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81.
Jürgen Voigt Dieter Mergenhagen Petra Münzner Hans-Peter Vogeler Klaus Nagel 《Planta》1989,178(4):456-462
In light-dark-synchronized cultures of the unicellular green algaChlamydomonas reinhardtii, release of zoospores from the wall of the mother cell normally takes place during the second half of the dark period. The recently isolated mutant ls, however, needs light for the liberation of zoospores when grown photoautotrophically under a 12 h light-12 h dark regime. The light-induced release of zoospores was found to be prevented by addition of the photosystem-II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Furthermore, light dependence of this process was shown to be abolished when the mutant ls was grown either photoautotrophically under a 14 h light-10 h dark regime or in the presence of acetate. Our findings indicate that the light-dependency of zoospore liberation observed in cultures of this particular mutant during photoautotrophic growth under a 12 h light-12 h dark regime might be attributed to an altered energy metabolism. The light-induced release of zoospores was found to be prevented by addition of cycloheximide or chloramphenicol, antibiotics which inhibit protein biosynthesis by cytoplasmic and organellar ribosomes, respectively. Actinomycin D, an inhibitor of RNA synthesis, however, did not affect the light-induced liberation of zoospores.Sporangia accumulate in stationary cultures of the mutant ls. Release of zoospores was observed when these sporangia were collected by centrifugation and incubated in the light after resuspension in fresh culture medium. Since liberation of zoospores was not observed after dilution of the stationary cultures with fresh culture medium, we suppose that components which interfere with the action of the sporangial autolysin are accumulated in the culture medium of the mutant ls.Abbreviation DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea 相似文献
82.
The aim of this work was to describe the temperature dependence of microbial inactivation for several storage conditions and protective systems (lactose, trehalose and dextran) in relation to the physical state of the sample, i.e. the glassy or non-glassy state. The resulting inactivation rates k were described by applying two models, Arrhenius and Williams–Landel–Ferry (WLF), in order to evaluate the relevance of diffusional limitation as a protective mechanism. The application of the Arrhenius model revealed a significant decrease in activation energy Ea for storage conditions close to Tg. This finding is an indication that the protective effect of a surrounding glassy matrix can, at least, partly be ascribed to its inherent restricted diffusion and mobility. The application of the WLF model revealed that the temperature dependence of microbial inactivation above Tg is significantly weaker than predicted by the universal coefficients. Thus, it can be concluded that microbial inactivation is not directly linked with the mechanical relaxation behavior of the surrounding matrix as it was reported for viscosity and crystallization phenomena in case of disaccharide systems. 相似文献
83.
Apirat Chaikuad Ivan Alfano Georgina Kerr Caroline E. Sanvitale Jan H. Boergermann James T. Triffitt Frank von Delft Stefan Knapp Petra Knaus Alex N. Bullock 《The Journal of biological chemistry》2012,287(44):36990-36998
Bone morphogenetic protein (BMP) receptor kinases are tightly regulated to control development and tissue homeostasis. Mutant receptor kinase domains escape regulation leading to severely degenerative diseases and represent an important therapeutic target. Fibrodysplasia ossificans progressiva (FOP) is a rare but devastating disorder of extraskeletal bone formation. FOP-associated mutations in the BMP receptor ALK2 reduce binding of the inhibitor FKBP12 and promote leaky signaling in the absence of ligand. To establish structural mechanisms of receptor regulation and to address the effects of FOP mutation, we determined the crystal structure of the cytoplasmic domain of ALK2 in complex with the inhibitors FKBP12 and dorsomorphin. FOP mutations break critical interactions that stabilize the inactive state of the kinase, thereby facilitating structural rearrangements that diminish FKBP12 binding and promote the correct positioning of the glycine-serine-rich loop and αC helix for kinase activation. The balance of these effects accounts for the comparable activity of R206H and L196P. Kinase activation in the clinically benign mutant L196P is far weaker than R206H but yields equivalent signals due to the stronger interaction of FKBP12 with R206H. The presented ALK2 structure offers a valuable template for the further design of specific inhibitors of BMP signaling. 相似文献
84.
María Balseiro-Romero Petra S. Kidd Carmela Monterroso 《International journal of phytoremediation》2014,16(7-8):824-839
Vegetation and its associated microorganisms play an important role in the behaviour of soil contaminants. One of the most important elements is root exudation, since it can affect the mobility, and therefore, the bioavailability of soil contaminants. In this study, we evaluated the influence of root exudates on the mobility of fuel derived compounds in contaminated soils. Samples of humic acid, montmorillonite, and an A horizon from an alumi-umbric Cambisol were contaminated with volatile contaminants present in fuel: oxygenates (MTBE and ETBE) and monoaromatic compounds (benzene, toluene, ethylbenzene and xylene). Natural root exudates obtained from Holcus lanatus and Cytisus striatus and ten artificial exudates (components frequently found in natural exudates) were added to the samples, individually and as a mixture, to evaluate their effects on contaminant mobility. Fuel compounds were analyzed by headspace-gas chromatography-mass spectrometry. In general, the addition of natural and artificial exudates increased the mobility of all contaminants in humic acid. In A horizon and montmorillonite, natural or artificial exudates (as a mixture) decreased the contaminant mobility. However, artificial exudates individually had different effects: carboxylic components increased and phenolic components decreased the contaminant mobility. These results established a base for developing and improving phytoremediation processes of fuel-contaminated soils. 相似文献
85.
The complete genome sequence of Bacillus licheniformis DSM13, an organism with great industrial potential 总被引:8,自引:0,他引:8
Veith B Herzberg C Steckel S Feesche J Maurer KH Ehrenreich P Bäumer S Henne A Liesegang H Merkl R Ehrenreich A Gottschalk G 《Journal of molecular microbiology and biotechnology》2004,7(4):204-211
The genome of Bacillus licheniformis DSM13 consists of a single chromosome that has a size of 4,222,748 base pairs. The average G+C ratio is 46.2%. 4,286 open reading frames, 72 tRNA genes, 7 rRNA operons and 20 transposase genes were identified. The genome shows a marked co-linearity with Bacillus subtilis but contains defined inserted regions that can be identified at the sequence as well as at the functional level. B. licheniformis DSM13 has a well-conserved secretory system, no polyketide biosynthesis, but is able to form the lipopeptide lichenysin. From the further analysis of the genome sequence, we identified conserved regulatory DNA motives, the occurrence of the glyoxylate bypass and the presence of anaerobic ribonucleotide reductase explaining that B. licheniformis is able to grow on acetate and 2,3-butanediol as well as anaerobically on glucose. Many new genes of potential interest for biotechnological applications were found in B. licheniformis; candidates include proteases, pectate lyases, lipases and various polysaccharide degrading enzymes. 相似文献
86.
Theendakara V Tromp G Kuivaniemi H White PS Panchal S Cox J Winters RS Riebeling P Tost F Hoeltzenbein M Tervo TM Henn W Denniger E Krause M Koksal M Kargi S Ugurbas SH Latvala T Shearman AM Weiss JS 《Human genetics》2004,114(6):594-600
Schnyders crystalline corneal dystrophy (SCCD) is a rare autosomal dominant eye disease with a spectrum of clinical manifestations that may include bilateral corneal clouding, arcus lipoides, and anterior corneal crystalline cholesterol deposition. We have previously performed a genome-wide linkage analysis on two large Swede-Finn families and mapped the SCCD locus to a 16-cM interval between markers D1S2633 and D1S228 on chromosome 1p36. We have collected 11 additional families from Finland, Germany, Turkey, and USA to narrow the critical region for SCCD. Here, we have used haplotype analysis with densely spaced microsatellite markers in a total of 13 families to refine the candidate interval. A common disease haplotype was observed among the four Swede-Finn families indicating the presence of a founder effect. Recombination results from all 13 families refined the SCCD locus to 2.32 Mbp between markers D1S1160 and D1S1635. Within this interval, identity-by-state was present in all 13 families for two markers D1S244 and D1S3153, further refining the candidate region to 1.58 Mbp. 相似文献
87.
88.
Joost den Haan Petra M. Visser Anjani E. Ganase Elfi E. Gooren Lucas J. Stal Fleur C. van Duyl Mark J. A. Vermeij Jef Huisman 《Coral reefs (Online)》2014,33(4):1003-1015
Algal turf communities are ubiquitous on coral reefs in the Caribbean and are often dominated by N2-fixing cyanobacteria. However, it is largely unknown (1) how much N2 is actually fixed by turf communities and (2) which factors affect their N2 fixation rates. Therefore, we compared N2 fixation activity by turf communities at different depths and during day and night-time on a degraded versus a less degraded coral reef site on the island of Curaçao. N2 fixation rates measured with the acetylene reduction assay were slightly higher in shallow (5–10-m depth) than in deep turf communities (30-m depth), and N2 fixation rates during the daytime significantly exceeded those during the night. N2 fixation rates by the turf communities did not differ between the degraded and less degraded reef. Both our study and a literature survey of earlier studies indicated that turf communities tend to have lower N2 fixation rates than cyanobacterial mats. However, at least in our study area, turf communities were more abundant than cyanobacterial mats. Our results therefore suggest that turf communities play an important role in the nitrogen cycle of coral reefs. N2 fixation by turfs may contribute to an undesirable positive feedback that promotes the proliferation of algal turf communities while accelerating coral reef degradation. 相似文献
89.
Christine Eulenburg Anna Suling Petra Neuser Alexander Reuss Ulrich Canzler Tanja Fehm Alexander Luyten Martin Hellriegel Linn Woelber Sven Mahner 《PloS one》2016,11(11)
Propensity scoring (PS) is an established tool to account for measured confounding in non-randomized studies. These methods are sensitive to missing values, which are a common problem in observational data. The combination of multiple imputation of missing values and different propensity scoring techniques is addressed in this work. For a sample of lymph node-positive vulvar cancer patients, we re-analyze associations between the application of radiotherapy and disease-related and non-related survival. Inverse-probability-of-treatment-weighting (IPTW) and PS stratification are applied after multiple imputation by chained equation (MICE). Methodological issues are described in detail. Interpretation of the results and methodological limitations are discussed. 相似文献
90.
Sumera Rizvi Daisaku Yamada Petra Hirsova Steven F. Bronk Nathan W. Werneburg Anuradha Krishnan Warda Salim Liang Zhang Eugenia Trushina Mark J. Truty Gregory J. Gores 《The Journal of biological chemistry》2016,291(15):8031-8047
Herein, we have identified cross-talk between the Hippo and fibroblast growth factor receptor (FGFR) oncogenic signaling pathways in cholangiocarcinoma (CCA). Yes-associated protein (YAP) nuclear localization and up-regulation of canonical target genes was observed in CCA cell lines and a patient-derived xenograft (PDX). Expression of FGFR1, -2, and -4 was identified in human CCA cell lines, driven, in part, by YAP coactivation of TBX5. In turn, FGFR signaling in a cell line with minimal basal YAP expression induced its cellular protein expression and nuclear localization. Treatment of YAP-positive CCA cell lines with BGJ398, a pan-FGFR inhibitor, resulted in a decrease in YAP activation. FGFR activation of YAP appears to be driven largely by FGF5 activation of FGFR2, as siRNA silencing of this ligand or receptor, respectively, inhibited YAP nuclear localization. BGJ398 treatment of YAP-expressing cells induced cell death due to Mcl-1 depletion. In a YAP-associated mouse model of CCA, expression of FGFR 1, 2, and 4 was also significantly increased. Accordingly, BGJ398 treatment was tumor-suppressive in this model and in a YAP-positive PDX model. These preclinical data suggest not only that the YAP and Hippo signaling pathways culminate in an Mcl-1-regulated tumor survival pathway but also that nuclear YAP expression may be a biomarker to employ in FGFR-directed therapy. 相似文献