排序方式: 共有114条查询结果,搜索用时 15 毫秒
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Flockhart AF Tree JJ Xu X Karpiyevich M McAteer SP Rosenblum R Shaw DJ Low CJ Best A Gannon V Laing C Murphy KC Leong JM Schneiders T La Ragione R Gally DL 《Molecular microbiology》2012,83(1):208-223
This study has identified horizontally acquired genomic regions of enterohaemorrhagic Escherichia coli O157:H7 that regulate expression of the type III secretion (T3S) system encoded by the locus of enterocyte effacement (LEE). Deletion of O-island 51, a 14.93 kb cryptic prophage (CP-933C), resulted in a reduction in LEE expression and T3S. The deletion also had a reduced capacity to attach to epithelial cells and significantly reduced E. coli O157 excretion levels from sheep. Further characterization of O-island 51 identified a novel positive regulator of the LEE, encoded by ecs1581 in the E. coli O157:H7 strain Sakai genome and present but not annotated in the E. coli strain EDL933 sequence. Functionally important residues of ECs1581 were identified based on phenotypic variants present in sequenced E. coli strains and the regulator was termed RgdR based on a motif demonstrated to be important for stimulation of gene expression. While RgdR activated expression from the LEE1 promoter in the presence or absence of the LEE-encoded regulator (Ler), RgdR stimulation of T3S required ler and Ler autoregulation. RgdR also controlled the expression of other phenotypes, including motility, indicating that this new family of regulators may have a more global role in E. coli gene expression. 相似文献
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Gijsen HJ Berthelot D De Cleyn MA Geuens I Brône B Mercken M 《Bioorganic & medicinal chemistry letters》2012,22(2):797-800
The transient receptor potential A1 (TRPA1) channel has been implicated in a number of inflammatory and nociceptive processes, and antagonists of the TRPA1 receptor could offer a potential treatment for conditions such as inflammatory or neuropathic pain, airway disorders, and itch. In a high throughput screen aimed at the identification of TRPA1 antagonists, 4-phenyl-2-thioxo-1,2,3,4-tetrahydro-indeno[1,2-d]pyrimidin-5-one (1) was identified as a potent TRPA1 receptor antagonist. A series of analogous tricyclic 3,4-dihydropyrimidine-2-thiones has been prepared via the multi-component Biginelli reaction and subsequent derivatization. This has led to TRPA1 antagonists with potencies around 10nM for both rat and human derived TRPA1 receptors. The activity was shown to reside exclusively in the 4R-enantiomers. 相似文献
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J. L. L. Rakels A. G. M. Schneiders A. J. J. Straatho J. J. Heijnen 《Biocatalysis and Biotransformation》1996,13(3):179-188
Competitive parallel reactions with opposite enantioselectivity are presented as a strategy to enhance the enantiomeric product purity in enzymatic kinetic resolution. Lipase-catalyzed simultaneous hydrolysis and amidation of racemic methy 12-chloropropionate led to significantly improved amide yield and enantiomeric excess. Process results can be controlled by changing the hydrolysis/amidation reaction rates through variation of the solvent and the initial amine concentration. This is described by a kinetic model. 相似文献
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Felix Normann Patrick Weigelt Christine Gehrig-Downie S. Robbert Gradstein Harrie J.M. Sipman André Obregon Jörg Bendix 《Ecological Indicators》2010,10(6):1111-1118
Recent work on bryophyte diversity in lowland forests of northern South America has suggested the existence of a new type of cloud forest, the “tropical lowland cloud forest” (LCF). LCF occurs in river valleys with high air humidity and radiation fog, and is rich in epiphytes. We explored the lichenological characteristics of putative LCF in a lowland area (200–400 m a.s.l.) near Saül, central French Guiana, using macrolichens (including large crustose species) as indicator taxa. We analyzed macrolichen diversity on 16 trees in two 1 ha plots, in LCF and in lowland rain forest without fog (LRF). Sampling efficiency was ca. 80% in both forest types. Canopies of both LRF and LCF were richer in lichen species than understory trunks. Species richness of macrolichens was rather similar in the two forest types but species composition was significantly different. Cyanolichen richness in LCF was ca. 2.5 times higher than in LRF; in contrast, LRF had 4 times more species of green-algal Parmeliaceae. Our study suggests that cyanolichens except for Coccocarpiaceae serve as indicators of LCF. We explain the detected diversity patterns by differences in water availability due to fog precipitation and higher humidity. This is indicated by the higher relative air humidity in the lowland cloud forest, which was >6% higher than in the rain forest. 相似文献
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Castor phospholipid:diacylglycerol acyltransferase facilitates efficient metabolism of hydroxy fatty acids in transgenic Arabidopsis 总被引:3,自引:0,他引:3
Producing unusual fatty acids (FAs) in crop plants has been a long-standing goal of green chemistry. However, expression of the enzymes that catalyze the primary synthesis of these unusual FAs in transgenic plants typically results in low levels of the desired FA. For example, seed-specific expression of castor (Ricinus communis) fatty acid hydroxylase (RcFAH) in Arabidopsis (Arabidopsis thaliana) resulted in only 17% hydroxy fatty acids (HFAs) in the seed oil. In order to increase HFA levels, we investigated castor phospholipid:diacylglycerol acyltransferase (PDAT). We cloned cDNAs encoding three putative PDAT enzymes from a castor seed cDNA library and coexpressed them with RcFAH12. One isoform, RcPDAT1A, increased HFA levels to 27%. Analysis of HFA-triacylglycerol molecular species and regiochemistry, along with analysis of the HFA content of phosphatidylcholine, indicates that RcPDAT1A functions as a PDAT in vivo. Expression of RcFAH12 alone leads to a significant decrease in FA content of seeds. Coexpression of RcPDAT1A and RcDGAT2 (for diacylglycerol acyltransferase 2) with RcFAH12 restored FA levels to nearly wild-type levels, and this was accompanied by a major increase in the mass of HFAs accumulating in the seeds. We show the usefulness of RcPDAT1A for engineering plants with high levels of HFAs and alleviating bottlenecks due to the production of unusual FAs in transgenic oilseeds. 相似文献
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Protective antiviral immune responses to pseudorabies virus induced by DNA vaccination using dimethyldioctadecylammonium bromide as an adjuvant 总被引:3,自引:0,他引:3
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van Rooij EM Glansbeek HL Hilgers LA te Lintelo EG de Visser YE Boersma WJ Haagmans BL Bianchi AT 《Journal of virology》2002,76(20):10540-10545
To enhance the efficacy of a DNA vaccine against pseudorabies virus (PRV), we evaluated the adjuvant properties of plasmids coding for gamma interferon or interleukin-12, of CpG immunostimulatory motifs, and of the conventional adjuvants dimethyldioctadecylammonium bromide in water (DDA) and sulfolipo-cyclodextrin in squalene in water. We demonstrate that a DNA vaccine combined with DDA, but not with the other adjuvants, induced significantly stronger immune responses than plasmid vaccination alone. Moreover, pigs vaccinated in the presence of DDA were protected against clinical disease and shed significantly less PRV after challenge infection. This is the first study to demonstrate that DDA, a conventional adjuvant, enhances DNA vaccine-induced antiviral immunity. 相似文献
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Summary A new technique for transfer of organelles to plant cells is presented. The organelles are removed from the donor protoplast by micromanipulation and microinjected directly into the acceptor cells. First results obtained by this technique for transfer of chloroplasts and fluorescently labelled mitochondria are presented. 相似文献
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Magnus N Osnes Lucy van Dorp Ola B Brynildsrud Kristian Alfsnes Thamarai Schneiders Kate E Templeton Koji Yahara Francois Balloux Dominique A Caugant Vegard Eldholm 《Molecular biology and evolution》2021,38(4):1249
The Neisseria gonorrhoeae multilocus sequence type (ST) 1901 is among the lineages most commonly associated with treatment failure. Here, we analyze a global collection of ST-1901 genomes to shed light on the emergence and spread of alleles associated with reduced susceptibility to extended-spectrum cephalosporins (ESCs).The genetic diversity of ST-1901 falls into a minor and a major clade, both of which were inferred to have originated in East Asia. The dispersal of the major clade from Asia happened in two separate waves expanding from ∼1987 and 1996, respectively. Both waves first reached North America, and from there spread to Europe and Oceania, with multiple secondary reintroductions to Asia.The ancestor of the second wave acquired the penA 34.001 allele, which significantly reduces susceptibility to ESCs. Our results suggest that the acquisition of this allele granted the second wave a fitness advantage at a time when ESCs became the key drug class used to treat gonorrhea. Following its establishment globally, the lineage has served as a reservoir for the repeated emergence of clones fully resistant to the ESC ceftriaxone, an essential drug for effective treatment of gonorrhea.We infer that the effective population sizes of both clades went into decline as treatment schemes shifted from fluoroquinolones via ESC monotherapy to dual therapy with ceftriaxone and azithromycin in Europe and the United States. Despite the inferred recent population size decline, the short evolutionary path from the penA 34.001 allele to alleles providing full ceftriaxone resistance is a cause of concern. 相似文献