, Matteo
    et al.
    Niemiec, Maria J
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Siler, Ulrich
    Urban, Constantin F.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Reichenbach, Janine
    Restoration of anti-Aspergillus defense by neutrophil extracellular traps in human chronic granulomatous disease after gene therapy is calprotectin-dependent2011Ingår i: Journal of Allergy and Clinical Immunology, ISSN 0091-6749, E-ISSN 1097-6825, Vol. 127, nr 5, s. 1243-1252 e.7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND: Aspergillus spp infection is a potentially lethal disease in patients with neutropenia or impaired neutrophil function. We showed previously that Aspergillus hyphae, too large for neutrophil phagocytosis, are inhibited by reactive oxygen species-dependent neutrophil extracellular trap (NET) formation. This process is defective in chronic granulomatous disease (CGD) because of impaired phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase function.

    OBJECTIVE: To determine the antifungal agent and mechanism responsible for reconstitution of Aspergillus growth inhibition within NETs after complementation of NADPH oxidase function by gene therapy (GT) for CGD.

    METHODS: Antifungal activity of free and NET-released calprotectin was assessed by incubation of Aspergillus nidulans with purified calprotectin, induced NETs from human controls, and CGD neutrophils after GT in the presence or absence of Zn(2+) or alpha-S100A9 antibody, and with induced NETs from wild-type or S100A9(-/-) mouse neutrophils.

    RESULTS: We identified the host Zn(2+) chelator calprotectin as a neutrophil-associated antifungal agent expressed within NETs, reversibly preventing A nidulans growth at low concentrations, and leading to irreversible fungal starvation at higher concentrations. Specific antibody-blocking and Zn(2+) addition abolished calprotectin-mediated inhibition of A nidulans proliferation in vitro. The role of calprotectin in anti-Aspergillus defense was confirmed in calprotectin knockout mice.

    CONCLUSION: Reconstituted NET formation by GT for human CGD was associated with rapid cure of pre-existing therapy-refractory invasive pulmonary aspergillosis in vivo, underlining the role of functional NADPH oxidase in NET formation and calprotectin release for antifungal activity. These results demonstrate the critical role of calprotectin in human innate immune defense against Aspergillus infection.

  • 56.
    Billker, Oliver
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    CRISPRing the elephant in the room2018Ingår i: Cell Host and Microbe, ISSN 1931-3128, E-ISSN 1934-6069, Vol. 24, nr 6, s. 754-755Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The importance of guanylyl-cyclases (GCs) in apicomplexa has remained elusive due to the large size of the genes. Two recent studies, including Brown and Sibley, 2018 in this issue of Cell Host & Microbe, make elegant use of genome editing with CRISPR-Cas9 to characterize roles of GCs in Toxoplasma and Plasmodium.

  • 57. Birdsell, Dawn N
    et al.
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Öhrman, Caroline
    Swedish Defense Research Agency, Umeå.
    Kaufman, Emily
    Molins, Claudia
    Pearson, Talima
    Gyuranecz, Miklós
    Naumann, Amber
    Vogler, Amy J
    Myrtennäs, Kerstin
    Swedish Defense Research Agency, Umeå.
    Larsson, Pär
    Swedish Defense Research Agency, Umeå.
    Forsman, Mats
    Swedish Defense Research Agency, Umeå.
    Sjödin, Andreas
    Swedish Defense Research Agency, Umeå.
    Gillece, John D
    Schupp, James
    Petersen, Jeannine M
    Keim, Paul
    Wagner, David M
    Francisella tularensis subsp. tularensis group A.I, United States2014Ingår i: Emerging Infectious Diseases, ISSN 1080-6040, E-ISSN 1080-6059, Vol. 20, nr 5, s. 861-865Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We used whole-genome analysis and subsequent characterization of geographically diverse strains using new genetic signatures to identify distinct subgroups within Francisella tularensis subsp. tularensis group A.I: A.I.3, A.I.8, and A.I.12. These subgroups exhibit complex phylogeographic patterns within North America. The widest distribution was observed for A.I.12, which suggests an adaptive advantage.

  • 58. Birgand, G.
    et al.
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Szilagyi, E.
    Lucet, J. -C
    Overcoming the obstacles of implementing infection prevention and control guidelines2015Ingår i: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 21, nr 12, s. 1067-1071Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Reasons for a successful or unsuccessful implementation of infection prevention and control (IPC) guidelines are often multiple and interconnected. This article reviews key elements from the national to the individual level that contribute to the success of the implementation of IPC measures and gives perspectives for improvement. Governance approaches, modes of communication and formats of guidelines are discussed with a view to improve collaboration and transparency among actors. The culture of IPC influences practices and varies according to countries, specialties and healthcare providers. We describe important contextual aspects, such as relationships between actors and resources and behavioural features including professional background or experience. Behaviour change techniques providing goal-setting, feedback and action planning have proved effective in mobilizing participants and may be key to trigger social movements of implementation. The leadership of international societies in coordinating actions at international, national and institutional levels using multidisciplinary approaches and fostering collaboration among clinical microbiology, infectious diseases and IPC will be essential for success. Clinical Microbiology and Infection (C) 2015 European Society of Clinical Microbiology and Infectious Diseases. 

  • 59.
    Bitar, Aziz
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Immunologi/immunkemi.
    De, Rituparna
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Immunologi/immunkemi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Melgar, Silvia
    Aung, Kyaw Min
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Immunologi/immunkemi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Rahman, Arman
    Qadri, Firdausi
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Shirin, Tahmina
    Hammarström, Marie-Louise
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Immunologi/immunkemi.
    Induction of immunomodulatory miR-146a and miR-155 in small intestinal epithelium of Vibrio cholerae infected patients at acute stage of cholera2017Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, nr 3, artikel-id 0173817Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The potential immunomodulatory role of microRNAs in small intestine of patients with acute watery diarrhea caused by Vibrio cholerae O1 or enterotoxigenic Escherichia coli (ETEC) infection was investigated. Duodenal biopsies were obtained from study-participants at the acute (day 2) and convalescent (day 21) stages of disease, and from healthy individuals. Levels of miR-146a, miR-155 and miR-375 and target gene (IRAK1, TRAF6, CARD10) and 11 cytokine mRNAs were determined by qRT-PCR. The cellular source of microRNAs in biopsies was analyzed by in situ hybridization. The ability of V. cholerae bacteria and their secreted products to cause changes in microRNA- and mRNA levels in polarized tight monolayers of intestinal epithelial cells was investigated. miR-146a and miR-155 were expressed at significantly elevated levels at acute stage of V. cholerae infection and declined to normal at convalescent stage (P<0.009 versus controls; P = 0.03 versus convalescent stage, pairwise). Both microRNAs were mainly expressed in the epithelium. Only marginal down-regulation of target genes IRAK1 and CARD10 was seen and a weak cytokine-profile was identified in the acute infected mucosa. No elevation of microRNA levels was seen in ETEC infection. Challenge of tight monolayers with the wild type V. cholerae O1 strain C6706 and clinical isolates from two study-participants, caused significant increase in miR-155 and miR-146a by the strain C6706 (P<0.01). One clinical isolate caused reduction in IRAK1 levels (P<0.05) and none of the strains induced inflammatory cytokines. In contrast, secreted factors from these strains caused markedly increased levels of IL-8, IL-1β, and CARD10 (P<0.001), without inducing microRNA expression. Thus, miR-146a and miR-155 are expressed in the duodenal epithelium at the acute stage of cholera. The inducer is probably the V. cholerae bacterium. By inducing microRNAs the bacterium can limit the innate immune response of the host, including inflammation evoked by its own secreted factors, thereby decreasing the risk of being eliminated.

  • 60. Bjarnsholt, Thomas
    et al.
    Hoiby, Niels
    Donelli, Gianfranco
    Imbert, Christine
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Understanding biofilms: are we there yet?2012Ingår i: FEMS Immunology and Medical Microbiology, ISSN 0928-8244, E-ISSN 1574-695X, Vol. 65, nr 2, s. 125-126Artikel i tidskrift (Övrigt vetenskapligt)
  • 61.
    Björk, Glenn R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Adventures with Frameshift Supressor tRNAs2011Ingår i: Lure of Bacterial Genetics: a Tribute to John Roth / [ed] Stanley Maloy, Kelly T. Hughes and Josep Casadesús, WASHINGTON: American society for microbiology, ASM Press , 2011, s. 131-140Kapitel i bok, del av antologi (Refereegranskat)
  • 62.
    Brady, L. Jeannine
    et al.
    Department of Oral Biology, University of Florida, Gainesville, FL 32610, USA.
    Maddocks, Sarah E.
    School of Oral and Dental Sciences, University of Bristol, Bristol BS1 2LY, UK.
    Larson, Matthew R.
    Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
    Forsgren, Nina
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    Persson, Karina
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Deivanayagam, Champion C.
    Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
    Jenkinson, Howard F.
    School of Oral and Dental Sciences, University of Bristol, Bristol BS1 2LY, UK.
    The changing faces of Streptococcus antigen I/II polypeptide family adhesins2010Ingår i: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 77, nr 2, s. 276-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Streptococcus mutans antigen I/II (AgI/II) protein was one of the first cell wall-anchored adhesins identified in Gram-positive bacteria. It mediates attachment of S. mutans to tooth surfaces and has been a focus for immunization studies against dental caries. The AgI/II family polypeptides recognize salivary glycoproteins, and are also involved in biofilm formation, platelet aggregation, tissue invasion and immune modulation. The genes encoding AgI/II family polypeptides are found among Streptococcus species indigenous to the human mouth, as well as in Streptococcus pyogenes, S. agalactiae and S. suis. Evidence of functionalities for different regions of the AgI/II proteins has emerged. A sequence motif within the C-terminal portion of Streptococcus gordonii SspB (AgI/II) is bound by Porphyromonas gingivalis, thus promoting oral colonization by this anaerobic pathogen. The significance of other epitopes is now clearer following resolution of regional crystal structures. A new picture emerges of the central V (variable) region, predicted to contain a carbohydrate-binding trench, being projected from the cell surface by a stalk formed by an unusual association between an N-terminal α-helix and a C-terminal polyproline helix. This presentation mode might be important in determining functional conformations of other Gram-positive surface proteins that have adhesin domains flanked by α-helical and proline-rich regions.

    Ever since dental caries (tooth decay) was first shown to be caused by bacteria, there has been continued interest in developing vaccine or passive immunization protocols for its control or prevention (Lehner et al., 1980). Although dental caries is not fatal, and in developed countries caries is now considered to be largely avoidable through controlled diet and good oral hygiene, there remain significant problems with childhood disease, especially among indigent populations. Consequently, caries is one of the most common worldwide infectious diseases. Therefore, research continues towards employing vaccine formulations comprised of peptide components derived from surface proteins of Streptococcus mutans, a major agent associated with dental caries (Lehner et al., 1975). One of the most promising strategies seems to be delivery of peptides, derived from glucan-binding protein B (GbpB) and antigen I/II (AgI/II) protein, via a mucosal (nasal) route. The GbpB polypeptide binds extracellular glucans, thus promoting co-adhesion of S. mutans cells in the development of dental plaque (Taubman and Nash, 2006). The AgI/II protein (also named P1, SpaP, AgB or PAc) is a major surface protein that functions as an adhesin, attaching S. mutans to the saliva-coated tooth enamel surface (Koga et al., 1990; Kelly et al., 1995). Antibodies against SpaP and GbpB block adherence and co-adhesion, respectively, thus disrupting colonization of the oral cavity by S. mutans (Ma et al., 1990; 1998; Taubman and Nash, 2006).

    The terminology AgI/II derives from the identification of two major cell wall antigens I and II in S. mutans by Russell et al. (1980), and the subsequent recognition that AgII was a component of AgI. Following the discovery of AgI/II, it became apparent that genes encoding orthologous proteins were widely dispersed among the streptococci (Jenkinson and Demuth, 1997). The viridans Streptococcus AgI/II adhesins range in composition from 1310 to 1653 amino acid (aa) residues, while the Streptococcus agalactiae AgI/II proteins are smaller (826–932 aa residues) (Tettelin et al., 2005). The widespread distribution of these AgI/II protein genes across the streptococci is perhaps not surprising, given the complex streptococcal communities that exist on surfaces of the oro- and naso-pharynx and within the bacterial soup of saliva. It is interesting, though, that the AgI/II family polypeptide genes have not yet been discovered in Streptococcus pneumoniae, which might be by the fact that S. pneumoniae forms a distinct evolutionary cluster (Kilian et al., 2008).

  • 63.
    Brage, Monica
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Holmlund, A
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Humoral immune response to Aggregatibacter actinomycetemcomitans leukotoxin2011Ingår i: Journal of Periodontal Research, ISSN 0022-3484, E-ISSN 1600-0765, Vol. 46, nr 2, s. 170-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background and Objective: Periodontal disease is an inflammatory condition caused by bacterial infections that result in loss of the tooth supporting tissue. The periodontal pathogens produce virulence factors with capacity to affect the host immune response. Aggregatibacter actinomycetemcomitans is a periodontal pathogen that produces a leukotoxin that specifically affects human leukocytes. The aims of the present study were to examine the presence and function of systemic antibodies to the leukotoxin. Material and Methods:  One hundred and ninety-seven middle-aged (57 ± 5 years) Swedes with well-documented periodontal status and medical factors related to cardiovascular diseases were studied. These data have been published previously. The serum samples were examined for the presence of leukotoxin antibodies by western blot and the capacity to neutralize leukotoxicity in an activity assay with leukotoxin and cultured leukemic cells. Results:  The results showed a high prevalence (57%) of antibodies against A. actinomycetemcomitans leukotoxin in the analyzed population. These antibodies were correlated with leukotoxin neutralizing capacity as well as with the ELISA titers of A. actinomycetemcomitans-specific IgA and IgG. In addition, high levels of leukotoxin antibodies were correlated with increasing age, but not with periodontal disease parameters or cardiovascular risk factors. Conclusion:  Systemic antibodies against A. actionmycetemcomitans leukotoxin were common in this adult Swedish population. These antibodies might contribute to limit the systemic effects of the infection.

  • 64. Brazier, J
    et al.
    Chmelar, D
    Dubreuil, L
    Feierl, G
    Hedberg, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Kalenic, S
    Könönen, E
    Lundgren, B
    Malamou-Ladas, H
    Nagy, E
    Sullivan, Å
    Nord, CE
    European surveillance study on antimicrobial susceptibility of Gram-positive anaerobic cocci2008Ingår i: International Journal of Antimicrobial Agents, ISSN 0924-8579, E-ISSN 1872-7913, Vol. 31, nr 4, s. 316-320Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gram-positive anaerobic cocci (GPAC) are a heterogeneous group of microorganisms frequently isolated from local and systemic infections. In this study, the antimicrobial susceptibilities of clinical strains isolated in 10 European countries were investigated. After identification of 299 GPAC to species level, the minimum inhibitory concentrations of penicillin, imipenem, clindamycin, metronidazole, vancomycin and linezolid were determined by the agar dilution method according to the Clinical and Laboratory Standards Institute. The majority of isolates were identified as Finegoldia magna and Parvimonas micra (formerly Peptostreptococcus micros), isolated from skin and soft tissue infections. All isolates were susceptible to imipenem, metronidazole, vancomycin and linezolid. Twenty-one isolates (7%) were resistant to penicillin (n=13) and/or to clindamycin (n=12). Four isolates were resistant to both agents. The majority of resistant isolates were identified as F. magna and originated from blood, abscesses and soft tissue infections.

  • 65. Browall, Sarah
    et al.
    Norman, Martin
    Tångrot, Jeanette
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Bioinformatics Infrastructure for Life Sciences, Computational Life Science Cluster.
    Galanis, Ilias
    Sjöstrom, Karin
    Dagerhamn, Jessica
    Hellberg, Christel
    Pathak, Anuj
    Spadafina, Tiziana
    Sandgren, Andreas
    Bättig, Patrick
    Franzén, Oscar
    Andersson, Björn
    Örtqvist, Åke
    Normark, Staffan
    Henriques-Normark, Birgitta
    Intraclonal Variations Among Streptococcus pneumoniae Isolates Influence the Likelihood of Invasive Disease in Children2014Ingår i: Journal of Infectious Diseases, ISSN 0022-1899, E-ISSN 1537-6613, Vol. 209, nr 3, s. 377-388Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background. Pneumococcal serotypes are represented by a varying number of clonal lineages with different genetic contents, potentially affecting invasiveness. However, genetic variation within the same genetic lineage may be larger than anticipated. Methods. A total of 715 invasive and carriage isolates from children in the same region and during the same period were compared using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. Bacterial genome sequencing, functional assays, and in vivo virulence mice studies were performed. Results. Clonal types of the same serotype but also intraclonal variants within clonal complexes (CCs) showed differences in invasive-disease potential. CC138, a common CC, was divided into several PFGE patterns, partly explained by number, location, and type of temperate bacteriophages. Whole-genome sequencing of 4 CC138 isolates representing PFGE clones with different invasive-disease potentials revealed intraclonal sequence variations of the virulence-associated proteins pneumococcal surface protein A (PspA) and pneumococcal choline-binding protein C (PspC). A carrier isolate lacking PcpA exhibited decreased virulence in mice, and there was a differential binding of human factor H, depending on invasiveness. Conclusions. Pneumococcal clonal types but also intraclonal variants exhibited different invasive-disease potentials in children. Intraclonal variants, reflecting different prophage contents, showed differences in major surface antigens. This suggests ongoing immune selection, such as that due to PspC-mediated complement resistance through varied human factor H binding, that may affect invasiveness in children.

  • 66. Bruening, Janina
    et al.
    Lasswitz, Lisa
    Banse, Pia
    Kahl, Sina
    Marinach, Carine
    Vondran, Florian W.
    Kaderali, Lars
    Silvie, Olivier
    Pietschmann, Thomas
    Meissner, Felix
    Gerold, Gisa
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi. Umeå universitet, Medicinska fakulteten, Wallenberg centrum för molekylär medicin vid Umeå universitet (WCMM). Insitute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany.
    Hepatitis C virus enters liver cells using the CD81 receptor complex proteins calpain-5 and CBLB2018Ingår i: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 14, nr 7, artikel-id e1007111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hepatitis C virus (HCV) and the malaria parasite Plasmodium use the membrane protein CD81 to invade human liver cells. Here we mapped 33 host protein interactions of CD81 in primary human liver and hepatoma cells using high-resolution quantitative proteomics. In the CD81 protein network, we identified five proteins which are HCV entry factors or facilitators including epidermal growth factor receptor (EGFR). Notably, we discovered calpain-5 (CAPN5) and the ubiquitin ligase Casitas B-lineage lymphoma proto-oncogene B (CBLB) to form a complex with CD81 and support HCV entry. CAPN5 and CBLB were required for a post-binding and pre-replication step in the HCV life cycle. Knockout of CAPN5 and CBLB reduced susceptibility to all tested HCV genotypes, but not to other enveloped viruses such as vesicular stomatitis virus and human coronavirus. Furthermore, Plasmodium sporozoites relied on a distinct set of CD81 interaction partners for liver cell entry. Our findings reveal a comprehensive CD81 network in human liver cells and show that HCV and Plasmodium highjack selective CD81 interactions, including CAPN5 and CBLB for HCV, to invade cells.

  • 67.
    Brundin, Malin
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Figdor, David
    Department of Microbiology, Monash University, Melbourne, Australia.
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Sjögren, Ulf
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Preservation of bacterial dna by human dentin2014Ingår i: Journal of Endodontics, ISSN 0099-2399, E-ISSN 1878-3554, Vol. 40, nr 2, s. 241-245Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    INTRODUCTION: The capacity of dentin and collagen to bind DNA and protect against spontaneous and nuclease-induced degradation was evaluated individually and by the incubation of DNA with nuclease-producing bacteria in a mixed culture.

    METHODS: Extracted Fusobacterium nucleatum DNA was incubated with dentin shavings or collagen for 90 minutes. The DNA-bound substrates were incubated in different media (water, sera, and DNase I) for up to 3 months. Amplifiable DNA was released from dentin using EDTA,or from collagen using proteinase K, and evaluated by polymerase chain reaction (PCR). The stability of dentin-bound DNA was also assessed in a mixed culture (Parvimonas micra and Pseudoramibacter alactolyticus) containing a DNase-producing species, Prevotella intermedia. Samples were analyzed for amplifiable DNA.

    RESULTS: In water, dentin-bound DNA was recoverable by PCR at 3 months compared with no detectable DNA after 4 weeks in controls (no dentin). DNA bound to collagen was detectable by PCR after 3 months of incubation in water. In 10% human sera, amplifiable DNA was detectable at 3 months when dentin bound and in controls (no dentin). In mixed bacterial culture, dentin-bound DNA was recoverable throughout the experimental period (3 months), compared with no recoverable F. nucleatum DNA within 24 hours in controls (no dentin).

    CONCLUSIONS: There is a strong binding affinity between DNA and dentin, and between DNA and serum proteins or collagen. These substrates preserve DNA against natural decomposition and protect DNA from nuclease activity, factors that may confound molecular analysis of the endodontic microbiota yet favor paleomicrobiological studies of ancient DNA.

  • 68.
    Bröms, Jeanette E
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi.
    Francis, Matthew S
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Forsberg, Ake
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Diminished LcrV secretion attenuates Yersinia pseudotuberculosis virulence.2007Ingår i: J Bacteriol, ISSN 0021-9193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many Gram negative bacterial pathogenicity factors that function beyond the outer membrane are secreted via a contact-dependent type III secretion system. Two types of substrates are predestined for this mode of secretion; anti-host effectors that are translocated directly into target cells and the translocators required for targeting of the effectors across the host cell membrane. N-terminal secretion signals are important for recognition of the protein cargo by the type III secretion machinery. Even though such signals are known for several effectors, a consensus signal sequence is not obvious. One of the tranclocators, LcrV, has been attributed other functions in addition to its role in translocation. These functions include regulation, presumably via interaction with LcrG inside the bacteria and immunomodulation via interaction with TLR2. Here we wanted to address the significance of the specific targeting of LcrV to the exterior for its function in regulation, effector targeting and virulence. The results, highlighting key N-terminal amino acids important for LcrV secretion, allowed us to dissect the role of LcrV in regulation from that in effector targeting/virulence. While only low levels of exported LcrV were required for in vitro effector translocation as deduced by a cell infection assay, fully functional export of LcrV was found to be a prerequisite for its role in virulence in the systemic murine infection model.

  • 69.
    Bröms, Jeanette E.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Ishikawa, Takahiko
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Wai, Sun N.
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    A functional VipA-VipB interaction is required for the type VI secretion system activity of Vibrio cholerae O1 strain A15522013Ingår i: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 13, s. 96-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Many Gram-negative bacteria rely on a type VI secretion system (T6SS) to infect eukaryotic cells or to compete against other microbes. Common to these systems is the presence of two conserved proteins, in Vibrio cholerae denoted VipA and VipB, which have been shown to interact in many clinically relevant pathogens. In this study, mutagenesis of a defined region within the VipA protein was used to identify residues important for VipB binding in V. cholerae O1 strain A1552. Results: A dramatically diminished interaction was shown to correlate with a decrease in VipB stability and a loss of hemolysin co-regulated protein (Hcp) secretion and rendered the bacterium unable to compete with Escherichia coli in a competition assay. Conclusions: This confirms the biological relevance of the VipA-VipB interaction, which is essential for the T6SS activity of many important human pathogens.

  • 70.
    Bröms, Jeanette E
    et al.
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Lavander, Moa
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Dissection of the Functions of the IglC Protein of Francisella tularensis2010Ingår i: The challenge of highly pathogenic microorganisms: mechanisms of virulence and novel medical countermeasures, Springer, 2010, s. 67-75Konferensbidrag (Refereegranskat)
    Abstract [en]

    Francisella tularensis harbors genes with similarity to genes encoding components of a type VI secretion system (T6SS). These include iglA and iglB, the homologues of which are conserved in T6SSs. They are part of the igl operon, also encompassing the iglC and iglD genes. We have used a yeast two-hybrid system to study the interaction of the Igl proteins of E tularensis LVS. Previously, we identified a region of IglA necessary for efficient binding to IglB as well as for IglAB protein stability and intra-macrophage growth with an essential role for a conserved alpha-helical region. Thus, IglA-IglB complex formation is clearly crucial for Francisella pathogenicity and the same interaction is conserved in other human pathogens. Herein, the interaction of IglC with other members of the operon was investigated. It showed no binding to the other members in the yeast two-hybrid assay and we found also that two cysteine residues, C191 and C192, predicted to be putative prenylation sites, played no role for the important contribution of IglC to the intracellular replication of E tularensis although C191 was important for the stability of the protein.

  • 71.
    Bröms, Jeanette E.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Meyer, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Lavander, Moa
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Larsson, Pär
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    DotU and VgrG, core components of type VI secretion systems, are essential for Francisella LVS pathogenicity2012Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, nr 4, artikel-id e34639Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Gram-negative bacterium Francisella tularensis causes tularemia, a disease which requires bacterial escape from phagosomes of infected macrophages. Once in the cytosol, the bacterium rapidly multiplies, inhibits activation of the inflammasome and ultimately causes death of the host cell. Of importance for these processes is a 33-kb gene cluster, the Francisella pathogenicity island (FPI), which is believed to encode a type VI secretion system (T6SS). In this study, we analyzed the role of the FPI-encoded proteins VgrG and DotU, which are conserved components of type VI secretion (T6S) clusters. We demonstrate that in F. tularensis LVS, VgrG was shown to form multimers, consistent with its suggested role as a trimeric membrane puncturing device in T6SSs, while the inner membrane protein DotU was shown to stabilize PdpB/IcmF, another T6SS core component. Upon infection of J774 cells, both Delta vgrG and Delta dotU mutants did not escape from phagosomes, and subsequently, did not multiply or cause cytopathogenicity. They also showed impaired activation of the inflammasome and marked attenuation in the mouse model. Moreover, all of the DotU-dependent functions investigated here required the presence of three residues that are essentially conserved among all DotU homologues. Thus, in agreement with a core function in T6S clusters, VgrG and DotU play key roles for modulation of the intracellular host response as well as for the virulence of F. tularensis.

  • 72.
    Bröms, Jeanette E.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Meyer, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Department of Experimental Medical Science, Section for Immunology, Lund University, Lund, Sweden.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    A mutagenesis-based approach identifies amino acids in the N-terminal part of Francisella tularensis IglE that critically control type VI system-mediated secretion2017Ingår i: Virulence, ISSN 2150-5594, E-ISSN 2150-5608, Vol. 8, nr 6, s. 821-847Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Gram-negative bacterium Francisella tularensis is the etiological agent of the zoonotic disease tularemia. Its life cycle is characterized by an ability to survive within phagocytic cells through phagosomal escape and replication in the cytosol, ultimately causing inflammasome activation and host cell death. Required for these processes is the Francisella Pathogenicity Island (FPI), which encodes a Type VI secretion system (T6SS) that is active during intracellular infection. In this study, we analyzed the role of the FPI-component IglE, a lipoprotein which we previously have shown to be secreted in a T6SS-dependent manner. We demonstrate that in F. tularensis LVS, IglE is an outer membrane protein. Upon infection of J774 cells, an Delta iglE mutant failed to escape from phagosomes, and subsequently, to multiply and cause cytopathogenicity. Moreover, Delta iglE was unable to activate the inflammasome, to inhibit LPS-stimulated secretion of TNF-alpha, and showed marked attenuation in the mouse model. In F. novicida, IglE was required for in vitro secretion of IglC and VgrG. A mutagenesis-based approach involving frameshift mutations and alanine substitution mutations within the first similar to 38 residues of IglE revealed that drastic changes in the sequence of the extreme N-terminus (residues 2-6) were well tolerated and, intriguingly, caused hyper-secretion of IglE during intracellular infection, while even subtle mutations further downstream lead to impaired protein function. Taken together, this study highlights the importance of IglE in F. tularensis pathogenicity, and the contribution of the N-terminus for all of the above mentioned processes.

  • 73.
    Bröms, Jeanette E.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Meyer, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Sun, Kun
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Lavander, Moa
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Unique substrates secreted by the type VI secretion system of Francisella tularensis during intramacrophage infection2012Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, nr 11, artikel-id e50473Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gram-negative bacteria have evolved sophisticated secretion machineries specialized for the secretion of macromolecules important for their life cycles. The Type VI secretion system (T6SS) is the most widely spread bacterial secretion machinery and is encoded by large, variable gene clusters, often found to be essential for virulence. The latter is true for the atypical T6SS encoded by the Francisella pathogenicity island (FPI) of the highly pathogenic, intracellular bacterium Francisella tularensis. We here undertook a comprehensive analysis of the intramacrophage secretion of the 17 FPI proteins of the live vaccine strain, LVS, of F. tularensis. All were expressed as fusions to the TEM beta-lactamase and cleavage of the fluorescent substrate CCF2-AM, a direct consequence of the delivery of the proteins into the macrophage cytosol, was followed over time. The FPI proteins IglE, IglC, VgrG, IglI, PdpE, PdpA, IglJ and IglF were all secreted, which was dependent on the core components DotU, VgrG, and IglC, as well as IglG. In contrast, the method was not directly applicable on F. novicida U112, since it showed very intense native beta-lactamase secretion due to FTN_1072. Its role was proven by ectopic expression in trans in LVS. We did not observe secretion of any of the LVS substrates VgrG, IglJ, IglF or IglI, when tested in a FTN_1072 deficient strain of F. novicida, whereas IglE, IglC, PdpA and even more so PdpE were all secreted. This suggests that there may be fundamental differences in the T6S mechanism among the Francisella subspecies. The findings further corroborate the unusual nature of the T6SS of F. tularensis since almost all of the identified substrates are unique to the species.

  • 74.
    Bröms, Jeanette E
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Lavander, Moa
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    The role of the Francisella Tularensis pathogenicity island in type VI secretion, intracellular survival, and modulation of host cell signaling2010Ingår i: Frontiers in microbiology, ISSN 1664-302X, Vol. 1, s. 136-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis is a highly virulent gram-negative intracellular bacterium that causes the zoonotic disease tularemia. Essential for its virulence is the ability to multiply within host cells, in particular monocytic cells. The bacterium has developed intricate means to subvert host immune mechanisms and thereby facilitate its intracellular survival by preventing phagolysosomal fusion followed by escape into the cytosol, where it multiplies. Moreover, it targets and manipulates numerous host cell signaling pathways, thereby ameliorating the otherwise bactericidal capacity. Many of the underlying molecular mechanisms still remain unknown but key elements, directly or indirectly responsible for many of the aforementioned mechanisms, rely on the expression of proteins encoded by the Francisella pathogenicity island (FPI), suggested to constitute a type VI secretion system. We here describe the current knowledge regarding the components of the FPI and the roles that have been ascribed to them.

  • 75.
    Bröms, Jeanette
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Forslund, Anna-Lena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Forsberg, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Francis, Matthew
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Dissection of homologous translocon operons reveals a distinct role for YopD in type III secretion by Yersinia pseudotuberculosis2003Ingår i: Microbiology, ISSN 1350-0872, E-ISSN 1465-2080, Vol. 149, nr 9, s. 2615-2626Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The homologous pcrGVHpopBD and lcrGVHyopBD translocase operons of Pseudomonas aeruginosa and pathogenic Yersinia spp., respectively, are responsible for the translocation of anti-host effectors into the cytosol of infected eukaryotic cells. In Yersinia, this operon is also required for yop-regulatory control. To probe for key molecular interactions during the infection process, the functional interchangeability of popB/yopB and popD/yopD was investigated. Secretion of PopB produced in trans in a yopB null mutant of Yersinia was only observed when co-produced with its native chaperone PcrH, but this was sufficient to complement the yopB translocation defect. The Yersinia yopD null mutant synthesized and secreted PopD even in the absence of native PcrH, yet this did not restore YopD-dependent yop-regulatory control or effector translocation. Thus, this suggests that key residues in YopD, which are not conserved in PopD, are essential for functional Yersinia type III secretion.

  • 76.
    Bueno, Emilio
    et al.
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). CSIC, Estac Expt Zaidin, Dept Soil Microbiol & Symbiot Syst, C Profesor Albareda 1, E-18008 Granada, Spain.
    Robles, Eloy F.
    Torres, Maria J.
    Krell, Tino
    Bedmar, Eulogio J.
    Delgado, Maria J.
    Mesa, Socorro
    Disparate response to microoxia and nitrogen oxides of the Bradyrhizobium japonicum napEDABC, nirK and norCBQD denitrification genes2017Ingår i: Nitric oxide, ISSN 1089-8603, E-ISSN 1089-8611, Vol. 68, s. 137-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Expression of the Bradyrhizobium japonicum napEDABC, nirK and norCBQD denitrification genes requires low oxygen (O-2) tension and nitrate (NO3), through a regulatory network comprised of two coordinated cascades, FixLJ-FixK(2)-NnrR and RegSR-NifA. To precisely understand how these signals are integrated in the FixLJ-FixK(2)-NnrR circuit, we analyzed beta-Galactosidase activities from napE-lacZ, nirK-lacZ and norC-lacZ fusions, and performed analyses of NapC and NorC levels as well as periplasmic nitrate reductase (Nap) activity, in B. japonicum wildtype and fixK(2) and nnrR mutant backgrounds. While microoxic conditions (2% O-2 at headspace) were sufficient to induce expression of napEDABC and nirK genes and this control depends on FixK(2), norCBQD expression requires, in addition to microoxia, nitric oxide gas (NO) and both FixK(2) and NnrR transcription factors. Purified FixK(2) protein directly interacted and activated transcription in collaboration with B. japonicum RNA polymerase (RNAP) from the napEDABC and nirK promoters, but not from the norCBQD promoter. Further, recombinant NnrR protein bound exclusively to the norCBQD promoter in an O-2-sensitive manner. Our work suggest a disparate regulation of B. japonicum denitrifying genes expression with regard to their dependency to microoxia, nitrogen oxides (NOx), and the regulatory proteins FixK(2) and NnrR. In this control, expression of napEDABC and nirK genes requires microoxic conditions and directly depends on FixK2, while expression of norCBQD genes relies on NO, being NnrR the candidate which directly interacts with the norCBQD promoter. 

  • 77.
    Bueno, Emilio
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Sit, Brandon
    Waldor, Matthew K.
    Cava, Felipe
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Anaerobic nitrate reduction divergently governs population expansion of the enteropathogen Vibrio cholerae2018Ingår i: Nature Microbiology, E-ISSN 2058-5276, Vol. 3, nr 12, s. 1346-1353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To survive and proliferate in the absence of oxygen, many enteric pathogens can undergo anaerobic respiration within the host by using nitrate (NO3-) as an electron acceptor(1,2). In these bacteria, NO3- is typically reduced by a nitrate reductase to nitrite (NO2-), a toxic intermediate that is further reduced by a nitrite reductase(3). However, Vibrio cholerae, the intestinal pathogen that causes cholera, lacks a nitrite reductase, leading to NO2- accumulation during nitrate reduction 4(.) Thus, V. cholerae is thought to be unable to undergo NO3-(-)dependent anaerobic respiration(4). Here, we show that during hypoxic growth, NO3- reduction in V. cholerae divergently affects bacterial fitness in a manner dependent on environmental pH. Remarkably, in alkaline conditions, V. cholerae can reduce NO3- to support population growth. Conversely, in acidic conditions, accumulation of NO2- from NO3- reduction simultaneously limits population expansion and preserves cell viability by lowering fermentative acid production. Interestingly, other bacterial species such as Salmonella typhimurium, enterohaemorrhagic Escherichia coli (EHEC) and Citrobacter rodentium also reproduced this pH-dependent response, suggesting that this mechanism might be conserved within enteric pathogens. Our findings explain how a bacterial pathogen can use a single redox reaction to divergently regulate population expansion depending on the fluctuating environmental pH.

  • 78.
    Bugaytsova, Jeanna A.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Swedish Defence Research Agency, 906 21 Umeå, Sweden.
    Chernov, Yevgen A.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gideonsson, Pär
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Henriksson, Sara
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mendez, Melissa
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Sjöström, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mahdavi, Jafar
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. School of Life Sciences, CBS, University of Nottingham, NG7 2RD Nottingham, UK.
    Shevtsova, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Ilver, Dag
    Moonens, Kristof
    Quintana-Hayashi, Macarena P.
    Moskalenko, Roman
    Aisenbrey, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Bylund, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Schmidt, Alexej
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Åberg, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Brännström, Kristoffer
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Koeniger, Verena
    Vikström, Susanne
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Rakhimova, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Hofer, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Ögren, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Avdelningen för medicin.
    Liu, Hui
    Goldman, Matthew D.
    Whitmire, Jeannette M.
    Åden, Jörgen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Younson, Justine
    Kelly, Charles G.
    Gilman, Robert H.
    Chowdhury, Abhijit
    Mukhopadhyay, Asish K.
    Nair, G. Balakrish
    Papadakos, Konstantinos S.
    Martinez-Gonzalez, Beatriz
    Sgouras, Dionyssios N.
    Engstrand, Lars
    Unemo, Magnus
    Danielsson, Dan
    Suerbaum, Sebastian
    Oscarson, Stefan
    Morozova-Roche, Ludmilla A.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Olofsson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gröbner, Gerhard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Holgersson, Jan
    Esberg, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Strömberg, Nicklas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Landström, Maréne
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Eldridge, Angela M.
    Chromy, Brett A.
    Hansen, Lori M.
    Solnick, Jay V.
    Linden, Sara K.
    Haas, Rainer
    Dubois, Andre
    Merrell, D. Scott
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Remaut, Han
    Arnqvist, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Berg, Douglas E.
    Boren, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Helicobacter pylori Adapts to Chronic Infection and Gastric Disease via pH-Responsive BabA-Mediated Adherence2017Ingår i: Cell Host and Microbe, ISSN 1931-3128, E-ISSN 1934-6069, Vol. 21, nr 3, s. 376-389Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The BabA adhesin mediates high-affinity binding of Helicobacter pylori to the ABO blood group antigen-glycosylated gastric mucosa. Here we show that BabA is acid responsive-binding is reduced at low pH and restored by acid neutralization. Acid responsiveness differs among strains; often correlates with different intragastric regions and evolves during chronic infection and disease progression; and depends on pH sensor sequences in BabA and on pH reversible formation of high-affinity binding BabA multimers. We propose that BabA's extraordinary reversible acid responsiveness enables tight mucosal bacterial adherence while also allowing an effective escape from epithelial cells and mucus that are shed into the acidic bactericidal lumen and that bio-selection and changes in BabA binding properties through mutation and recombination with babA-related genes are selected by differences among individuals and by changes in gastric acidity over time. These processes generate diverse H. pylori subpopulations, in which BabA's adaptive evolution contributes to H. pylori persistence and overt gastric disease.

  • 79.
    Bugaytsova, Jeanna
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Björnhamn, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Henriksson, Sara
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Johansson, Pär
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mendez, Melissa
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Sjöström, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Brännström, Kristoffer
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Aisenbrey, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shevtsova, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Bylund, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mahdavi, Jafar
    Ögren, Johan
    Ilver, Dag
    Gilman, Robert H
    Chowdhury, Abhijit
    The Swedish Institute for Control, Solna, Swede.
    Mukhopadhyay, Asish K
    Engstrand, Lars
    Oscarson, Stefan
    Kelly, Charles G
    Younson, Justine S
    Odenbreit, Stefan
    Solnick, Jay
    Gröbner, Gerhard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Haas, Rainer
    Dubois, Andre
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Berg, Douglas E
    Arnqvist, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Borén, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    pH regulated H. pylori adherence: implications for persistent infection and diseaseManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Helicobacter pylori’s BabA adhesin binds strongly to gastric mucosal ABH/Leb glycans on the stomach epithelium and overlying mucus, materials continuously shed into the acidic gastric lumen. Here we report that this binding is acid labile, acid inactivation is fully reversible; and acid lability profiles vary with BabA sequence and correlate with disease patterns. Isogenic H. pylori strains from the gastric antrum and more acidic corpus were identified that differed in acid lability of receptor binding and in sequence near BabA’s carbohydrate binding domain. We propose that reversible acid inactivation of receptor binding helps H. pylori avoid clearance by mucosal shedding, and that strain differences in acid lability affect tissue tropism and the spectrum of associated gastric diseases.

  • 80.
    Bugaytsova, Jeanna
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Chernov, Yevgen A
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gideonsson, Pär
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Mendez, Melissa
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Henriksson, Sara
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Mahdavi, Jafar
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. School of Life Sciences, CBS, University of Nottingham, Nottingham, UK..
    Quintana-Hayashi, Macarena
    Department of Biochemistry and Cell biology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden..
    Shevtsova, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Sjöström, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Moskalenko, Roman
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Department of Pathology, Medical Institute, State University, Sumy, Ukraine.
    Aisenbrey, Christopher
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Université de Strasbourg, Institut de Chimie, Strasbourg, France.
    Moonens, Kristof
    Structural and Molecular Microbiology, VIB Department of Structural Biology, Belgium.
    Björnham, Oscar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. FOI Totalförsvarets Forskningsinstitut, Umeå, Sweden..
    Brännström, Kristoffer
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Bylund, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Königer, Verena
    Max von Pettenkofer Institute of Hygiene and Medical Microbiology, LMU, Munich, Germany.
    Vikström, Susanne
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Schmidt, Alexej
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap.
    Rakhimova, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Hofer, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Ögren, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Ilver, Dag
    Department of Biochemistry and Cell biology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Liu, Hui
    Department of Medicine, USUHS, Bethesda, MD, USA.
    Goldman, Matthew
    Department of Pediatrics, USUHS, Bethesda, MD, USA.
    Whitmire, Jeannette M
    Department of Microbiology and Immunology, USUHS, Bethesda, MD USA.
    Kelly, Charles G
    King's College London, Dental Institute, London, UK.
    Gilman, Robert H
    Department of International Health, John Hopkins School of Public Health, Baltimore, MD, USA.
    Chowdhury, Abhijit
    Centre for Liver Research, School of Digestive and Liver Diseases, Institute of Post Graduate Medical Education & Research, Kolkata, India.
    Mukhopadhyay, Asish K
    Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, India.
    Nair, Balakrish G
    Translational Health Science and Technology Institute, Haryana, India.
    Papadakos, Konstantinos S
    Hellenic Pasteur Institute, Athens, Greece.
    Martinez-Gonzalez, Beatriz
    Hellenic Pasteur Institute, Athens, Greece.
    Sgouras, Dionyssios N
    Hellenic Pasteur Institute, Athens, Greece.
    Engstrand, Lars
    Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
    Unemo, Magnus
    Department of Laboratory Medicine, Microbiology, Örebro University Hospital, Örebro, Sweden.
    Danielsson, Dan
    Department of Laboratory Medicine, Microbiology, Örebro University Hospital, Örebro, Sweden.
    Sebastian, Suerbaum
    Institute for Medical Microbiology and Hospital Epidemiology Hannover Medical School, Hannover, Germany.
    Oscarson, Stefan
    Centre for Synthesis and Chemical Biology, School of Chemistry, University College Dublin, Dublin, Ireland.
    Morozova-Roche, Ludmilla
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Gröbner, Gerhard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Holgersson, Jan
    Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden.
    Strömberg, Nicklas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Esberg, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Eldridge, Angela
    Department of Pathology and Laboratory Medicine, University of California Davis School of Medicine, Sacramento, CA, USA.
    Chromy, Brett A
    Department of Pathology and Laboratory Medicine, University of California Davis School of Medicine, Sacramento, CA, USA.
    Hansen, Lori
    Departments of Medical Microbiology and Immunology, Center for Comparative Medicine, University of California Davis, Davis, CA, USA.
    Solnick, Jay
    Departments of Medical Microbiology and Immunology, Center for Comparative Medicine, University of California Davis, Davis, CA, USA.
    Haas, Rainer
    Max von Pettenkofer Institute of Hygiene and Medical Microbiology, LMU Munich, Munich, Germany.
    Schedin, Staffan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Lindén, Sara K
    Department of Biochemistry and Cell biology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Dubois, Andre
    Department of Medicine, USUHS, Bethesda, MD, USA.
    Merrell, D. Scott
    Department of Microbiology and Immunology, USUHS, Bethesda, MD, USA.
    Remaut, Han
    Structural and Molecular Microbiology, VIB Department of Structural Biology, VIB, Brussels, Belgium.
    Arnqvist, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Berg, Douglas E
    Department of Medicine, University of California San Diego, La Jolla, CA, USA.
    Borén, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Acid Responsive Helicobacter pylori Adherence: Implications for Chronic Infection and DiseaseManuskript (preprint) (Övrigt vetenskapligt)
  • 81.
    Burman, Nils
    Umeå universitet, Medicinska fakulteten, Mikrobiologi.
    Antigenic variation in relapsing fever Borrelia1994Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The spirochete Borrelia hermsii avoids the immune response of its mammalian host through multiphasic antigenic variation. Serotype specificity is determined by Variable major proteins (Vmp), in the outer membrane. Through a non reciprocal recombination between linear plasmids, a formerly silent vmp gene replaces another vmp gene at a telomeric expression locus downstream from a common expression site. B. hermsii before and after the switch from serotype 7 to serotype 21, was examined in detail.

    The nucleotide sequence of the vmp7 and vmp21 genes and flanking regions was determined. The vmp7 and vmp21 are 77% identical in their coding sequence, and the deduced translation products are 63% identical. No antigenic cross reactivity is observed between Vmp7 and Vmp21. This suggests a folding of the proteins in which the similar regions are buried, and not exposed when it is presented at the bacterial surface. Vmp7 and Vmp21 have consensus sequences of prokaryotic lipoproteins and are processed as such when expressed in E. coli.

    The 5' regions of silent and expressed vmp7 and vmp21 were compared. Silent and active vmp7 and vmp21 genes shared a block of homologous sequence at their 5' ends. Sequences upstream of silent vmp7 and vmp21 genes lacked a promoter and differed substantially from each other. In this antigenic switch a vmp gene was activated by a recombination event which placed it downstream of a promoter.

    The vmp gene promoter is preceded by a poly(dT dA) ran and three imperfectlyrepeated elements of 2 kb. Each of the 2 kb repeats contains inverted repeats of approximately 0.2 kb at their termini. There is no evidence of the presence of similar elements elsewhere in the genome of B. hermsii. One or more of these elements may stimulate vmp gene switch or expression.

    The African relapsing fever species Borrelia crocidurae and the American species B. hermsii display many similarities. In both species the vmp genes are localised to linear plasmids, and the vmp genes are activated on the transcriptional level. The nucleotide sequence of their expression sites, however, are not related. Still, the possibility that the switch is mechanistically similar in B. crocidurae and B. hermsii, cannot be ruled out.

    The binding of B. crocidurae causes aggregation of erythrocytes around the spirochete. The aggregation is reminiscent of the erythrocyte rosetting seen in malarial infections. The erythrocytes at the B. crocidurae surface may protect them from clearance by the host. Thus, the rosetting may constitute an additional mechanism in B. crocidurae for the evasion of the immune reaction.

  • 82. Burmeister, Wim P
    et al.
    Guilligay, Delphine
    Cusack, Stephen
    Wadell, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi.
    Arnberg, Niklas
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi.
    Crystal structure of species D adenovirus fiber knobs and their sialic acid binding sites2004Ingår i: Journal of Virology, ISSN 0022-538X, E-ISSN 1098-5514, Vol. 78, nr 14, s. 7727-7736Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adenovirus serotype 37 (Ad37) belongs to species D and can cause epidemic keratoconjunctivitis, whereas the closely related Ad19p does not. Primary cell attachment by adenoviruses is mediated through receptor binding of the knob domain of the fiber protein. The knobs of Ad37 and Ad19p differ at only two positions, Lys240Glu and Asn340Asp. We report the high-resolution crystal structures of the Ad37 and Ad19p knobs, both native and in complex with sialic acid, which has been proposed as a receptor for Ad37. Overall, the Ad37 and Ad19p knobs are very similar to previously reported knob structures, especially to that of Ad5, which binds the coxsackievirus-adenovirus receptor (CAR). Ad37 and Ad19p knobs are structurally identical with the exception of the changed side chains and are structurally most similar to CAR-binding knobs (e.g., that of Ad5) rather than non-CAR-binding knobs (e.g., that of Ad3). The two mutations in Ad19p result in a partial loss of the exceptionally high positive surface charge of the Ad37 knob but do not affect sialic acid binding. This site is located on the top of the trimer and binds both alpha(2,3) and alpha(2,6)-linked sialyl-lactose, although only the sialic acid residue makes direct contact. Amino acid alignment suggests that the sialic acid binding site is conserved in several species D serotypes. Our results show that the altered viral tropism and cell binding of Ad19p relative to those of Ad37 are not explained by a different binding ability toward sialyl-lactose.

  • 83.
    Bylund, Göran O
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Nord, Stefan
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi.
    Lövgren, J Mattias
    Wikström, P Mikael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Alterations in the β flap and β' dock domains of the RNA polymerase abolish NusA-mediated feedback regulation of the metY-nusA-infB operon2011Ingår i: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 193, nr 16, s. 4113-4122Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The RimM protein in Escherichia coli is important for the in vivo maturation of 30S ribosomal subunits and a ΔrimM mutant grows poorly due to assembly and translational defects. These deficiencies are suppressed partially by mutations that increase the synthesis of another assembly protein, RbfA, encoded by the metY-nusA-infB operon. Among these suppressors are mutations in nusA that impair the NusA-mediated negative-feedback regulation at internal intrinsic transcriptional terminators of the metY-nusA-infB operon. We describe here the isolation of two new mutations, one in rpoB and one in rpoC (encoding the β and β' subunits of the RNA polymerase, respectively), that increase the synthesis of RbfA by preventing NusA from stimulating termination at the internal intrinsic transcriptional terminators of the metY-nusA-infB operon. The rpoB2063 mutation changed the isoleucine in position 905 of the β flap-tip helix to a serine, while the rpoC2064 mutation duplicated positions 415 to 416 (valine-isoleucine) at the base of the β' dock domain. These findings support previously published in vitro results, which have suggested that the β flap-tip helix and β' dock domain at either side of the RNA exit tunnel mediate the binding to NusA during transcriptional pausing and termination.

  • 84.
    Bystrom, Julia Wigren
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Näslund, Jonas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Europeiska CBRNE-centret.
    Trulsson, Fredrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Europeiska CBRNE-centret. Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Evander, Magnus
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi.
    Wesula Lwande, Olivia
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi.
    Ahlm, Clas
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Bucht, Göran
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Europeiska CBRNE-centret.
    Quantification and kinetics of viral RNA transcripts produced in Orthohantavirus infected cells2018Ingår i: Virology Journal, ISSN 1743-422X, E-ISSN 1743-422X, Vol. 15, s. 1-7, artikel-id 18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Rodent borne viruses of the Orthohantavirus genus cause hemorrhagic fever with renal syndrome among people in Eurasia, and hantavirus cardiopulmonary syndrome in the Americas. At present, there are no specific treatments or efficient vaccines against these diseases. Improved understanding of viral transcription and replication may instigate targeted treatment of Orthohantavirus infections. For this purpose, we investigated the kinetics and levels of viral RNA transcription during an ongoing infection in-vitro. Methods: Vero E6 cells were infected with Puumala Orthohantavirus (strain Kazan) before cells and supernatants were collected at different time points post infection for the detection of viral RNAs. A plasmid containing primer binding sites of the three Orthohantavirus segments small (S), medium (M) and large (L) was constructed and standard curves were generated to calculate the copy numbers of the individual transcripts in the collected samples. Results: Our results indicated a rapid increase in the copy number of viral RNAs after 9 h post infection. At peak days, 2-6 days after infection, the S- and M-segment transcripts became thousand and hundred-fold more abundant than the copy number of the L-segment RNA, respectively. The presence of viral RNA in the cell culture media was detected at later time-points. Conclusions: We have developed a method to follow RNA transcription in-vitro after synchronous infection of Vero cells. The obtained results may contribute to the understanding of the viral replication, and may have implications in the development of antiviral drugs targeting transcription or replication of negative stranded RNA viruses.

  • 85.
    Byström, Anders S
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Björk, Glenn R
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Chromosomal location and cloning of the gene (trmD) responsible for the synthesis of tRNA (m1G) methyltransferase in Escherichia coli K-12.1982Ingår i: Molecular General Genetics, ISSN 0026-8925, E-ISSN 1432-1874, Vol. 188, nr 3, s. 440-446Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The trmD gene, which governs the formation of 1-methyl-guanosine(m1G) in transfer ribonucleic acid (tRNA), has been located by phage P1 transduction at 56 min on the chromosomal map of Escherichia coli. Cotransduction to tyrA at 56 min is 80%. From the Clarke and Carbon collection a ColE1-tyrA+ hybrid plasmid was isolated, which carried the trmD+ gene and was shown to over-produce the tRNA(m1G)methyltransferase. By subcloning restriction enzyme fragments in vitro, the trmD+ gene was located to a 3.4 kb DNA fragment 6.5 kb clockwise from the tyrA+ gene. The mutation trmD1, which renders the tRNA(m1G)methyltransferase temperature-sensitive both in vivo and in vitro could be complemented by trmD+ plasmids. These results suggest that the gene trmD+ is the structural gene for the tRNA(m1G)methyltransferase (EC 2.1.1.3.1).

  • 86.
    Byström, Anders S
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Björk, Glenn R
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    The structural gene (trmD) for the tRNA(m1G)methyltransferase is part of a four polypeptide operon in Escherichia coli K-121982Ingår i: Molecular General Genetics, ISSN 0026-8925, E-ISSN 1432-1874, Vol. 188, nr 3, s. 447-454Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The trmD gene, which is the structural gene for the tRNA(m1G)-methyltransferase, is shown to be part of a polycistronic operon. A 4.6 kb SalI-EcoRI chromosomal DNA fragment contains the trmD gene (Byström and Björk 1982). Subclonings, deletion mapping and Tn5 insertions into plasmid pBY03 have established the gene organization of the trmD area on the Escherichia coli chromosome. The different plasmid derivatives were analysed for expression of protein products using the minicell system. Such analyses established the organisation of genes encoding six polypeptides to be SalI1-48 K-13 K-25 K-31 K-15 K-16 K-EcoRI1. The 31 K polypeptide was shown to be the tRNA(m1G)methyltransferase. The trmD operon encodes for four polypeptides; 13 K-25 K-31 K(trmD)-15 K and the direction of transcription is from 13 K (promoter proximal) to 15 K (promoter distal). However, there might be a weak internal promoter between the trmD gene and the gene encoding the 15 K product. The level of expression from this operon in the minicell system does not seem to follow normal polarity since we observed high expression of 13 K, 25 K, and 15 K products but low expression of the internal trmD gene.

  • 87.
    Byström, Anders S.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Fink, G. R.
    A functional analysis of the repeated methionine initiator tRNA genes (IMT) in yeast1989Ingår i: Molecular General Genetics, ISSN 0026-8925, E-ISSN 1432-1874, Vol. 216, nr 2-3, s. 276-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Standard laboratory yeast strains have from four to five genes encoding the methionine initiator tRNA (IMT). Strain S288C has four IMT genes with identical coding sequences that are colinear with the RNA sequence of tRNA(IMet). Each of the four IMT genes from strain S288C is located on a different chromosome. A fifth IMT gene with the same coding sequence is present in strain A364A but not in S288C. By making combinations of null alleles in strain S288C, we show that each of the four IMT genes is functional and that tRNA(IMet) is not limiting in yeast strains with three or more intact genes. Strains containing a single IMT2, 3 or 4 gene grow only after amplification of the remaining IMT gene. Strains with only the IMT1 gene intact are viable but grow extremely slow; normal growth is restored by the addition of another IMT gene by transformation, providing a direct test for IMT function.

  • 88.
    Byström, Anders S
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Hjalmarsson, Karin J
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Wikström, P Mikael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Björk, Glenn R
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    The nucleotide sequence of an Escherichia coli operon containing genes for the tRNA(m1G)methyltransferase, the ribosomal proteins S16 and L19 and a 21-K polypeptide1983Ingår i: EMBO Journal, ISSN 0261-4189, E-ISSN 1460-2075, Vol. 2, nr 6, s. 899-905Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nucleotide sequence of a 4.6-kb SalI-EcoRI DNA fragment including the trmD operon, located at min 56 on the Escherichia coli K-12 chromosome, has been determined. The trmD operon encodes four polypeptides: ribosomal protein S16 (rpsP), 21-K polypeptide (unknown function), tRNA-(m1G)methyltransferase (trmD) and ribosomal protein L19 (rplS), in that order. In addition, the 4.6-kb DNA fragment encodes a 48-K and a 16-K polypeptide of unknown functions which are not part of the trmD operon. The mol. wt. of tRNA(m1G)methyltransferase determined from the DNA sequence is 28 424. The probable locations of promoter and terminator of the trmD operon are suggested. The translational start of the trmD gene was deduced from the known NH2-terminal amino acid sequence of the purified enzyme. The intercistronic regions in the operon vary from 9 to 40 nucleotides, supporting the earlier conclusion that the four genes are co-transcribed, starting at the major promoter in front of the rpsP gene. Since it is known that ribosomal proteins are present at 8000 molecules/genome and the tRNA-(m1G)methyltransferase at only approximately 80 molecules/genome in a glucose minimal culture, some powerful regulatory device must exist in this operon to maintain this non-coordinate expression. The codon usage of the two ribosomal protein genes is similar to that of other ribosomal protein genes, i.e., high preference for the most abundant tRNA isoaccepting species. The trmD gene has a codon usage typical for a protein made in low amount in accordance with the low number of tRNA-(m1G)methyltransferase molecules found in the cell.

  • 89.
    Byström, Anders S
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    von Gabain, A
    Björk, Glenn R
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Differentially expressed trmD ribosomal protein operon of Escherichia coli is transcribed as a single polycistronic mRNA species1989Ingår i: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 208, nr 4, s. 575-586Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The trmD operon is a four-cistron operon in which the first and fourth genes encode ribosomal proteins S16 (rpsP) and L19 (rplS), respectively. The second gene encodes a 21,000 Mr polypeptide of unknown function and the third gene (trmD) encodes the enzyme tRNA(m1G37)methyltransferase, which catalyzes the formation of 1-methylguanosine (m1G) next to the 3' end of the anticodon (position 37) of some tRNAs in Escherichia coli. Here we show under all regulatory conditions studied, transcription initiates at one unique site, and the entire operon is transcribed into one polycistronic mRNA. Between the promoter and the first gene, rpsP, an attenuator-like structure is found (delta G = -18 kcal; 1 cal = 4.184 J), followed by four uridine residues. This structure is functional in vitro, and terminates more than two-thirds of the transcripts. The different parts of the trmD operon mRNA decay at a uniform rate. The stability of the trmD mRNA is not reduced with decreasing growth rate, which is in contrast to what has been found for other ribosomal protein mRNAs. Furthermore, earlier experiments have shown the existence of differential expression as well as non-co-ordinate regulation within the operon. Our results are consistent with the regulation of the trmD operon being due to some mechanism(s) operating at the post-transcriptional level, and do not involve differential degradation of different mRNA segments, internal promoters or internal terminators.

  • 90. Byström, Jonas
    et al.
    Thomson, Scott J.
    Johansson, Jörgen
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Edin, Matthew L.
    Zeldin, Darryl C.
    Gilroy, Derek W.
    Smith, Andrew M.
    Bishop-Bailey, David
    Inducible CYP2J2 and its product 11,12-EET promotes bacterial phagocytosis: a role for CYP2J2 deficiency in the pathogenesis of Crohn's disease?2013Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, nr 9, artikel-id e75107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The epoxygenase CYP2J2 has an emerging role in inflammation and vascular biology. The role of CYP2J2 in phagocytosis is not known and its regulation in human inflammatory diseases is poorly understood. Here we investigated the role of CYP2J2 in bacterial phagocytosis and its expression in monocytes from healthy controls and Crohns disease patients. CYP2J2 is anti-inflammatory in human peripheral blood monocytes. Bacterial LPS induced CYP2J2 mRNA and protein. The CYP2J2 arachidonic acid products 11,12-EET and 14,15-EET inhibited LPS induced TNFα release. THP-1 monocytes were transformed into macrophages by 48h incubation with phorbol 12-myristate 13-acetate. Epoxygenase inhibition using a non-selective inhibitor SKF525A or a selective CYP2J2 inhibitor Compound 4, inhibited E. coli particle phagocytosis, which could be specifically reversed by 11,12-EET. Moreover, epoxygenase inhibition reduced the expression of phagocytosis receptors CD11b and CD68. CD11b also mediates L. monocytogenes phagocytosis. Similar, to E. coli bioparticle phagocytosis, epoxygenase inhibition also reduced intracellular levels of L. monocytogenes, which could be reversed by co-incubation with 11,12-EET. Disrupted bacterial clearance is a hallmark of Crohn's disease. Unlike macrophages from control donors, macrophages from Crohn's disease patients showed no induction of CYP2J2 in response to E. coli. These results demonstrate that CYP2J2 mediates bacterial phagocytosis in macrophages, and implicates a defect in the CYP2J2 pathway may regulate bacterial clearance in Crohn's disease.

  • 91.
    Bölin, Ingrid
    Umeå universitet, Medicinska fakulteten, Mikrobiologi.
    Temperature-inducible and calcium-regulated proteins encoded by the virulence plasmid of Yersinia1987Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The pathogenic members of the genus Yersinia, Y. pseudotuberculosis, Y. pestis and Y. enterocolitica are transmitted from animals to man and may give rise to disease with a variety of symptoms. These bacteria possess related plasmids necessary for virulence. In this study, gene products encoded by the virulence plasmid have been identified and characterized.

    A temperature-inducible outer membrane protein YOP1, is encoded by the virulence plasmid. YOP1 is expressed by Y. pseudotuberculosis and Y. enterocolitica at 37°C. The genetic locale of trie structural gene for YOPl on the virulence plasmid was determined. A mutant that was unable to express this protein, remained fully virulent, showing that YOP1 is not a virulence determinant.

    Several other proteins encoded by the virulence plasmid are induced at 37°C in a medium lacking Ca2+. These proteins are not expressed at 26°C and expression is repressed by Ca2+-concentrations in excess of 2.5 mM. In Ca2+-deficient medium, the induced proteins can be found extracellu- larly as well as in the outer membrane. However, in the presence of Ca at 37°C they are only found in the outer membrane. The released proteins consist of eight polypeptides as revealed by two-dimensional electro­phoresis. These proteins, Y0P2a and 2b, YOP3, Y0P4a and 4b, the V-antigen and a small uncharacterized polypeptide, are expressed by all three pathogenic Yersinia species, both in vivo and in vitro.

    The Ca2+-controlled expression of the YOP proteins is regulated by genes in the Ca2+ -region, which are conserved in the three species. Mutations in this region repress the expression of the Ca2+-regulated YOPs. The genetic loci identified for five of these proteins revealed that only the structural gene of the Y0P4b protein is part of the Ca2+ -region. The other genes were found at separate locations outside this region. The structural genes for YOP4b, YOP3 and the V-antigen, together with the genes for two additional polypeptides, were localized to a common region conserved on the plasmids of the Yersinia species. The structural genes for Y0P2b (yopH) and Y0P5 (yopE) are located in different positions on the plasmid from Y. enterocolitica, compared to the other two species. This plasmid has Been rearranged so that these genes are located close to one another.

    The DNA sequence of the yopH gene shows that it is a singly transcrip­tional unit. Transcription of this gene is regulated by Ca2+-concentra­tion and by temperature. A mutant strain of Y. pseudo tuberculosis, de­leted for the yopH gene on the virulence plasmid, is avirulent In mice. Virulence is restored by trans-complementation with the cloned yopH gene. The mutant strain is also’ unable to inhibit phagocytosis of macrophages as compared to the wild-type strain. The trans-compleroented strain shows inhibition comparable to that of the wild-type. Therefore, the YOP2b protein is considered to be an essential virulence determinant.

  • 92.
    Caraballo, Rémi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Saleeb, Michael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Bauer, Johannes
    Interfaculty Institute of Biochemistry, University of Tübingen, Germany.
    Liaci, Antonio-Manuel
    Interfaculty Institute of Biochemistry, University of Tübingen, Germany.
    Chandra, Naresh
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Storm, Rickard J
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Frängsmyr, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Qian, Weixing
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Stehle, Thilo
    Interfaculty Institute of Biochemistry, University of Tübingen, Germany ; Department of Pediatrics, Vanderbilt University School of Medicine, USA.
    Arnberg, Niklas
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Virologi. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Elofsson, Mikael
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Triazole linker-based trivalent sialic acid inhibitors of adenovirus type 37 infection of human corneal epithelial cells2015Ingår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 13, nr 35, s. 9194-9205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adenovirus type 37 (Ad37) is one of the principal agents responsible for epidemic keratoconjunctivitis (EKC), a severe ocular infection that remains without any available treatment. Recently, a trivalent sialic acid derivative (ME0322, Angew. Chem. Int. Ed., 2011, 50, 6519) was shown to function as a highly potent inhibitor of Ad37, efficiently preventing the attachment of the virion to the host cells and subsequent infection. Here, new trivalent sialic acid derivatives were designed, synthesized and their inhibitory properties against Ad37 infection of the human corneal epithelial cells were investigated. In comparison to ME0322, the best compound (17a) was found to be over three orders of magnitude more potent in a cell-attachment assay (IC50 = 1.4 nM) and about 140 times more potent in a cell-infection assay (IC50 = 2.9nM). X-ray crystallographic analysis demonstrated a trivalent binding mode of all compounds to the Ad37 fiber knob. For the most potent compound ophthalmic toxicity in rabbits was investigated and it was concluded that repeated eye administration did not cause any adverse effects.

  • 93.
    Carlsson, Jan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Berglin, Ewa H.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Claesson, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Edlund, Maj-Britt K.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Persson, Sten
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Catalase inhibition by sulfide and hydrogen peroxide-induced mutagenicity in Salmonella typhimurium strain TA1021988Ingår i: Mutation research, ISSN 0027-5107, E-ISSN 1873-135X, Vol. 202, nr 1, s. 59-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The lethal and mutagenic effects of hydrogen peroxide were studied in exponentially growing cultures of Salmonella typhimurium strain TA102. Exposure of the cultures to non-lethal levels of sodium sulfide significantly increased the lethality and mutagenicity of hydrogen peroxide. The catalase activity was decreased in cells exposed to sodium sulfide, but there were no changes in the cellular levels of superoxide dismutase, glutathione reductase, or NADPH-dependent alkyl hydroperoxide reductase. Hydrogen peroxide-induced mutagenesis and killing of S. typhimurium strain TA102 in the presence of sulfide may in part be explained by an inactivation of catalase by sulfide.

  • 94. Castanheira, Sonia
    et al.
    Cestero, Juan J.
    Rico-Perez, Gadea
    Garcia, Pablo
    Cava, Felipe
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Ayala, Juan A.
    Graciela Pucciarelli, M.
    Garcia-del Portillo, Francisco
    A Specialized Peptidoglycan Synthase Promotes Salmonella Cell Division inside Host Cells2017Ingår i: mBio, ISSN 2161-2129, E-ISSN 2150-7511, Vol. 8, nr 6, artikel-id e01685-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bacterial cell division has been studied extensively under laboratory conditions. Despite being a key event in the bacterial cell cycle, cell division has not been explored in vivo in bacterial pathogens interacting with their hosts. We discovered in Salmonella enterica serovar Typhimurium a gene absent in nonpathogenic bacteria and encoding a peptidoglycan synthase with 63% identity to penicillin-binding protein 3 (PBP3). PBP3 is an essential cell division-specific peptidoglycan synthase that builds the septum required to separate daughter cells. Since S. Typhimurium carries genes that encode a PBP3 paralog-which we named PBP3(SAL)-and PBP3, we hypothesized that there are different cell division events in host and nonhost environments. To test this, we generated S. Typhimurium isogenic mutants lacking PBP3(SAL) or the hitherto considered essential PBP3. While PBP3 alone promotes cell division under all conditions tested, the mutant producing only PBP3(SAL) proliferates under acidic conditions (pH <= 5.8) but does not divide at neutral pH. PBP3(SAL) production is tightly regulated with increased levels as bacteria grow in media acidified up to pH 4.0 and in intracellular bacteria infecting eukaryotic cells. PBP3(SAL) activity is also strictly dependent on acidic pH, as shown by beta-lactam antibiotic binding assays. Live-cell imaging microscopy revealed that PBP3(SAL) alone is sufficient for S. Typhimurium to divide within phagosomes of the eukaryotic cell. Additionally, we detected much larger amounts of PBP3(SAL) than those of PBP3 in vivo in bacteria colonizing mouse target organs. Therefore, PBP3(SAL) evolved in S. Typhimurium as a specialized peptidoglycan synthase promoting cell division in the acidic intraphagosomal environment. IMPORTANCE During bacterial cell division, daughter cells separate by a transversal structure known as the division septum. The septum is a continuum of the cell wall and therefore is composed of membrane(s) and a peptidoglycan layer. To date, actively growing bacteria were reported to have only a "cell division-specific" peptidoglycan synthase required for the last steps of septum formation and consequently, essential for bacterial life. Here, we discovered that Salmonella enterica has two peptidoglycan synthases capable of synthesizing the division septum. One of these enzymes, PBP3(SAL), is present only in bacterial pathogens and evolved in Salmonella to function exclusively in acidic environments. PBP3(SAL) is used preferentially by Salmonella to promote cell division in vivo in mouse target organs and inside acidified phagosomes. Our data challenge the concept of only one essential cell division-specific peptidoglycan synthase and demonstrate that pathogens can divide in defined host locations using alternative mechanisms.

  • 95.
    Castelain, Mickaël
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ehlers, Sarah
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Klinth, Jeanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lindberg, Stina
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fast uncoiling kinetics of F1C pili expressed by uropathogenic Escherichia coli are revealed on a single pilus level using force-measuring optical tweezers2011Ingår i: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 40, nr 3, s. 305-316Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Uropathogenic Escherichia coli (UPEC) expressvarious kinds of organelles, so-called pili or fimbriae, thatmediate adhesion to host tissue in the urinary tract throughspecific receptor-adhesin interactions. The biomechanicalproperties of these pili have been considered important forthe ability of bacteria to withstand shear forces from rinsingurine flows. Force-measuring optical tweezers have beenused to characterize individual organelles of F1C typeexpressed by UPEC bacteria with respect to such properties.Qualitatively, the force-versus-elongation response wasfound to be similar to that of other types of helix-like piliexpressed by UPEC, i.e., type 1, P, and S, with force-inducedelongation in three regions, one of which represents theimportant uncoiling mechanism of the helix-like quaternarystructure. Quantitatively, the steady-state uncoiling forcewas assessed as 26.4 ±1.4 pN, which is similar to those ofother pili (which range from 21 pN for SI to 30 pN for type 1).The corner velocity for dynamic response (1,400 nm/s) wasfound to be larger than those of the other pili (400–700 nm/sfor S and P pili, and 6 nm/s for type 1). The kinetics werefound to be faster, with a thermal opening rate of 17 Hz, afew times higher than S and P pili, and three orders ofmagnitude higher than type 1. These data suggest that F1Cpili are, like P and S pili, evolutionarily selected to primarilywithstand the conditions expressed in the upper urinary tract.

  • 96.
    Cava, Felipe
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Biology of Vibrio cholerae: editorial overview2017Ingår i: International Microbiology, ISSN 1139-6709, E-ISSN 1618-1905, Vol. 20, nr 3Artikel i tidskrift (Övrigt vetenskapligt)
  • 97.
    Cava, Felipe
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Divergent functional roles of D-amino acids secreted by Vibrio cholerae2017Ingår i: International Microbiology, ISSN 1139-6709, E-ISSN 1618-1905, Vol. 20, nr 3, s. 149-150Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The L-forms of amino acids are used in all kingdoms of life to synthesize proteins. However, the bacterium Vibrio cholerae, the causative agent of cholera, produces D-amino acids which are released to the environment at millimolar concentrations. We baptized these D-amino acids as non-canonical D-amino acids (NCDAAs) since they are different from those (i.e. D-alanine and D-glutamate) normally present in the bacterial cell wall. In V. cholerae, production of NCDAAs relies on the BsrV enzyme, a periplasmic broad spectrum racemase. BsrV multispecific activity, produces of a wide range of distinct D-amino acids. Using a combination of genetics and molecular physiology approaches we have demonstrated that NCDAAs target different cellular processes which may function as part of a cooperative strategy in vibrio communities to protect non-producing members from competing bacteria. Because NCDAA production is widespread in bacteria, we anticipate that NCDAAs are relevant modulators of microbial subpopulations in diverse ecosystems.

  • 98.
    Cava, Felipe
    et al.
    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).
    de Pedro, Miguel A.
    Peptidoglycan plasticity in bacteria: emerging variability of the murein sacculus and their associated biological functions2014Ingår i: Current Opinion in Microbiology, ISSN 1369-5274, E-ISSN 1879-0364, Vol. 18, s. 46-53Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The peptidoglycan (PG) sacculus once thought to be just a reinforcing, static and uniform structure, is fast becoming recognized as a dynamic cell constituent involved in every aspect of bacterial physiology. Recent advances showed that in addition to 'classical' tasks - as an essential element to define bacterial shape, size, division and resistance to osmotic stress the sacculus plays very important roles in many other fields. The very few chemical and structural changes that were once considered as bizarre, or maybe exotic exceptions, are now universally accepted as fundamental pieces in bacterial cell wall adaptation to different kinds of environmental stresses; immune response; intra-specific and inter-specific signalling and antibiotics, just to mention a few. Most, if not all, of these implications are a consequence of the enormous adaptability of PG metabolism to cope with changing conditions, a characteristic for which the term plasticity is proposed. Here we overview and comment on a number of recent contributions on the cell wall adaptive responses to environmental challenges that has greatly impacted the already high complexity of the PG biology field. These new evidences have revived the interest in PG plasticity as an exciting and trendy topic in current microbiology which considers this variability as the trustworthy picture of bacterial PG in nature.

  • 99.
    Cava, Felipe
    et al.
    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).
    Kuru, Erkin
    Brun, Yves V.
    de Pedro, Miguel A.
    Modes of cell wall growth differentiation in rod-shaped bacteria2013Ingår i: Current Opinion in Microbiology, ISSN 1369-5274, E-ISSN 1879-0364, Vol. 16, nr 6, s. 731-737Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A bacterial cell takes on the challenge to preserve and reproduce its shape at every generation against a substantial internal pressure by surrounding itself with a mechanical support, a peptidoglycan cell wall. The enlargement of the cell wall via net incorporation of precursors into the pre-existing wall conditions bacterial growth and morphology. However, generation, reproduction and/or modification of a specific shape requires that the incorporation takes place at precise locations for a defined time period. Much has been learnt in the past few years about the biochemistry of the peptidoglycan synthesis process, but topological approaches to the understanding of shape generation have been hindered by a lack of appropriate techniques. Recent technological advances are paving the way for substantial progress in understanding the mechanisms of bacterial morphogenesis. Here we review the latest developments, focusing on the impact of new techniques on the precise mapping of cell wall growth sites.

  • 100. Champion, Mia D
    et al.
    Zeng, Qiandong
    Nix, Eli B
    Nano, Francis E
    Keim, Paul
    Kodira, Chinnappa D
    Borowsky, Mark
    Young, Sarah
    Koehrsen, Michael
    Engels, Reinhard
    Pearson, Matthew
    Howarth, Clint
    Larson, Lisa
    White, Jared
    Alvarado, Lucia
    Forsman, Mats
    Totalförsvarets forskninginstitut, Umeå Sweden FOI.
    Bearden, Scott W
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Titball, Richard
    Michell, Stephen L
    Birren, Bruce
    Galagan, James
    Comparative genomic characterization of Francisella tularensis strains belonging to low and high virulence subspecies2009Ingår i: PLoS pathogens, ISSN 1553-7374, Vol. 5, nr 5, s. e1000459-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tularemia is a geographically widespread, severely debilitating, and occasionally lethal disease in humans. It is caused by infection by a gram-negative bacterium, Francisella tularensis. In order to better understand its potency as an etiological agent as well as its potential as a biological weapon, we have completed draft assemblies and report the first complete genomic characterization of five strains belonging to the following different Francisella subspecies (subsp.): the F. tularensis subsp. tularensis FSC033, F. tularensis subsp. holarctica FSC257 and FSC022, and F. tularensis subsp. novicida GA99-3548 and GA99-3549 strains. Here, we report the sequencing of these strains and comparative genomic analysis with recently available public Francisella sequences, including the rare F. tularensis subsp. mediasiatica FSC147 strain isolate from the Central Asian Region. We report evidence for the occurrence of large-scale rearrangement events in strains of the holarctica subspecies, supporting previous proposals that further phylogenetic subdivisions of the Type B clade are likely. We also find a significant enrichment of disrupted or absent ORFs proximal to predicted breakpoints in the FSC022 strain, including a genetic component of the Type I restriction-modification defense system. Many of the pseudogenes identified are also disrupted in the closely related rarely human pathogenic F. tularensis subsp. mediasiatica FSC147 strain, including modulator of drug activity B (mdaB) (FTT0961), which encodes a known NADPH quinone reductase involved in oxidative stress resistance. We have also identified genes exhibiting sequence similarity to effectors of the Type III (T3SS) and components of the Type IV secretion systems (T4SS). One of the genes, msrA2 (FTT1797c), is disrupted in F. tularensis subsp. mediasiatica and has recently been shown to mediate bacterial pathogen survival in host organisms. Our findings suggest that in addition to the duplication of the Francisella Pathogenicity Island, and acquisition of individual loci, adaptation by gene loss in the more recently emerged tularensis, holarctica, and mediasiatica subspecies occurred and was distinct from evolutionary events that differentiated these subspecies, and the novicida subspecies, from a common ancestor. Our findings are applicable to future studies focused on variations in Francisella subspecies pathogenesis, and of broader interest to studies of genomic pathoadaptation in bacteria.

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