| 1. |
- Avican, Ummehan, et al.
(författare)
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The Tat substrate SufI is critical for the ability of Yersinia pseudotuberculosis to cause systemic infection
- 2017
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 85:4
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Tidskriftsartikel (refereegranskat)abstract
- The twin arginine translocation (Tat) system targets folded proteins across the inner membrane and is crucial for virulence in many important humanpathogenic bacteria. Tat has been shown to be required for the virulence of Yersinia pseudotuberculosis, and we recently showed that the system is critical for different virulence-related stress responses as well as for iron uptake. In this study, we wanted to address the role of the Tat substrates in in vivo virulence. Therefore, 22 genes encoding potential Tat substrates were mutated, and each mutant was evaluated in a competitive oral infection of mice. Interestingly, a.sufI mutant was essentially as attenuated for virulence as the Tat-deficient strain. We also verified that SufI was Tat dependent for membrane/periplasmic localization in Y. pseudotuberculosis. In vivo bioluminescent imaging of orally infected mice revealed that both the.sufI and Delta tatC mutants were able to colonize the cecum and Peyer's patches (PPs) and could spread to the mesenteric lymph nodes (MLNs). Importantly, at this point, neither the Delta tatC mutant nor the Delta sufI mutant was able to spread systemically, and they were gradually cleared. Immunostaining of MLNs revealed that both the Delta tatC and Delta sufI mutants were unable to spread from the initial infection foci and appeared to be contained by neutrophils, while wild-type bacteria readily spread to establish multiple foci from day 3 postinfection. Our results show that SufI alone is required for the establishment of systemic infection and is the major cause of the attenuation of the Delta tatC mutant.
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| 2. |
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| 3. |
- Bunikis, Ignas, 1981-, et al.
(författare)
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An RND-type efflux system in Borrelia burgdorferi is involved in virulence and resistance to antimicrobial compounds
- 2008
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Ingår i: PLoS Pathogenicity. - 1553-7374. ; 4:2, s. e1000009-
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Tidskriftsartikel (refereegranskat)abstract
- Borrelia burgdorferi is remarkable for its ability to thrive in widely different environments due to its ability to infect various organisms. In comparison to enteric Gram-negative bacteria, these spirochetes have only a few transmembrane proteins some of which are thought to play a role in solute and nutrient uptake and excretion of toxic substances. Here, we have identified an outer membrane protein, BesC, which is part of a putative export system comprising the components BesA, BesB and BesC. We show that BesC, a TolC homolog, forms channels in planar lipid bilayers and is involved in antibiotic resistance. A besC knockout was unable to establish infection in mice, signifying the importance of this outer membrane channel in the mammalian host. The biophysical properties of BesC could be explained by a model based on the channel-tunnel structure. We have also generated a structural model of the efflux apparatus showing the putative spatial orientation of BesC with respect to the AcrAB homologs BesAB. We believe that our findings will be helpful in unraveling the pathogenic mechanisms of borreliae as well as in developing novel therapeutic agents aiming to block the function of this secretion apparatus.
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| 4. |
- Bunikis, J, et al.
(författare)
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Surface exposure and species specificity of an immunoreactive domain of a 66-kilodalton outer membrane protein (P66) of the Borrelia spp. that cause Lyme disease
- 1996
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 64:12, s. 5111-5116
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Tidskriftsartikel (refereegranskat)abstract
- A chromosomally encoded 66-kDa protein (P66) of Borrelia spp. that cause Lyme disease has previously been shown to be associated with the spirochetal outer membrane. A topological model of P66 predicts a surface-exposed fragment which links the N- and C-terminal intramembranous domains of the protein (J. Bunikis, L. Noppa, and S. Bergström, FEMS Microbiol. Lett. 131:139-145, 1995). In the present study, an immunogenic determinant of P66 was identified by a comparison of the immunoreactivities of different fragments of P66 generated either by proteolytic treatment of intact spirochetes or as recombinant proteins expressed in Escherichia coli. The immune response to P66 during natural infection was found to be directed against the predicted surface domain which comprises amino acids at positions 454 through 491. A sequence comparison revealed considerable polymorphism of the surface domains of P66 proteins of different Lyme disease-causing Borrelia species. Five sequence patterns of this domain were observed in the B. garinii strains studied. In contrast, sequences of the relevant part of P66 of the B. afzelii and B. burgdorferi sensu stricto isolates studied were identical within the respective species. In immunoblotting, 5 of 17 (29.4%) sera from North American patients with early disseminated or persistent Lyme disease reacted against P66 of B. burgdorferi sensu stricto B31. These sera, however, failed to recognize P66 of B. afzelii and B. garinii, as well as an analog of P66 in the relapsing fever agent, B. hermsii. In conclusion, the topological model of P66 is supported by the demonstration of an apparent surface localization of an immunoreactive domain of this protein. Furthermore, analogous to the plasmid-encoded borrelial outer surface proteins, the predicted surface-exposed portion of chromosomally encoded P66 appears to be antigenically heterogenous.
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| 5. |
- Dahlqvist, Solbritt Rantapää, et al.
(författare)
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Acetylator phenotypes in primary Sjögren's syndrome
- 1994
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Ingår i: British Journal of Rheumatology. - : Oxford University Press (OUP). - 0263-7103 .- 1460-2172. ; 33:4, s. 405-406
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Tidskriftsartikel (refereegranskat)
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| 6. |
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| 7. |
- Gylfe, Åsa, et al.
(författare)
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Isolation of Lyme disease Borrelia from puffins (Fratercula arctica) and seabird ticks (Ixodes uriae) on the Faeroe Islands
- 1999
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Ingår i: Journal of Clinical Microbiology. - 0095-1137 .- 1098-660X. ; 37:4, s. 890-896
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Tidskriftsartikel (refereegranskat)abstract
- This is the first report on the isolation of Lyme disease Borrelia from seabirds on the Faeroe Islands and the characteristics of its enzootic cycle. The major components of the Borrelia cycle include the puffin (Fratercula arctica) as the reservoir and Ixodes uriae as the vector. The importance of this cycle and its impact on the spread of human Lyme borreliosis have not yet been established. Borrelia spirochetes isolated from 2 of 102 sampled puffins were compared to the borreliae previously obtained from seabird ticks, I. uriae. The rrf-rrl intergenic spacer and the rrs and the ospC genes were sequenced and a series of phylogenetic trees were constructed. Sequence data and restriction fragment length polymorphism analysis grouped the strains together with Borrelia garinii. In a seroepidemiological survey performed with residents involved in puffin hunting on the Faeroe Islands, 3 of 81 serum samples were found to be positive by two commonly used clinical tests: a flagellin-based enzyme-linked immunosorbent assay (ELISA) and Western blotting. These three positive serum samples also had high optical density values in a whole-cell ELISA. The finding of seropositive Faeroe Islanders who are regularly exposed to I. uriae indicate that there may be a transfer of B. garinii by this tick species to humans.
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| 8. |
- Nilsson, Carol L, et al.
(författare)
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Characterization of the P13 membrane protein of Borrelia burgdorferi by mass spectrometry.
- 2002
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Ingår i: Journal of the American Society for Mass Spectrometry. - 1044-0305 .- 1879-1123. ; 13:4, s. 295-299
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Tidskriftsartikel (refereegranskat)abstract
- Borrelia burgdorferi sensu lato is a tick-borne pathogen that causes Lyme disease. The characterization of membrane proteins from this and other pathogens may yield a better understanding of the mechanisms of infection and information useful for vaccine design. Characterization of the highly hydrophobic Borrelia outer membrane component P13 from a mutant (OspA- OspB- OspC- and OspD-) strain was undertaken by use of a combination of mass spectrometric methods. In a previous investigation, an electrospray ionization (ESI) mass spectrum of the intact protein provided an average molecular weight that was 20 Da lower than the predicted molecular weight. The mass deviation could be explained by a modification of the N-terminus of the protein such as pyroglutamylation (-17 Da) in combination with the experimental error of measurement, however more information was required. New structural information for this membrane protein was provided by peptide mapping with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) and sequencing with ESI-quadrupole-TOF tandem MS.
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| 9. |
- Noppa, Laila, et al.
(författare)
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P13, an integral membrane protein of Borrelia burgdorferi, is C-terminally processed and contains surface-exposed domains
- 2001
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 69:5, s. 3323-3334
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Tidskriftsartikel (refereegranskat)abstract
- To elucidate antigens present on the bacterial surface of Borrelia burgdorferi sensu lato that may be involved in pathogenesis, we characterized a protein, P13, with an apparent molecular mass of 13 kDa. The protein was immunogenic and was expressed in large amounts during in vitro cultivation compared to other known antigens. An immunofluorescence assay, immunoelectron microscopy, and protease sensitivity assays indicated that P13 is surface exposed. The deduced sequence of the P13 peptide revealed a possible signal peptidase type I cleavage site, and computer analysis predicted that P13 is an integral membrane protein with three transmembrane-spanning domains. Mass spectrometry, in vitro translation, and N- and C-terminal amino acid sequencing analyses indicated that P13 was posttranslationally processed at both ends and modified by an unknown mechanism. Furthermore, p13 belongs to a gene family with five additional members in B. burgdorferi sensu stricto. The p13 gene is located on the linear chromosome of the bacterium, in contrast to five paralogous genes, which are located on extrachromosomal plasmids. The size of the p13 transcript was consistent with a monocistronic transcript. This new gene family may be involved in functions that are specific for this spirochete and its pathogenesis.
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| 10. |
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| 11. |
- Park, Hyun-Sook, et al.
(författare)
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Novel role for a bacterial nucleoid protein in translation of mRNAs with suboptimal ribosome-binding sites
- 2010
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Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 24:13, s. 1345-1350
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Tidskriftsartikel (refereegranskat)abstract
- In Escherichia coli, the major nucleoid protein H-NS limits transcription by acting as a repressor or transcriptional silencer, presumably by its ability to close the looped chromosome domains in the nucleoid through DNA-protein-DNA bridging. Here, we demonstrate the direct involvement of H-NS as a positive factor stimulating translation of the malT mRNA. In vitro studies showed that H-NS facilitates a repositioning of the 30S preinitiation complex on the malT mRNA. H-NS stimulation of translation depended on the AU-rich -35 to -40 region of the mRNA. Several additional examples were found demonstrating a novel function for H-NS in translation of genes with suboptimal ribosome-binding sequences.
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| 12. |
- Pinne, Marija, et al.
(författare)
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Molecular analysis of the channel-forming protein P13 and its paralogue family 48 from different Lyme disease Borrelia species
- 2004
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 150:Pt 3, s. 549-559
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Tidskriftsartikel (refereegranskat)abstract
- The aetiological agent of Lyme disease, Borrelia burgdorferi cycles between its tick vector and mammalian hosts, implying that it can sense different environments and consequently change the expression of genes encoding several surface-associated proteins. The genome of the type strain B. burgdorferi B31 has revealed 175 different gene families. The p13 gene, situated on the chromosome, encodes a channel-forming protein that belongs to the gene family 48 consisting of eight additional paralogous genes. The heterogeneity of the P13 protein from different Lyme disease Borrelia strains was investigated. The predicted surface-exposed domains are the most heterogeneous regions and contain probable epitopes of P13. The membrane-spanning architecture of P13 was determined and a model for the location of this protein in the outer membrane is presented. The transcription of the paralogues of gene family 48 during in vitro culturing and in a mouse infection model was also analysed. The bba01 gene is the only p13 paralogue present in all three Lyme-disease-causing genospecies; it is stable during cultivation in vitro and the BBA01 protein was expressed in all Borrelia strains investigated. Conversely, paralogues bbi31, bbq06 and bbh41 were only detected in B. burgdorferi and the corresponding plasmids harbouring bbi31 and bbh41 were lost during in vitro passage. Finally, p13 and bbi31 are the only members of gene family 48 that are transcribed in mice, suggesting their importance during mammalian infection.
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| 13. |
- Östberg, Yngve, et al.
(författare)
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Elimination of channel-forming activity by insertional inactivation of the p13 gene in Borrelia burgdorferi
- 2002
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 184:24, s. 6811-6819
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Tidskriftsartikel (refereegranskat)abstract
- P13 is a chromosomally encoded 13-kDa integral outer membrane protein of the Lyme disease agent, Borrelia burgdorferi. The aim of this study was to investigate the function of the P13 protein. Here, we inactivated the p13 gene by targeted mutagenesis and investigated the porin activities of outer membrane proteins by using lipid bilayer experiments. Channel-forming activity was lost in the p13 mutant compared to wild-type B. burgdorferi, indicating that P13 may function as a porin. We purified native P13 to homogeneity by fast performance liquid chromatography and demonstrated that pure P13 has channel-forming activity with a single-channel conductance in 1 M KCl of 3.5 nS, the same as the porin activity that was lost in the p13 mutant. Further characterization of the channel formed by P13 suggested that it is cation selective and voltage independent. In addition, no major physiological effects of the inactivated p13 gene could be detected under normal growth conditions. The inactivation of p13 is the first reported inactivation of a gene encoding an integral outer membrane protein in B. burgdorferi. Here, we describe both genetic and biophysical experiments indicating that P13 in B. burgdorferi is an outer membrane protein with porin activity.
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| 14. |
- Östberg, Yngve, et al.
(författare)
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Functional analysis of a lipid galactosyltransferase synthesizing the major envelope lipid in the Lyme disease spirochete Borrelia burgdorferi.
- 2007
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Ingår i: FEMS Microbiol Lett. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 272:1, s. 22-9
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- One of the major lipids in the membranes of Borrelia burgdorferi ismonogalactosyl diacylglycerol (MGalDAG), a glycolipid recently shown to carryantigenic potency. Herein, it is shown that the gene mgs (TIGR designationbb0454) of B. burgdorferi encodes for the protein bbMGS that, when expressed inEscherichia coli, catalyzes the glycosylation of 1,2-diacylglycerol withspecificity for the donor substrate UDP-Gal yielding MGalDAG. Related lipidenzymes were found in many Gram-positive bacteria. The presence of thisgalactosyltransferase activity and synthesis of a cholesteryl galactoside byanother enzyme were verified in B. burgdorferi cell extract. Besides MGalDAG,phosphatidylcholine, phosphatidylglycerol, and cholesterol were also found asmajor lipids in the cell envelope. The high isoelectric point of bbMGS andclustered basic residues in its amino acid sequence suggest that the enzymeinteracts with acidic lipids in the plasma membrane, in agreement with strongenzymatic activation of bbMGS by phosphatidylglycerol. The membrane packing andimmunological properties of MGalDAG are likely to be of great importance in vivo.
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| 15. |
- Östberg, Yngve, et al.
(författare)
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Pleiotropic effects of inactivating a carboxyl-terminal protease, CtpA, in Borrelia burgdorferi
- 2004
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Ingår i: Journal of Bacteriology. - : Microbiology Society. - 0021-9193 .- 1098-5530. ; 186:7, s. 2074-2084
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Tidskriftsartikel (refereegranskat)abstract
- The aetiological agent of Lyme disease, Borrelia burgdorferi cycles between its tick vector and mammalian hosts, implying that it can sense different environments and consequently change the expression of genes encoding several surface-associated proteins. The genome of the type strain B. burgdorferi B31 has revealed 175 different gene families. The p13 gene, situated on the chromosome, encodes a channel-forming protein that belongs to the gene family 48 consisting of eight additional paralogous genes. The heterogeneity of the P13 protein from different Lyme disease Borrelia strains was investigated. The predicted surface-exposed domains are the most heterogeneous regions and contain probable epitopes of P13. The membrane-spanning architecture of P13 was determined and a model for the location of this protein in the outer membrane is presented. The transcription of the paralogues of gene family 48 during in vitro culturing and in a mouse infection model was also analysed. The bba01 gene is the only p13 paralogue present in all three Lyme-disease-causing genospecies; it is stable during cultivation in vitro and the BBA01 protein was expressed in all Borrelia strains investigated. Conversely, paralogues bbi31, bbq06 and bbh41 were only detected in B. burgdorferi and the corresponding plasmids harbouring bbi31 and bbh41 were lost during in vitro passage. Finally, p13 and bbi31 are the only members of gene family 48 that are transcribed in mice, suggesting their importance during mammalian infection.
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| 16. |
- Östberg, Yngve, et al.
(författare)
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The etiological agent of Lyme disease, Borrelia burgdorferi, appears to contain
- 2004
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 186:24, s. 8472-8477
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Tidskriftsartikel (refereegranskat)abstract
- Small regulatory RNAs (sRNAs) have recently been shown to be the main controllers of several regulatory pathways. The function of sRNAs depends in many cases on the RNA-binding protein Hfq, especially for sRNAs with an antisense function. In this study, the genome of Borrelia burgdorferi was subjected to different searches for sRNAs, including direct homology and comparative genomics searches and ortholog- and annotation-based search strategies. Two new sRNAs were found, one of which showed complementarity to the rpoS region, which it possibly controls by an antisense mechanism. The role of the other sRNA is unknown, although observed complementarities against particular mRNA sequences suggest an antisense mechanism. We suggest that the low level of sRNAs observed in B. burgdorferi is at least partly due to the presumed lack of both functional Hfq protein and RNase E activity.
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