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981.
Biarrotte-Sorin S Maillard AP Delettré J Sougakoff W Arthur M Mayer C 《Structure (London, England : 1993)》2004,12(2):257-267
Members of the FemABX protein family are novel therapeutic targets, as they are involved in the synthesis of the bacterial cell wall. They catalyze the addition of amino acid(s) on the peptidoglycan precursor using aminoacylated tRNA as a substrate. We report here the high-resolution structure of Weissella viridescens L-alanine transferase FemX and its complex with the UDP-MurNAc-pentapeptide. This is the first structure example of a FemABX family member that does not possess a coiled-coil domain. FemX consists of two structurally equivalent domains, separated by a cleft containing the binding site of the UDP-MurNAc-pentapeptide and a long channel that traverses one of the two domains. Our structural studies bring new insights into the evolution of the FemABX and the related GNAT superfamilies, shed light on the recognition site of the aminoacylated tRNA in Fem proteins, and allowed manual docking of the acceptor end of the alanyl-tRNAAla. 相似文献
982.
Maximiliano Wilda María Ángeles Lavoria Adrián Giráldez Olga Lucía Franco-Mahecha Florencia Mansilla Matías Érguiz Marcela Elvira Iglesias Alejandra Victoria Capozzo 《Biologicals》2012,40(6):415-420
Challenge with live pathogens could be substituted by serology for many veterinary diseases, however little progress has been made in the development of alternative batch vaccine potency tests for fish. This study reports the development and preliminary validation of a single-dilution filtration-assisted chemiluminometric immunoassay (SD FAL-ELISA) applied to measure anti Piscirickettsia salmonis IgM in individual or pooled serum and mucus samples. The assay was set up to test a single-dilution of the sample. Serum SD FAL-ELISA yielded a sensitivity of 90% and a specificity of 96%. SD FAL-ELISA was applied to evaluate pooled and individual samples from P. salmonis challenge assessments. Relative-light units values (RLU) obtained by SD FAL-ELISA were proportional to antibody levels in serum. RLU values obtained from pooled and individual serum samples increased with the observed relative percent survival (RPS) values, indicating a correlation between protection and specific IgM levels. Results obtained for specific IgM in mucus samples was not related to the RPS, but discriminated the vaccine that yielded high RPS (86.4%) from the others (40.9 and 54.5%). This is the first report on the development of an indirect high-throughput serological assessment for P. salmonis vaccine potency testing using both pooled or individual serum and cutaneous mucus samples. 相似文献
983.
Protein-bound dinitrosyl-iron complexes (DNIC) in rat whole blood and organs were studied after intravenous injection of this substance with glutathione ligand (DNIC-GH). The effect of DNIC-GH injection on NO level (including NO physiological forms) in hydrophobic areas of rat tissues was also studied in normal physiological blood circulation condition. It has been shown, that after DNIC-GH injection the concentration of protein-bound DNICs in rat whole blood and organs rapidly reached maximum values, and then gradually decreased, that pointed to decomposition of DNIC molecules, coupled with NO release. At the beginning of the experiment the rates of DNIC decay in rat heart and lung were substantially higher, as compared with those in liver and kidney. By spin trappping it has been demonstrated that DNIC-GH, as a source of NO physiological forms (including S-nitrosothiols), in normal physiological blood circulation influence heart more selectively, as compared with the other organs. 相似文献
984.
Csepregi K Valasek A Pénzes Á Tóth Z Kiss ÉÍ Kerepesi I Horváth B Nagy I Fekete C 《Journal of bacteriology》2012,194(5):1263
Although certain rare actinomycetes have been recognized as prolific sources of bioactive natural products, their potential for producing biologically active metabolites still remains unexplored. With the aim of gaining global insights into the genetic background and the metabolic capability of Saccharomonospora azurea SZMC 14600, whole-genome sequencing was performed. 相似文献
985.
986.
C. BÉRÉNOS P. SCHMID‐HEMPEL K. MATHIAS WEGNER 《Journal of evolutionary biology》2009,22(10):2049-2056
Standard epidemiological theory predicts that parasites, which continuously release propagules during infection, face a trade‐off between virulence and transmission. However, little is known how host resistance and parasite virulence change during coevolution with obligate killers. To address this question we have set up a coevolution experiment evolving Nosema whitei on eight distinct lines of Tribolium castaneum. After 11 generations we conducted a time‐shift experiment infecting both the coevolved and the replicate control host lines with the original parasite source, and coevolved parasites from generation 8 and 11. We found higher survival in the coevolved host lines than in the matching control lines. In the parasite populations, virulence measured as host mortality decreased during coevolution, while sporeload stayed constant. Both patterns are compatible with adaptive evolution by selection for resistance in the host and by trade‐offs between virulence and transmission potential in the parasite. 相似文献
987.
LAURIE A. HALL PER J. PALSBØLL STEVEN R. BEISSINGER JAMES T. HARVEY MARTINE BÉRUBÉ MARTIN G. RAPHAEL S. KIM NELSON RICHARD T. GOLIGHTLY LAURA MCFARLANE‐TRANQUILLA SCOTT H. NEWMAN M. ZACHARIAH PEERY 《Molecular ecology》2009,18(24):5074-5085
Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (FST~ 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post‐breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent‐offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants. 相似文献
988.
Does the disturbance hypothesis explain the biomass increase in basin‐wide Amazon forest plot data? 总被引:1,自引:0,他引:1
M. GLOOR O. L. PHILLIPS J. J. LLOYD S. L. LEWIS Y. MALHI T. R. BAKER G. LÓPEZ‐GONZALEZ J. PEACOCK S. ALMEIDA A. C. ALVES
De OLIVEIRA E. ALVAREZ I. AMARAL L. ARROYO G. AYMARD O. BANKI L. BLANC D. BONAL P. BRANDO K.‐J. CHAO J. CHAVE N. DÁVILA T. ERWIN J. SILVA A. Di FIORE T. R. FELDPAUSCH A. FREITAS R. HERRERA N. HIGUCHI E. HONORIO E. JIMÉNEZ T. KILLEEN W. LAURANCE C. MENDOZA A. MONTEAGUDO A. ANDRADE D. NEILL D. NEPSTAD P. NÚÑEZ VARGAS M. C. PEÑUELA A. PEÑA CRUZ A. PRIETO N. PITMAN C. QUESADA R. SALOMÃO MARCOS SILVEIRA M. SCHWARZ J. STROPP F. RAMÍREZ H. RAMÍREZ A. RUDAS H.
Ter STEEGE N. SILVA A. TORRES J. TERBORGH R. VÁSQUEZ G.
Van Der HEIJDEN 《Global Change Biology》2009,15(10):2418-2430
Positive aboveground biomass trends have been reported from old-growth forests across the Amazon basin and hypothesized to reflect a large-scale response to exterior forcing. The result could, however, be an artefact due to a sampling bias induced by the nature of forest growth dynamics. Here, we characterize statistically the disturbance process in Amazon old-growth forests as recorded in 135 forest plots of the RAINFOR network up to 2006, and other independent research programmes, and explore the consequences of sampling artefacts using a data-based stochastic simulator. Over the observed range of annual aboveground biomass losses, standard statistical tests show that the distribution of biomass losses through mortality follow an exponential or near-identical Weibull probability distribution and not a power law as assumed by others. The simulator was parameterized using both an exponential disturbance probability distribution as well as a mixed exponential–power law distribution to account for potential large-scale blowdown events. In both cases, sampling biases turn out to be too small to explain the gains detected by the extended RAINFOR plot network. This result lends further support to the notion that currently observed biomass gains for intact forests across the Amazon are actually occurring over large scales at the current time, presumably as a response to climate change. 相似文献
989.
Walsh SE Maillard JY Russell AD Catrenich CE Charbonneau DL Bartolo RG 《Journal of applied microbiology》2003,94(2):240-247
AIMS: This study investigates the antimicrobial activity and mode of action of two natural products, eugenol and thymol, a commonly utilized biostatic agent, triclocarban (TCC), and two surfactants, didecyldimethylammonium chloride (DDDMAC) and C10-C16 alkyldimethyl amine N-oxides (ADMAO). METHODS AND RESULTS: Methods used included: determination of minimum inhibitory concentrations (MICs), lethal effect studies with suspension tests and the investigation of sub-MIC concentrations on growth of E. coli, Staph. aureus and Ps. aeruginosa using a Bioscreen microbiological analyser. Leakage of intracellular constituents and the effects of potentiating agents were also investigated. Only DDDMAC was bactericidal against all of the organisms tested. Eugenol, thymol and ADMAO showed bacteriostatic and bactericidal activity, but not against Ps. aeruginosa. TCC was only bacteristatic against Staph. aureus, but like the other agents, it did affect the growth of the other organisms in the Bioscreen experiments. All of the antimicrobial agents tested were potentiated by the permeabilizers to some extent and leakage of potassium was seen with all of the agents except TCC. CONCLUSIONS: DDDMAC was bactericidal against all organisms tested and all compounds had some bacteriostatic action. Low level static effects on bacterial growth were seen with sub-MIC concentrations. Membrane damage may account for at least part of the mode of action of thymol, eugenol, DDDMAC and ADMAO. SIGNIFICANCE AND IMPACT OF THE STUDY: The ingredients evaluated demonstrated a range of bactericidal and bacteriostatic properties against the Gram-negative and -positive organisms evaluated and the membrane (leakage of intracellular components) was implicated in the mode of action for most (except TCC). Sub-MIC levels of all ingredients did induce subtle effects on the organisms which impacted bacterial growth, even for those which had no true inhibitory effects. 相似文献
990.