Proteome profiling by label‐free mass spectrometry reveals differentiated response of Campylobacter jejuni 81–176 to sublethal concentrations of bile acids.

Purpose Bile acids are crucial components of the intestinal antimicrobial defense and represent a significant stress factor for enteric pathogens. Adaptation processes of Campylobacter jejuni to this hostile environment are analyzed in this study by a proteomic approach. Experimental design Proteome profiling by label-free mass spectrometry (SWATH-MS) has been used to characterize the adaptation of C. jejuni to sublethal concentrations of seven bile acids. Results The bile acids with the lowest inhibitory concentration (IC50), deoxycholic and chenodeoxycholic acid, induce the most significant proteome changes. Overall a downregulation of all basic biosynthetic pathways and a general decrease in the transcription machinery are found. Concurrently, an induction of factors involved in detoxification of reactive oxygen species, protein folding, and bile acid exporting efflux pumps is detected. Exposure to deoxycholic and chenodeoxycholic acid results in an increased expression of components of the more energy-efficient aerobic respiration pathway, while the anaerobic branches of the electron transport chain are down-expressed. Conclusions and clinical relevance The results show that C. jejuni has a differentiated system of adaptation to bile acid stresses. The findings enhance the understanding of the pathogenesis of campylobacteriosis, especially for survival of C. jejuni in the human intestine, and may provide clues to future medical treatment

Characterization of Human Endogenous Retrovirus Type K Virus-like Particles Generated from Recombinant Baculoviruses

AbstractThe family of human endogenous retrovirus type K (HERV-K) comprises members with long open reading frames (ORF) for retroviral proteins. The existence of a biologically active provirus with replicative capacities has not yet been demonstrated. To confirm the assumption that HERV-K codes for the previously observed retrovirus-like particles (human teratocarcinoma-derived virus, HTDV) in human teratocarcinoma cells, we have constructed recombinant full-length HERV-K cDNA-based baculoviruses withgag, pro, pol,andenvORFs. Two viral constructs were used for infections of insect cells, one bearing 67 bp of the 5′ untranslated region upstream of the 5′ splice donor (SD) site and of the retroviral genes, the second omitting the SD sequence. For both recombinant viruses, indirect immunofluorescence and laser scan analyses revealed expression of HERV-K Gag protein. Electron microscopy studies demonstrated efficient production of virus-like particles (VLPs) at the cytoplasmic cell membranes. These VLPs are morphologically identical with the HTDV phenotype. In immunoelectron microscopy of ultrathin frozen sections, anti-HERV-K Gag antibodies specifically reacted with HERV-K VLPs. In Western blots, in addition to the 76-kDa precursor protein, the putative major core protein with an apparent molecular mass of 32 kDa exhibited predominant immunoreactivity with anti-Gag antiserum. In contrast, neither HERV-K Env nor cORF proteins could be detected due to inefficient mRNA splicing. Purified particles from insect cell culture supernatants tested in an ultrasensitive reverse transcriptase assay revealed weak polymerase activity. The data demonstrate that HERV-K codes for retroviral particles of the HTDV phenotype

Measurement of the Beam Asymmetry Σ\Sigma in the Forward Direction for pi0 Photoproduction

Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector for photon energies between 0.92 and 1.68~GeV at the electron accelerator ELSA. The beam asymmetry~$\Sigma$ has been extracted for $115^\circ < \theta_{\rm c.m.} < 155^\circ$ of the $\pi^0$~meson and for $\theta_{\rm c.m.} < 60^\circ$. The new beam asymmetry data improve the world database for photon energies above 1.5~GeV and, by covering the very forward region, extend previously published data for the same reaction by our collaboration. The angular dependence of $\Sigma$ shows overall good agreement with the SAID parameterization.Comment: 11 pages, 10 figures, published in Phys. Rev. C, included LEPS data and MAID 2007 predictions for comparison with our dat

Neutron skin of 208^{208}Pb from Coherent Pion Photoproduction

Information on the size and shape of the neutron skin on $^{208}$Pb has been extracted from coherent pion photoproduction cross sections measured using the Crystal Ball together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections the half-height radius and diffuseness of the neutron distribution are found to be 6.70$\pm 0.03(stat)$ fm and 0.55$\pm 0.01(stat)$$^{+0.02}_{-0.03}(sys)$ fm respectively, corresponding to a neutron skin thickness $\Delta r_{np}$=0.15$\pm 0.03(stat)$$^{+0.01}_{-0.03}(sys)$ fm. The results give the first successful extraction of a neutron skin with an electromagnetic probe and indicate the skin of $^{208}$Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.Comment: 4 figures 5 pages. Version submitted to journal. Includes additional studies of systematic effects in the extracted diffuseness, which led to a small increase in the quoted systematic error. These additional studies are discussed in the revised manuscript. Also includes minor editorial improvements to the tex

Photoproduction of Neutral Pions off Protons

Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction $\gamma p\to p\pi^0$ for photon energies between 0.85 and 2.50 GeV. The $\pi^0$ mesons are observed in their dominant neutral decay mode: $\pi^0\to\gamma\gamma$. For the first time, the differential cross sections cover the very forward region, $\theta_{\rm c.m.}<60^\circ$. A partial-wave analysis of these data within the Bonn-Gatchina framework observes the high-mass resonances $G_{17}$(2190), $D_{13}$(2080), and $D_{15}$(2070).Comment: 12 pages, 9 figures, minor modifications to PWA sectio

Modification of the ω\omega-Meson Lifetime in Nuclear Matter

The photo production of $\omega$ mesons on the nuclei C, Ca, Nb and Pb has been measured using the Crystal Barrel/TAPS detector at the ELSA tagged photon facility in Bonn. The dependence of the $\omega$ meson cross section on the nuclear mass number has been compared with three different types of models, a Glauber analysis, a BUU analysis of the Giessen theory group and a calculation by the Valencia theory group. In all three cases, the inelastic $\omega$ width is found to be $130-150 \rm{MeV/c^2}$ at normal nuclear matter density for an average 3-momentum of 1.1 GeV/c. In the restframe of the $\omega$ meson, this inelastic $\omega$ width corresponds to a reduction of the $\omega$ lifetime by a factor $\approx 30$. For the first time, the momentum dependent $\omega$N cross section has been extracted from the experiment and is in the range of 70 mb.Comment: 5 pages, 4 figure

Determination of the Dalitz plot parameter alpha for the decay eta->3pi^0 with the Crystal Ball at MAMI-B

A precise measurement of the Dalitz plot parameter, alpha, for the eta->3pi^0 decay is presented. The experiment was performed with the Crystal Ball and TAPS large acceptance photon detectors at the tagged photon beam facility of the MAMI-B electron accelerator in Mainz. High statistics of 1.8*10^6 eta->3pi^0 events were obtained, giving the result alpha = -0.032 +/- 0.002(stat) +/- 0.002(syst).Comment: 9 pages, 6 figures, published in the online-first section of EPJ A, included changes referees asked for, added DO

Photoproduction of meson pairs: First measurement of the polarization observable I^s

The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Fits using Bonn-Gatchina partial wave analysis demonstrate that the new polarization observables carry significant information on the contributing partial waves.Comment: 11 pages, 6 figures, v2 to appear in Phys. Lett.

Photoproduction of {\omega} Mesons off the Proton

The differential cross sections and unpolarized spin-density matrix elements for the reaction $\gamma p\to p\omega$ were measured using the CBELSA/TAPS experiment for initial photon energies ranging from the reaction threshold to 2.5 GeV. These observables were measured from the radiative decay of the $\omega$ meson, $\omega\to\pi^0\gamma$. The cross sections cover the full angular range and show the full extent of the $t$-channel forward rise. The overall shape of the angular distributions in the differential cross sections and unpolarized spin-density matrix elements are in fair agreement with previous data. In addition, for the first time, a beam of linearly-polarized tagged photons in the energy range from 1150 MeV to 1650 MeV was used to extract polarized spin-density matrix elements. These data were included in the Bonn-Gatchina partial wave analysis (PWA). The dominant contribution to $\omega$ photoproduction near threshold was found to be the $3/2^+$ partial wave, which is primarily due to the sub-threshold $N(1720)\,3/2^+$ resonance. At higher energies, pomeron-exchange was found to dominate whereas $\pi$-exchange remained small. These $t$-channel contributions as well as further contributions from nucleon resonances were necessary to describe the entire dataset: the $1/2^-$, $3/2^-$, and $5/2^+$ partial waves were also found to contribute significantly.Comment: 8 pages, 5 figures, accepted for publication in Physics Letters

High statistics study of the reaction γp→p 2π0\gamma p\to p\;2\pi^0

The photoproduction of 2$\pi^0$ mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged in the energy range from 600\,MeV to 2.5\,GeV. Differential and total cross sections and $p\pi^0\pi^0$ Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and $\Delta$ resonances contributing to the $p\pi^0\pi^0$ final state were determined within the BnGa partial wave analysis. The data presented here allow us to determine branching ratios of nucleon and $\Delta$ resonances for their decays into $p\pi^0\pi^0$ via several intermediate states. Most prominent are decays proceeding via $\Delta(1232)\pi$, $N(1440)1/2^+\pi$, $N(1520)3/2^-\pi$, $N(1680)5/2^+\pi$, but also $pf_0(500)$, $pf_0(980)$, and $pf_2(1270)$ contribute to the reaction.Comment: 28 pages, 17 figures, 7 table