Summary Background In an ongoing outbreak of haemolytic uraemic syndrome and bloody diarrhoea caused by a virulent Escherichia coli strain O104:H4 in Germany (with some cases elsewhere in Europe and ...North America), 810 cases of the syndrome and 39 deaths have occurred since the beginning of May, 2011. We analysed virulence profiles and relevant phenotypes of outbreak isolates recovered in our laboratory. Methods We analysed stool samples from 80 patients that had been submitted to the National Consulting Laboratory for Haemolytic Uraemic Syndrome in Münster, Germany, between May 23 and June 2, 2011. Isolates were screened with standard PCR for virulence genes of Shiga-toxin-producing E coli and a newly developed multiplex PCR for characteristic features of the outbreak strain ( rfbO104 , fliCH4 , stx2 , and terD ). Virulence profiles of the isolates were determined with PCR targeting typical virulence genes of Shiga-toxin-producing E coli and of other intestinal pathogenic E coli . We sequenced stx with Sanger sequencing and measured Shiga-toxin production, adherence to epithelial cells, and determined phylogeny and antimicrobial susceptibility. Findings All isolates were of the HUSEC041 clone (sequence type 678). All shared virulence profiles combining typical Shiga-toxin-producing E coli ( stx2 , iha, lpfO26 , lpfO113 ) and enteroaggregative E coli ( aggA, aggR, set1, pic, aap ) loci and expressed phenotypes that define Shiga-toxin-producing E coli and enteroaggregative E coli , including production of Shiga toxing 2 and aggregative adherence to epithelial cells. Isolates additionally displayed an extended-spectrum β-lactamase phenotype absent in HUSEC041. Interpretation Augmented adherence of the strain to intestinal epithelium might facilitate systemic absorption of Shiga toxin and could explain the high progression to haemolytic uraemic syndrome. This outbreak demonstrates that blended virulence profiles in enteric pathogens, introduced into susceptible populations, can have extreme consequences for infected people. Funding German Federal Ministry of Education and Research, Network Zoonoses.
Jingwenite-(Y), Y2Al2V24+(SiO4)O4(OH)4, the first V-HREE-bearing silicate mineral discovered in nature, is an abundant component of a sediment-hosted stratiform Cu (SSC) deposit in Yushui, South ...China. The mineral occurs in bedded/massive sulfide-bearing ore and is associated with bornite, chalcopyrite, galena, xenotime-(Y), nolanite, thortveitite, roscoelite, barite, and quartz. Optically, jingwenite-(Y) is biaxial (+), with α = 1.92(4), β = 1.95(2), γ = 1.99(3) (white light), and 2V (calculated) = 83°. The dispersion is medium with r < v, and the pleochroism is with X = light brown, Y = brown, Z = dark brown. The color, streak, luster, and hardness (Mohs) are light brown, yellowish gray, vitreous, and 4 1/2-5, respectively. Jingwenite-(Y) is monoclinic, with space group I2/a, Z = 4, and unit-cell parameters a = 9.4821(2) Å, b = 5.8781(1) Å, c = 19.3987(4) Å, β = 90.165(2)°, and V = 1081.21(4) Å3. The structure of jingwenite-(Y) has chains of edge-sharing Al(V,Fe)-O octahedra and V(Ti)-O octahedra extending along the b-axis and linked by insular Si-O tetrahedra, leaving open channels occupied by HREEs. Jingwenite-(Y) is a new nesosilicate structural type. Sm-Nd dating and Nd isotope signatures of jingwenite-(Y) reveal an epigenetic origin and suggest that HREEs and V were added to the SSC system via leaching of abundant heavy minerals in the footwall red sandstone by oxidized basinal brines. The abundance of jingwenite-(Y) at Yushui indicates that it could potentially be a valuable resource for HREE and V. Moreover, HREE and V mineralization can also occur in the same sediment-hosted Cu mineral system.
•In situ Raman spectra of tungstate-bearing solutions were collected at ≤400°C and ≤60Mpa.•CO32- and HCO3- do not associate with tungstate to form carbonic tungstate species.•Polymeric tungstate ...species are stable in CO2-bearing fluids at <300°C.•Monomeric tungstate species are responsible for hydrothermal transport of W at >300°C.•The presence of CO2 favors the extraction of Fe(II) from the host rock and subsequent W-mineralization.
Knowledge on hydrothermal tungsten (W) species is vital towards a better understanding of tungsten transport and mineralization mechanisms. In this study, in situ Raman spectra of a 0.005 – 0.1mol/kg (m) K2WO4 solution containing CO2, HCl, and NaHCO3 were collected at 50–400°C and 20–60MPa. The spectra for the symmetric stretching vibration mode of the WO bond, v1(WO), were analyzed to investigate the hydrothermal tungstate species. Results showed that carbonate/bicarbonate do not associate with tungstate to form carbonic tungstate species. Nevertheless, the presence of CO2 can increase the fluid acidity, which favors the formation of polymeric tungstate species at <300°C. Above about 300°C, monomeric tungstates (e.g., WO42-, HWO4-, H2WO4 and alkali tungstate ion pairs) are responsible for the hydrothermal transport of tungsten, and the v1(WO) modes of these species are centered at ∼930 cm-1 and 950cm-1. Based on the above observations, we simulated the mineralization process in the context of fluid-rock interactions using tungstate and alkali tungstate ion pairs as the only aqueous W species. The thermodynamic simulations showed that (a) the timing of mineralization mainly depends on the W concentration in the initial mineralizing fluid and the availability of Ca2+, Fe2+ and Mn2+, with higher W concentrations generally favoring higher temperature mineralization; (b) highly W-enriched fluid is not essential for W mineralization, while extremely low contents of Fe, Mn and Ca in the magma are useful to maintain the mobility of aqueous W until favorable host rocks are encountered; and (c) a “hydrogen reservoir” effect was identified for dissolved CO2. The presence of CO2 can promote the extraction of Fe(II) from the pelitic host rocks, thereby facilitating a high-grade vein-type W mineralization.
At <∼300°C, polytungstate species, whose v1(WO) modes are centered at ∼965 – 995 cm-1, are important hydrothermal W species along with monomeric tungstates. Therefore, polymeric tungstate species should be considered in future thermodynamic modeling of W transport and mineralization at <300°C. An increase in fluid pH induced by CO2-escape and/or fluid-rock interactions will destabilize the polymeric tungstates to form WO42- and other monomeric tungstate, which interacts with metal cations to form wolframite and/or scheelite.
Outer membrane vesicles (OMVs) are important tools in bacterial virulence but their role in the pathogenesis of infections caused by enterohemorrhagic Escherichia coli (EHEC) O157, the leading cause ...of life-threatening hemolytic uremic syndrome, is poorly understood. Using proteomics, electron and confocal laser scanning microscopy, immunoblotting, and bioassays, we investigated OMVs secreted by EHEC O157 clinical isolates for virulence factors cargoes, interactions with pathogenetically relevant human cells, and mechanisms of cell injury. We demonstrate that O157 OMVs carry a cocktail of key virulence factors of EHEC O157 including Shiga toxin 2a (Stx2a), cytolethal distending toxin V (CdtV), EHEC hemolysin, and flagellin. The toxins are internalized by cells via dynamin-dependent endocytosis of OMVs and differentially separate from vesicles during intracellular trafficking. Stx2a and CdtV-B, the DNase-like CdtV subunit, separate from OMVs in early endosomes. Stx2a is trafficked, in association with its receptor globotriaosylceramide within detergent-resistant membranes, to the Golgi complex and the endoplasmic reticulum from where the catalytic Stx2a A1 fragment is translocated to the cytosol. CdtV-B is, after its retrograde transport to the endoplasmic reticulum, translocated to the nucleus to reach DNA. CdtV-A and CdtV-C subunits remain OMV-associated and are sorted with OMVs to lysosomes. EHEC hemolysin separates from OMVs in lysosomes and targets mitochondria. The OMV-delivered CdtV-B causes cellular DNA damage, which activates DNA damage responses leading to G2 cell cycle arrest. The arrested cells ultimately die of apoptosis induced by Stx2a and CdtV via caspase-9 activation. By demonstrating that naturally secreted EHEC O157 OMVs carry and deliver into cells a cocktail of biologically active virulence factors, thereby causing cell death, and by performing first comprehensive analysis of intracellular trafficking of OMVs and OMV-delivered virulence factors, we provide new insights into the pathogenesis of EHEC O157 infections. Our data have implications for considering O157 OMVs as vaccine candidates.
An ongoing outbreak of exceptionally virulent Shiga toxin (Stx)-producing Escherichia coli O104:H4 centered in Germany, has caused over 830 cases of hemolytic uremic syndrome (HUS) and 46 deaths ...since May 2011. Serotype O104:H4, which has not been detected in animals, has rarely been associated with HUS in the past. To prospectively elucidate the unique characteristics of this strain in the early stages of this outbreak, we applied whole genome sequencing on the Life Technologies Ion Torrent PGM™ sequencer and Optical Mapping to characterize one outbreak isolate (LB226692) and a historic O104:H4 HUS isolate from 2001 (01-09591). Reference guided draft assemblies of both strains were completed with the newly introduced PGM™ within 62 hours. The HUS-associated strains both carried genes typically found in two types of pathogenic E. coli, enteroaggregative E. coli (EAEC) and enterohemorrhagic E. coli (EHEC). Phylogenetic analyses of 1,144 core E. coli genes indicate that the HUS-causing O104:H4 strains and the previously published sequence of the EAEC strain 55989 show a close relationship but are only distantly related to common EHEC serotypes. Though closely related, the outbreak strain differs from the 2001 strain in plasmid content and fimbrial genes. We propose a model in which EAEC 55989 and EHEC O104:H4 strains evolved from a common EHEC O104:H4 progenitor, and suggest that by stepwise gain and loss of chromosomal and plasmid-encoded virulence factors, a highly pathogenic hybrid of EAEC and EHEC emerged as the current outbreak clone. In conclusion, rapid next-generation technologies facilitated prospective whole genome characterization in the early stages of an outbreak.
Background
The studies of science, technology, engineering, and mathematics (STEM) career interests have progressed substantially over the recent years. However, the influence of career awareness on ...STEM career interests is an area that requires further discussion. Evidently, Chinese adolescents have limited awareness and interest in STEM careers in the context of the Chinese cultural milieu, which can potentially constrain their future career trajectories. This study explored the influence of career awareness on the STEM career interests of Chinese high school students, examining the mediating roles of self-efficacy and outcome expectations for STEM courses in this relationship. Additionally, it analyzes the impact of gender on the average levels and interrelations of these variables. A sample of high school students from both eastern and western regions of China (
N
= 2542) was selected, and data was analyzed using a structural equation modeling approach.
Results
The findings indicate that while STEM career awareness impacts various types of STEM career interests, minor differences exist in these effects. Specifically, the influence of STEM career awareness on analytical STEM career interests is entirely mediated by self-efficacy and outcome expectations in STEM courses. However, for life-survival and life-healthy STEM career interests, this mediation is only partial, with respective effects accounting for 39% and 45%. Notably, significant mean-level differences exist between male and female students in STEM career interests and self-efficacy in STEM courses, yet the relationships among these variables remain consistent across genders.
Conclusions
This study underscores the pivotal influence of career awareness in molding STEM career interests, shedding light on the mediating functions of self-efficacy and outcome expectations within STEM courses. Through a gender-based analysis, it offers valuable insights into the differing inclinations of male and female high school students in the STEM realm, while also revealing consistent patterns in the relationships among these variables across genders. These findings underscore the necessity for heightened efforts to bolster STEM career awareness and fortify self-efficacy and outcome expectations within STEM courses, particularly in domains characterized by notable gender disparities, aiming to foster equitable advancement within the STEM disciplines.
Enterohemorrhagic Escherichia coli (EHEC) strains cause diarrhea and hemolytic uremic syndrome resulting from toxin-mediated microvascular endothelial injury. EHEC hemolysin (EHEC-Hly), a member of ...the RTX (repeats-in-toxin) family, is an EHEC virulence factor of increasingly recognized importance. The toxin exists as free EHEC-Hly and as EHEC-Hly associated with outer membrane vesicles (OMVs) released by EHEC during growth. Whereas the free toxin is lytic towards human endothelium, the biological effects of the OMV-associated EHEC-Hly on microvascular endothelial and intestinal epithelial cells, which are the major targets during EHEC infection, are unknown. Using microscopic, biochemical, flow cytometry and functional analyses of human brain microvascular endothelial cells (HBMEC) and Caco-2 cells we demonstrate that OMV-associated EHEC-Hly does not lyse the target cells but triggers their apoptosis. The OMV-associated toxin is internalized by HBMEC and Caco-2 cells via dynamin-dependent endocytosis of OMVs and trafficked with OMVs into endo-lysosomal compartments. Upon endosome acidification and subsequent pH drop, EHEC-Hly is separated from OMVs, escapes from the lysosomes, most probably via its pore-forming activity, and targets mitochondria. This results in decrease of the mitochondrial transmembrane potential and translocation of cytochrome c to the cytosol, indicating EHEC-Hly-mediated permeabilization of the mitochondrial membranes. Subsequent activation of caspase-9 and caspase-3 leads to apoptotic cell death as evidenced by DNA fragmentation and chromatin condensation in the intoxicated cells. The ability of OMV-associated EHEC-Hly to trigger the mitochondrial apoptotic pathway in human microvascular endothelial and intestinal epithelial cells indicates a novel mechanism of EHEC-Hly involvement in the pathogenesis of EHEC diseases. The OMV-mediated intracellular delivery represents a newly recognized mechanism for a bacterial toxin to enter host cells in order to target mitochondria.
In this work, the 〈100〉 directional solidified feedstock slabs were used to produce the rolled Fe–Ga sheets, and sharp Goss orientation was developed in the 0.3mm sheets after annealing processes. ...The area fraction of Goss grains in the annealed binary Fe–Ga sheets approached to 62.4% without abnormal grain growth, accompanied with a maximum magnetostriction (λ//−λ⊥) of 199ppm. The addition of only 0.1at% NbC notably promoted the abnormal Goss grain growth without sulfur annealing, and large single-crystal-like grains, up to several centimeters, were obtained with few island-like grains after sulfur annealing and final Ar/H2 annealing processes. High magnetostriction (λ//−λ⊥) of 245ppm with little deviation was achieved in the (Fe83Ga17)99.9(NbC)0.1 sheets, and a large magnetostrictive strain (λ//) up to 243ppm under no pre-stress was observed with an applied magnetic field along the rolling direction.
•The 〈100〉 oriented feedstock slabs were used to prepare Goss oriented Fe–Ga sheets.•Abnormal Goss grain growth was observed in the 0.3mm sheets with only 0.1at% NbC.•A high λ// of 243ppm under no pre-stress was observed along the RD.
A genomic island encoding the biosynthesis and secretion pathway of putative hybrid nonribosomal peptide-polyketide colibactin has been recently described in Escherichia coli. Colibactin acts as a ...cyclomodulin and blocks the eukaryotic cell cycle. The origin and prevalence of the colibactin island among enterobacteria are unknown. We therefore screened 1,565 isolates of different genera and species related to the Enterobacteriaceae by PCR for the presence of this DNA element. The island was detected not only in E. coli but also in Klebsiella pneumoniae, Enterobacter aerogenes, and Citrobacter koseri isolates. It was highly conserved among these species and was always associated with the yersiniabactin determinant. Structural variations between individual strains were only observed in an intergenic region containing variable numbers of tandem repeats. In E. coli, the colibactin island was usually restricted to isolates of phylogenetic group B2 and inserted at the asnW tRNA locus. Interestingly, in K. pneumoniae, E. aerogenes, C. koseri, and three E. coli strains of phylogenetic group B1, the functional colibactin determinant was associated with a genetic element similar to the integrative and conjugative elements ICEEc1 and ICEKp1 and to several enterobacterial plasmids. Different asn tRNA genes served as chromosomal insertion sites of the ICE-associated colibactin determinant: asnU in the three E. coli strains of ECOR group B1, and different asn tRNA loci in K. pneumoniae. The detection of the colibactin genes associated with an ICE-like element in several enterobacteria provides new insights into the spread of this gene cluster and its putative mode of transfer. Our results shed light on the mechanisms of genetic exchange between members of the family ENTEROBACTERIACEAE:
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