排序方式: 共有47条查询结果,搜索用时 15 毫秒
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Chapman MR Robinson LS Pinkner JS Roth R Heuser J Hammar M Normark S Hultgren SJ 《Science (New York, N.Y.)》2002,295(5556):851-855
Amyloid is associated with debilitating human ailments including Alzheimer's and prion diseases. Biochemical, biophysical, and imaging analyses revealed that fibers produced by Escherichia coli called curli were amyloid. The CsgA curlin subunit, purified in the absence of the CsgB nucleator, adopted a soluble, unstructured form that upon prolonged incubation assembled into fibers that were indistinguishable from curli. In vivo, curli biogenesis was dependent on the nucleation-precipitation machinery requiring the CsgE and CsgF chaperone-like and nucleator proteins, respectively. Unlike eukaryotic amyloid formation, curli biogenesis is a productive pathway requiring a specific assembly machinery. 相似文献
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Aspholm-Hurtig M Dailide G Lahmann M Kalia A Ilver D Roche N Vikström S Sjöström R Lindén S Bäckström A Lundberg C Arnqvist A Mahdavi J Nilsson UJ Velapatiño B Gilman RH Gerhard M Alarcon T López-Brea M Nakazawa T Fox JG Correa P Dominguez-Bello MG Perez-Perez GI Blaser MJ Normark S Carlstedt I Oscarson S Teneberg S Berg DE Borén T 《Science (New York, N.Y.)》2004,305(5683):519-522
Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations. 相似文献
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Ring species, which consist of two reproductively isolated forms connected by a chain of intergrading populations, have often been described as examples of speciation despite gene flow between populations, but this has never been demonstrated. We used amplified fragment length polymorphism (AFLP) markers to study gene flow in greenish warblers (Phylloscopus trochiloides). These genetic markers show distinct differences between two reproductively isolated forms but gradual change through the ring connecting these forms. These findings provide the strongest evidence yet for "speciation by force of distance" in the face of ongoing gene flow. 相似文献
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Jean-Baptiste Chesneau Elisabeth Le Net Staffan Berg 《European Journal of Forest Research》2012,131(1):73-80
The development of ToSIA (tool for sustainability impact assessment of the Forest Wood Chain) involved to measure economic,
social and environmental indicators of all transformation processes belonging to the Forest Wood Chain (FWC). In this context,
a specific tool has been developed to measure indicators related to almost all transport processes of each European FWC. The
aim of this article is to describe the approach and the method used to set up this tool and also to illustrate some of its
applications through an example. The example shows how the tool can deal with major transport issues by determining, in a
German case, the distances (respectively, 330 and 280 km) setting the economic advantage to use rail and inland waterways
instead of road. Moreover, it evaluates the implications of such changes in term of Green House Gas reduction (respectively,
50 and 56%). 相似文献
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Silvestre García de Jalón Paul J. Burgess Anil Graves Gerardo Moreno Jim McAdam Eric Pottier Sandra Novak Valerio Bondesan Rosa Mosquera-Losada Josep Crous-Durán Joao H. N. Palma Joana A. Paulo Tania S. Oliveira Eric Cirou Yousri Hannachi Anastasia Pantera Régis Wartelle Sonja Kay Nina Malignier Philippe Van Lerberghe Penka Tsonkova Jaconette Mirck Mercedes Rois Anne Grete Kongsted Claudine Thenail Boki Luske Staffan Berg Marie Gosme Andrea Vityi 《Agroforestry Systems》2018,92(4):829-848
Whilst the benefits of agroforestry are widely recognised in tropical latitudes few studies have assessed how agroforestry is perceived in temperate latitudes. This study evaluates how stakeholders and key actors including farmers, landowners, agricultural advisors, researchers and environmentalists perceive the implementation and expansion of agroforestry in Europe. Meetings were held with 30 stakeholder groups covering different agroforestry systems in 2014 in eleven EU countries (Denmark, France, Germany, Greece, Hungary, Italy, Netherlands, Portugal, Spain, Sweden and the United Kingdom). In total 344 valid responses were received to a questionnaire where stakeholders were asked to rank the positive and negative aspects of implementing agroforestry in their region. Improved biodiversity and wildlife habitats, animal health and welfare, and landscape aesthetics were seen as the main positive aspects of agroforestry. By contrast, increased labour, complexity of work, management costs and administrative burden were seen as the most important negative aspects. Overall, improving the environmental value of agriculture was seen as the main benefit of agroforestry, whilst management and socio-economic issues were seen as the greatest barriers. The great variability in the opportunities and barriers of the systems suggests enhanced adoption of agroforestry across Europe will be most likely to occur with specific initiatives for each type of system. 相似文献
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Anahit Penesyan Francesco Ballestriero Malak Daim Staffan Kjelleberg Torsten Thomas Suhelen Egan 《Marine drugs》2013,11(1):40-49
A common limitation for the identification of novel activities from functional (meta) genomic screens is the low number of active clones detected relative to the number of clones screened. Here we demonstrate that constructing libraries with strains known to produce bioactives can greatly enhance the screening efficiency, by increasing the “hit-rate” and unmasking multiple activities from the same bacterial source. 相似文献
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Toward a systems approach to understanding plant cell walls 总被引:2,自引:0,他引:2
Somerville C Bauer S Brininstool G Facette M Hamann T Milne J Osborne E Paredez A Persson S Raab T Vorwerk S Youngs H 《Science (New York, N.Y.)》2004,306(5705):2206-2211
One of the defining features of plants is a body plan based on the physical properties of cell walls. Structural analyses of the polysaccharide components, combined with high-resolution imaging, have provided the basis for much of the current understanding of cell walls. The application of genetic methods has begun to provide new insights into how walls are made, how they are controlled, and how they function. However, progress in integrating biophysical, developmental, and genetic information into a useful model will require a system-based approach. 相似文献
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Honey-Marie C. de la Giroday Allan L. Carroll B. Staffan Lindgren Brian H. Aukema 《Landscape Ecology》2011,26(8):1097-1110
Mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae), is a forest insect that undergoes intermittent population eruptions, causing
landscape-level mortality to mature pines. Currently, an outbreak covers over 16.3 million ha of British Columbia and Alberta
in western Canada. Recent incursion into the jack pine (Pinus banksiana Lamb.) of northwestern Alberta threatens further range expansion through the boreal forest to central and eastern Canada.
The spread from British Columbia into northwestern Alberta has been facilitated by above-canopy dispersal of the insect by
meso-scale atmospheric currents. At these scales, dispersing D. ponderosae may behave like inert particles, causing terrain-induced tropospheric convective and advective currents to influence population
dispersal and establishment. We use spatial point process regression models to examine the association of meso-scale variables,
including landscape features and their orientations, habitat suitability, elevation and treatment efforts, with occurrence
of D. ponderosae infestations in 2004, 2005, and 2006. Infestations of D. ponderosae primarily established in canyons and valleys, before moving into more open-sloped areas. Southwestern slopes of midslope
ridges and small hills, southwest facing open slopes, and valleys that run in a northeast–southwest cardinal direction were
positively associated with higher intensities of infestation. This study provides insight into the influences of complex terrain
on landscape disturbance by a forest insect, and can be used to prioritize areas for potential management. 相似文献