The cytochrome bd-I respiratory oxidase augments survival of multidrug-resistant Escherichia coli during infection

Nitric oxide (NO) is a toxic free radical produced by neutrophils and macrophages in response to infection. Uropathogenic Escherichia coli (UPEC) induces a variety of defence mechanisms in response to NO, including direct NO detoxification (Hmp, NorVW, NrfA), iron-sulphur cluster repair (YtfE), and the expression of the NO-tolerant cytochrome bd-I respiratory oxidase (CydAB). The current study quantifies the relative contribution of these systems to UPEC growth and survival during infection. Loss of the flavohemoglobin Hmp and cytochrome bd-I elicit the greatest sensitivity to NO-mediated growth inhibition, whereas all but the periplasmic nitrite reductase NrfA provide protection against neutrophil killing and promote survival within activated macrophages. Intriguingly, the cytochrome bd-I respiratory oxidase was the only system that augmented UPEC survival in a mouse model after 2 days, suggesting that maintaining aerobic respiration under conditions of nitrosative stress is a key factor for host colonisation. These findings suggest that while UPEC have acquired a host of specialized mechanisms to evade nitrosative stresses, the cytochrome bd-I respiratory oxidase is the main contributor to NO tolerance and host colonisation under microaerobic conditions. This respiratory complex is therefore of major importance for the accumulation of high bacterial loads during infection of the urinary tract

Mulit-Photon Events with Large Missing energy in e+e- collisions at sqrt(s)=192-209 GeV

Events with a final state consisting of two or more photons and large missing transverse energy have been observed in e+e- collisions at centre-of-mass energies in the range 192 - 209 GeV using the OPAL detector at LEP. Cross-section measurements are performed within the kinematic acceptance of the selection and compared with the expectation from the Standard Model process e+e- -> nu nu gamma gamma(gamma). No evidence for new physics contributions to this final state is observed. Upper limits on sigma (e+e- -> XX) BR^2(X -> Ygamma) are derived for the case of stable and invisible Y. In the case of massive Y the combined limits obtained from all the data range from 10 fb to 60 fb, while for the special case of massless Y the range is 20 fb to 40 fb. The limits apply to pair production of excited neutrions (X=nu^*,Y=nu), to neutralino production (X=~chi^0_2, Y=~chi^0_1) and to supersymmetric models in which X=~chi^0_1 and Y=~G is a light gravitino.Comment: 18 pages, 4 figures, Submitted to Phys. Letts

Search for Associated Production of Massive States Decaying into Two Photonsin e+e- Annihilations at sqrt(s) = 88-209 GeV

A search is performed for production of short-lived particles in e+e- -> XY, with X -> gamma gamma and Y -> ffbar, for scalar X and scalar or vector Y. Model-independent limits in the range of 25-60 femtobarns are presented on sigma (e+e- -> XY) x B(X -> ffbar) for centre-of-mass energies in the range 205-207 GeV. The data from all LEP centre-of-mass energies 88-209 GeV are also interpreted in the context of fermiophobic Higgs boson models, for which a lower mass limit of 105.5 GeV is obtained for a "benchmark" fermiophobic Higgs boson.Comment: 17 pages, 4 figure

Salmonella employs multiple mechanisms to subvert the TLR-inducible zinc-mediated antimicrobial response of human macrophages

© FASEB. We aimed to characterize antimicrobial zinc trafficking within macrophages and to determine whether the professional intramacrophage pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) subverts this pathway. Using both Escherichia coli and S. Typhimurium, we show that TLR signaling promotes the accumulation of vesicular zinc within primary human macrophages. Vesicular zinc is delivered to E. coli to promote microbial clearance, whereas S. Typhimurium evades this response via Salmonella pathogenicity island (SPI)-1. Even in the absence of SPI-1 and the zinc exporter ZntA, S. Typhimurium resists the innate immune zinc stress response, implying the existence of additional host subversion mechanisms. We also demonstrate the combinatorial antimicrobial effects of zinc and copper, a pathway that S. Typhimurium again evades. Our use of complementary tools and approaches, including confocal microscopy, direct assessment of intramacrophage bacterial zinc stress responses, specific E. coli and S. Typhimurium mutants, and inductively coupled plasma mass spectroscopy, has enabled carefully controlled characterization of this novel innate immune antimicrobial pathway. In summary, our study provides new insights at the cellular level into the well-documented effects of zinc in promoting host defense against infectious disease, as well as the complex host subversion strategies employed by S. Typhimurium to combat this pathway

Constraints on anomalous quartic gauge boson couplings from nu(nu)over-bar gamma gamma and q(q)over-bar gamma gamma events at CERN LEP2

Anomalous quartic couplings between the electroweak gauge bosons may contribute to the nu(nu) over bar gammagamma and q (q) over bar gammagamma final states produced in e(+)e(-) collisions. This analysis uses the LEP2 OPAL data sample at center-of-mass energies up to 209 GeV. Event selections identify nu(nu) over bar gammagamma and q (q) over bar gammagamma events in which the two photons are reconstructed within the detector acceptance. The cross section for the process e(+)e(-)-->q (q) over bar gammagamma is measured. Averaging over all energies, the ratio of the observed e(+)e(-)-->q (q) over bar gammagamma cross section to the standard model expectation is R(data/SM)=0.92+/-0.07+/-0.04, where the errors represent the statistical and systematic uncertainties respectively. The nu(nu) over bar gammagamma and q (q) over bar gammagamma data are used to constrain possible anomalous W(+)W(-)gammagamma and ZZgammagamma couplings. Combining with previous OPAL results from the W(+)W(-)gamma final state, the 95% confidence level limits on the anomalous coupling parameters a(0)(Z), a(c)(Z), a(0)(W) and a(c)(W) are found to be -0.007 GeV-2<a(0)(Z)/Lambda(2)<0.023 GeV-2, -0.029 GeV-2<a(c)(Z)/Lambda(2)<0.029 GeV-2, -0.020 GeV-2<a(0)(W)/Lambda(2)<0.020 GeV-2, -0.052 GeV-2<a(c)(W)/Lambda(2)<0.037 GeV-2, where Lambda is the energy scale of the new physics. Limits found when allowing two or more parameters to vary are also presented

Bose-Einstein study of position-momentum correlations of charged pions in hadronic Z0 decays

A study of Bose-Einstein correlations in pairs of identically charged pions produced in e+e- annihilations at the Z0 peak has been performed for the first time assuming a non-static emitting source. The results are based on the high statistics data obtained with the OPAL detector at LEP. The correlation functions have been analyzed in intervals of the average pair transverse momentum and of the pair rapidity, in order to study possible correlations between the pion production points and their momenta (position-momentum correlations). The Yano-Koonin and the Bertsch-Pratt parameterizations have been fitted to the measured correlation functions to estimate the geometrical parameters of the source as well as the velocity of the source elements with respect to the overall centre-of-mass frame. The source rapidity is found to scale approximately with the pair rapidity, and both the longitudinal and transverse source dimensions are found to decrease for increasing average pair transverse momenta.Comment: 25 pages, 10 figures, Submitted to Eur Phys J.

Inclusive production of charged hadrons in photon-photon collisions

The inclusive production of charged hadrons in the collisions of quasi-real photons e+e- -> e+e- +X has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass energies from 183 to 209 GeV. The differential cross-sections as a function of the transverse momentum and the pseudorapidity of the hadrons are compared to theoretical calculations of up to next-to-leading order (NLO) in the strong coupling constant alpha{s}. The data are also compared to a measurement by the L3 Collaboration, in which a large deviation from the NLO predictions is observed.Comment: 20 pages, 4 figures, Submitted to Phys. Letts.

A study of W+W-gamma events at LEP

A study of W+W- events accompanied by hard photon radiation, Egamma > 2.5 GeV, produced in e(+)e(-) collisions at LEP is presented. Events consistent with being two on-shell W-bosons and an isolated photon are selected from 681 pb(-1) of data recorded at 180 GeV < roots < 209 GeV. From the sample of 187 selected W(+)W(-)gamma candidates with photon energies greater than 2.5 GeV, the W(+)W(-)gamma cross-section is determined at five values of roots. The results are consistent with the Standard Model expectation. Averaging over all energies, the ratio of the observed cross-section to the Standard Model expectation is R(data/SM) = 0.99 +/- 0.09 +/- 0.04, where the errors represent the statistical and systematic uncertainties respectively. These data provide constraints on the related O(alpha) systematic uncertainties on the measurement of the W-boson mass at LEP. Finally, the data are used to derive 95% confidence level upper limits on possible anomalous contributions to the W(+)W(-)gammagamma and W(+)W(-)Z(0)y vertices: -0.020 GeV-2 < a(0)/Lambda(2) < 0.020 GeV-2, -0.053 GeV-2 < a(c)/Lambda(2) < 0.037 GeV-2, -0.16 GeV-2 < a(n)/Lambda(2) < 0.15 GeV-2, where Lambda represents the energy scale for new physics and a(0), a(c) and a(n) are dimensionless coupling constants. (C) 2003 Elsevier B.V. All rights reserved