bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inactivation of
ibeA
and
ibeT
Results in Decreased Expression of Type 1 Fimbriae in Extraintestinal Pathogenic
Escherichia coli
Strain BEN2908
Authors: Cortes Mélanie A. M. , Gibon Julien , Chanteloup Nathalie K. , Moulin-Schouleur Maryvonne , Gilot Philippe , Germon Pierre 
Published: July 2008

ABSTRACT

IbeA in extraintestinal pathogenic
Escherichia coli
(ExPEC) strains was previously described for its role in invasion. Here we investigated the role of IbeA and IbeT, encoded by a gene located downstream of
ibeA
, in the adhesion of the avian ExPEC strain BEN2908 to human brain microvascular endothelial cells (HBMEC). The Δ
ibeA
mutant was less adhesive to HBMEC than the wild-type strain BEN2908 was. Because strain BEN2908 also expresses type 1 fimbriae, we measured the adhesion specifically due to IbeA by comparing the adhesive properties of a Δ
fim
derivative of strain BEN2908 to those of a double Δ
fim
Δ
ibeA
mutant. No differences were observed, indicating that the reduction of adhesion in BEN2908 Δ
ibeA
could be due to a decrease in type 1 fimbria expression. We indeed showed that the decreased adhesion of BEN2908 Δ
ibeA
was correlated with a decrease in type 1 fimbria expression. Accordingly, more bacteria had a
fim
promoter orientated in the off position in a culture of BEN2908 Δ
ibeA
than in a culture of BEN2908. Expression of
fimB
and
fimE
, two genes encoding recombinases participating in controlling the orientation of the
fim
promoter, was decreased in BEN2908 Δ
ibeA
. A reduction of type 1 fimbria expression due to a preferential orientation of the
fim
promoter in the off position was also seen in an
ibeT
mutant of strain BEN2908. We finally suggest a role for IbeA and IbeT in modulating the expression of type 1 fimbriae through an as yet unknown mechanism.
Fine Antigenic Specificity and Cooperative Bactericidal Activity of Monoclonal Antibodies Directed at the Meningococcal Vaccine Candidate Factor H-Binding Protein
Authors: Beernink Peter T. , Welsch Jo Anne , Bar-Lev Michal , Koeberling Oliver , Comanducci Maurizio , Granoff Dan M. 
Published: July 2008

ABSTRACTNo broadly protective vaccine is available for the prevention of group B meningococcal disease. One promising candidate is factor H-binding protein (fHbp), which is present in all strains but often sparsely expressed. We prepared seven murine immunoglobulin G monoclonal antibodies (MAbs) against fHbp from antigenic variant group 2 (v.2) or v.3 (∼40% of group B strains). Although none of the MAbs individually elicited bactericidal activity with human complement, all had activity in different combinations. We used MAb reactivity with strains expressing fHbp polymorphisms and site-specific mutagenesis to identify residues that are important for epitopes recognized by six of the v.2 or v.3 MAbs and by two v.1 MAbs that were previously characterized. Residues affecting v.2 or v.3 epitopes resided between amino acids 174 and 216, which formed an eight-stranded beta-barrel in the C domain, while residues affecting the v.1 epitopes included amino acids 121 and 122 of the B domain. Pairs of MAbs were bactericidal when their respective epitopes involved residues separated by 16 to 20 Å and when at least one of the MAbs inhibited the binding of fH, a downregulatory complement protein. In contrast, there was no cooperative bactericidal activity when the distance between residues was ≥27 Å or ≤14 Å, which correlated with the inhibition of the binding of one MAb by the other MAb. Thus, a model for anti-fH MAb bactericidal activity against strains expressing low levels of fHbp requires the binding of two MAbs directed at nonoverlapping epitopes, which activates the classical complement pathway as well as inhibits fH binding. The latter increases the susceptibility of the organism to complement-mediated bacteriolysis.
Phenotypic Switching inCryptococcus neoformansContributes to Virulence by Changing the Immunological Host Response
Authors: Guerrero Abraham , Fries Bettina C. 
Published: July 2008

ABSTRACTCryptococcus neoformansis an encapsulated opportunistic organism that can undergo phenotypic switching. In this process, the parent smooth colony (SM) switches to a more virulent mucoid colony (MC) variant. The host responses mounted against the SM and MC variants differ, and lower tissue interleukin 10 (IL-10) levels are consistently observed in lungs of MC-infected C57BL/6 and BALB/c mice. This suggested different roles of this cytokine in SM and MC infections. The objective of this study was to compare survival rates and characterize the host responses of SM- and MC-infected IL-10-depleted (IL-10−/−) mice, which exhibit a Th1-polarized immune response and are considered resistant hosts. As expected, SM-infected IL-10−/−mice survived longer than wild-type mice, whereas MC-infected IL-10−/−mice did not exhibit a survival benefit. Consistent with this observation, we demonstrated marked differences in the inflammatory responses of SM- and MC-infected IL-10−/−and wild-type mice. This included a more Th1-polarized inflammatory response with enhanced recruitment of macrophages and natural killer and CD8 cells in MC- than in SM-infected IL-10−/−and wild-type mice. In contrast, both SM-infected IL-10−/−and wild-type mice exhibited higher recruitment of CD4 cells, consistent with enhanced survival and differences in recruitment and Th1/Th2 polarization. Lung tissue levels of IL-21, IL-6, IL-4, transforming growth factor beta, IL-12, and gamma interferon were higher in MC-infected IL-10−/−and wild-type mice than in SM-infected mice, whereas tumor necrosis factor alpha levels were higher in SM-infected IL-10−/−mice. In conclusion, the MC variant elicits an excessive inflammatory response in a Th1-polarized host environment, and therefore, the outcome is negatively affected by the absence of IL-10.
Pmp-Like Proteins Pls1 and Pls2 Are Secreted into the Lumen of the
Chlamydia trachomatis
Inclusion
Authors: Jorgensen Ine , Valdivia Raphael H. 
Published: July 2008

ABSTRACT

The obligate intracellular pathogen
Chlamydia trachomatis
secretes effector proteins across the membrane of the pathogen-containing vacuole (inclusion) to modulate host cellular functions. In an immunological screen for secreted chlamydial proteins, we identified CT049 and CT050 as potential inclusion membrane-associated proteins. These acidic, nonglobular proteins are paralogously related to the passenger domain of the polymorphic membrane protein PmpC and, like other Pmp proteins, are highly polymorphic among
C. trachomatis
ocular and urogenital strains. We generated antibodies to these Pmp-like secreted (Pls) proteins and determined by immunofluorescence microscopy that Pls1 (CT049) and Pls2 (CT050) localized to globular structures within the inclusion lumen and at the inclusion membrane. Fractionation of membranes and cytoplasmic components from infected cells by differential and density gradient centrifugation further indicated that Pls1 and Pls2 associated with membranes distinct from the bulk of bacterial and inclusion membranes. The accumulation of Pls1 and, to a lesser extent, Pls2 in the inclusion lumen was insensitive to the type III secretion inhibitor C1, suggesting that this translocation system is not essential for Pls protein secretion. In contrast, Pls secretion and stability were sensitive to low levels of β-lactam antibiotics, suggesting that a functional cell wall is required for Pls secretion from the bacterial cell. Finally, we tested the requirement for these proteins in
Chlamydia
infection by microinjecting anti-Pls1 and anti-Pls2 antibodies into infected cells. Coinjection of anti-Pls1 and -Pls2 antibodies partially inhibited expansion of the inclusion. Because Pls proteins lack classical
sec
-dependent secretion signals, we propose that Pls proteins are secreted into the inclusion lumen by a novel mechanism to regulate events important for chlamydial replication and inclusion expansion.
AMycobacterium tuberculosisRpf Double-Knockout Strain Exhibits Profound Defects in Reactivation from Chronic Tuberculosis and Innate Immunity Phenotypes
Authors: Russell-Goldman Eleanor , Xu Jiayong , Wang Xiaobing , Chan John , Tufariello JoAnn M. 
Published: July 2008

ABSTRACTResuscitation-promoting factors (Rpfs), apparent peptidoglycan hydrolases, have been implicated in the reactivation of dormant bacteria. We previously demonstrated that deletion ofrpfBimpaired reactivation ofMycobacterium tuberculosisin a mouse model. BecauseM. tuberculosisencodes five Rpf paralogues, redundant functions among the family members might obscurerpfsingle-knockout phenotypes. A series ofrpfdouble knockouts were therefore generated. One double mutant, ΔrpfAB, exhibited several striking phenotypes. Consistent with the proposed cell wall-modifying function of Rpfs, ΔrpfABexhibited an altered colony morphology. Although ΔrpfABgrew comparably to the parental strain in axenic culture, in vivo it exhibited deficiency in reactivation induced in C57BL/6 mice by the administration of nitric oxide synthase inhibitor (aminoguanidine) or by CD4+T-cell depletion. Notably, the reactivation deficiency of ΔrpfABwas more severe than that of ΔrpfBin aminoguanidine-treated mice. A similar deficiency was observed in ΔrpfABreactivation from a drug-induced apparently sterile state in infected NOS2−/−mice upon cessation of antimycobacterial therapy. Secondly, ΔrpfABshowed a persistence defect not seen with the ΔrpfBor ΔrpfAsingle mutants. Interestingly, ΔrpfABexhibited impaired growth in primary mouse macrophages and induced higher levels of the proinflammatory cytokines tumor necrosis factor alpha and interleukin 6. Simultaneous reintroduction ofrpfAandrpfBinto the double-knockout strain complemented the colony morphology and macrophage cytokine secretion phenotypes. Phenotypes related to cell wall composition and macrophage responses suggest thatM. tuberculosisRpfs may influence the outcome of reactivation, in part, by modulating innate immune responses to the bacterium.
Evaluation of a New Etest Vancomycin-Teicoplanin Strip for Detection of Glycopeptide-Intermediate
Staphylococcus aureus
(GISA), in Particular, Heterogeneous GISA
Authors: Yusof Anne , Engelhardt Anette , Karlsson Åsa , Bylund Lina , Vidh Pamela , Mills Karen , Wootton Mandy , Walsh Timothy R. 
Published: July 2008

ABSTRACT

Glycopeptide-intermediate
Staphylococcus aureus
(GISA) and, in particular, heterogeneous GISA (hGISA) are difficult to detect by standard MIC methods, and thus, an accurate detection method for clinical practice and surveillances is needed. Two prototype Etest strips designed for hGISA/GISA resistance detection (GRD) were evaluated using a worldwide collection of hGISA/GISA strains covering the five major clonal lineages. A total of 150 strains comprising 15 GISA and 60 hGISA strains (defined by population analysis profiles-area under the curve [PAP-AUC]), 70 glycopeptide-susceptible
S. aureus
(GSSA) strains, and 5
S. aureus
ATCC reference strains were tested. For standardized Etest vancomycin (VA) MIC testing, the modified Etest macromethod with VA and teicoplanin (TP) strips tested with a heavier inoculum using brain heart infusion agar (BHI) and two glycopeptide screening agar plates (6 μg/ml VA/BHI and 5 μg/ml Mueller-Hinton agar [MHA]) were tested in parallel with the two new Etest GRD strips: a VA 32 (0.5-μg/ml)-TP 32 (0.5-μg/ml) double-sided gradient (E-VA/TP) with one prototype overlaid with a nutrient (E-VA/TP+S) to enhance the growth of hGISA. The Etest GRD strips were tested with a standard 0.5-McFarland standard inoculum using MHA and MHA plus 5% blood (MHB) and were read at 18 to 24 and 48 h. The interpretive MIC cutoffs used for the new Etest GRD strips at 24 and 48 h were as follows: for GISA, TP or VA, ≥8, and a standard VA MIC of ≥6; for hGISA, TP or VA, ≥8, and a standard VA MIC of ≤4. The results on MHB at 48 h showed that E-VA/TP+S had high specificity (94%) and sensitivity (95%) in comparison to PAP-AUC and was able to detect all GISA (
n
= 15) and 98% of hGISA (
n
= 60) strains. In contrast, the glycopeptide screening plates performed poorly for hGISA. The new Etest GRD strip (E-VA/TP+S), utilizing standard media and inocula, is a simple and acceptable tool for detection of hGISA/GISA for clinical and epidemiologic purposes.
Molecular Defects Caused by Temperature-Sensitive Mutations in Semliki Forest Virus nsP1
Authors: Lulla Valeria , Sawicki Dorothea L. , Sawicki Stanley G. , Lulla Aleksei , Merits Andres , Ahola Tero 
Published: July 2008

ABSTRACT

Alphavirus replicase protein nsP1 has multiple functions during viral RNA synthesis. It catalyzes methyltransferase and guanylyltransferase activities needed in viral mRNA capping, attaches the viral replication complex to cytoplasmic membranes, and is required for minus-strand RNA synthesis. Two temperature-sensitive (
ts
) mutations in Semliki Forest virus (SFV) were previously identified within nsP1:
ts
10 (E529D) and
ts
14 (D119N). Recombinant viruses containing these individual mutations reproduced the features of the original
ts
strains. We now find that the capping-associated enzymatic activities of recombinant nsP1, containing
ts
10 or
ts
14 lesions, were not
ts
. The mutant proteins and polyproteins also were membrane bound, mutant nsP1 interacted normally with the other nonstructural proteins, and there was no major defect in nonstructural polyprotein processing in the mutants, although
ts
14 surprisingly displayed slightly retarded processing. The two mutant viruses were specifically defective in minus-strand RNA synthesis at the restrictive temperature. Integrating data from SFV and Sindbis virus, we discuss the domain structure of nsP1 and the relative positioning of and interactions between the replicase proteins. nsP1 is suggested to contain a specific subdomain involved in minus-strand synthesis and interaction with the polymerase nsP4 and the protease nsP2.
Comprehensive Characterization of Extracellular Herpes Simplex Virus Type 1 Virions
Authors: Loret Sandra , Guay Ginette , Lippé Roger 
Published: July 2008

ABSTRACT

The herpes simplex virus type 1 (HSV-1) genome is contained in a capsid wrapped by a complex tegument layer and an external envelope. The poorly defined tegument plays a critical role throughout the viral life cycle, including delivery of capsids to the nucleus, viral gene expression, capsid egress, and acquisition of the viral envelope. Current data suggest tegumentation is a dynamic and sequential process that starts in the nucleus and continues in the cytoplasm. Over two dozen proteins are assumed to be or are known to ultimately be added to virions as tegument, but its precise composition is currently unknown. Moreover, a comprehensive analysis of all proteins found in HSV-1 virions is still lacking. To better understand the implication of the tegument and host proteins incorporated into the virions, highly purified mature extracellular viruses were analyzed by mass spectrometry. The method proved accurate (95%) and sensitive and hinted at 8 different viral capsid proteins, 13 viral glycoproteins, and 23 potential viral teguments. Interestingly, four novel virion components were identified (U
L
7, U
L
23, U
L
50, and U
L
55), and two teguments were confirmed (ICP0 and ICP4). In contrast, U
L
4, U
L
24, the U
L
31/U
L
34 complex, and the viral U
L
15/U
L
28/U
L
33 terminase were undetected, as was most of the viral replication machinery, with the notable exception of U
L
23. Surprisingly, the viral glycoproteins gJ, gK, gN, and U
L
43 were absent. Analyses of virions produced by two unrelated cell lines suggest their protein compositions are largely cell type independent. Finally, but not least, up to 49 distinct host proteins were identified in the virions.
How can we improve estimates of bulk fault zone hydraulic properties?
Authors: Lunn Rebecca J. , Shipton Zoe K. , Bright Aileen M. 
Published: July 2008

Abstract

The fluid flow properties of faults are highly variable and spatially heterogeneous. We use numerical simulation of flow through field maps of detailed fault zone architecture to demonstrate that flow across the fault zone is controlled by connected high-permeability pathways, which are highly tortuous in mapped fault outcrops. Such small-scale, geometrically complex, fault zone architectural features can never be resolved for
subsurface
faults. Consequently, the key to prediction of subsurface bulk fault zone hydraulic properties is a statistical characterisation of the likelihood and frequency of such connected pathways. We demonstrate for a single architectural feature, the fault core, that thickness variation along strike can be well described by a spatially correlated random field with a spherical covariance structure. These data are from a single site in a specific lithology. To enable such statistics to be used to make predictions at other sites, a large number of similar datasets must be pooled. This will enable us to relate such spatial statistics to gross properties such as host rock lithology and fault throw, which are measurable for subsurface faults.
Fault-related dilation, permeability enhancement, fluid flow and mineral precipitation patterns: numerical models
Authors: Zhang Y. , Schaubs P. M. , Zhao C. , Ord A. , Hobbs B. E. , Barnicoat A. C. 
Published: July 2008

Abstract
Fault-related host rock deformation and dilation control fluid flow and mineralization in many world-class mineral deposits. This numerical modelling study explores the interactions between deformation, faulting, dilation, fluid flow and chemical processes, which are suggested to result in this control, with special attention to fault dilatant jog structures. Our two-dimensional numerical models focus on faulting-related deformation, dilation and permeability enhancement, fluid flow patterns and fluid focusing/mixing locations, while three-dimensional models examine several different cases of fault underlap and overlap. The results show that fault-dilation and faulting-induced permeability enhancement, which are closely associated with tensile failure, represent important ways to generate fluid flow conduits for more effective fluid flow and mixing. Dilation during strike–slip faulting is localized near fault tips (wing crack locations) and jog sites, where fluids are strongly focused and mixed. These locations are the tensile domains of the strike–slip regime. In overlapping-fault (dilatant jog) cases, the magnitude of dilation and the extent of the dilatant region are closely related to the extent of fault overlap. These results provide insight into the transport of fluids through low-permeability rocks with isolated, but more permeable, faults. Gold and quartz precipitation patterns as a result of the coupling of chemical reactions to deformation induced fluid flow velocities are also computed. The rates of precipitation depend on structural and fluid flow conditions and on the geometrical relation between local fluid velocity and chemical concentration gradients generated by mixing. Maximum precipitation rates for gold occur in the dilation zones and in faults where high fluid flow rates, sufficient fluid mixing and high concentration gradients of critical chemical species are all present, while the quartz precipitation rate is predominantly controlled, in this isothermal situation, by the rate of fluid flow across concentration gradients in the aqueous silica concentration.
Fault and fluid interaction in a rifted margin: integrated study of calcite-sealed fault-related structures (southern Corinth margin)
Authors: Benedicto A. , Plagnes V. , Vergély P. , Flotté N. , Schultz R. A. 
Published: July 2008

Abstract
This work integrates microstructural, petrologic, microthermometric and geochemical analysis of calcite-sealed fault-related structures of the major faults of the southern margin of the Corinth rift (Greece). It draws attention to the main deformational processes and fault–fluid interaction in fault zones along the whole margin. Data analysed come from the compact breccia located immediately adjacent to major fault planes. Samples were collected at different positions alongside different faults juxtaposing synrift continental deposits (hanging wall) against the prerift Pindus limestones (footwall). This implies hectometric fault displacements and that the fault zones have recorded a relatively long evolution of deformation. Our study identifies four main deformation features common to all studied faults: calcite cemented breccia, extensional veins, shear veins and fault slip surfaces. The integrated data analysis shows that deformation structures and fault rocks that coexist in the same outcrop formed at different depths and times. During inferred upward fault propagation, the style of deformation evolved from distributed (brecciation) to localized (slip surfaces) and from a closed system with fluid–rock equilibrium during brecciation to a more open one with limited influx of meteoric water during extensional and shear fracturing. This implies relative uplift of the footwall during fault propagation and fault interaction with different water aquifers as the fault propagates upwards. The results demonstrate similar fault evolution and fault–fluid interaction through the entire rifted margin and during the whole rifting period.
Permeability structure and co-seismic thermal pressurization on fault branches: insights from the Usukidani fault, Japan
Authors: Boutareaud Sebastien , Wibberley Christopher A. J. , Fabbri Olivier , Shimamoto Toshihiko 
Published: July 2008

Abstract
Detailed mapping of complex fault zones shows that secondary faults often branch off the principal slip zone. However, the effect of secondary branch faults on the hydrodynamic behaviour of fault zones has not yet been examined, largely because of a lack of hydraulic data and because numerical or analogue modelling of splay faulting is a complex issue. This contribution investigates the thermal pressurization process in cases of slip along a principal slip zone and along splay faults branching off the principal displacement zone. The study is based on porosity and permeability data presented in this paper from the principal and secondary slip zones of an active, clay-rich gouge-bearing strike–slip fault, the Usukidani fault of SW Japan. Modelling constrained by these data suggests that thermal pressurization is a viable process only as long as the rupture remains located in the central gouge zones or in mature splay fault gouge zones. Splaying of the rupture into surrounding microbreccias or into immature or newly generated splay faults of higher permeability will release fluid pressure or inhibit the generation of coseismic excess fluid pressures by thermal pressurization. The modelling results suggest that secondary fault branches can play a key role in controlling fluid pressurization during faulting. Hence, complete investigation of active fault zones needs to include secondary faults and their corresponding hydraulic behaviour, in order to establish the influence of such structures on earthquake mechanics.