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71.
Molecular epidemiology of avian pathogenic Escherichia coli (APEC) isolated from colisepticemia in poultry 总被引:6,自引:0,他引:6
The molecular biology and epidemiology of 150 avian pathogenic Escherichia coli strains (APEC) isolated from septicemic poultry in Germany was investigated by serotyping, pulsed field gel electrophoresis (PFGE), and polymerase chain reaction (PCR). Only 49.6% of the isolates could be grouped to serogroups O1, O2, and O78. Macrorestriction analyses data revealed two large clonal groups (clusters I and II) among the APEC strains with a similarity of 60.9% to each other. An association between restriction pattern and serogroup or origin of the strains was only present in a few subgroups of each clusters I and II, but was not evident. In contrast, our data revealed distinct combinations of virulence-associated genes in that 51.2% of the O2-strains harboured a combination of the genes fyuA, irp2, iucD, tsh, vat, fimC, and colV and 36.4% of the O78-strains possessed the same gene combination with exception of vat. With 34 different gene combinations the non-O1, -O2, -O78 isolates revealed a higher variability in their virulence gene pattern than O1-, O2-, and O78-strains with 6, 13, and 9 patterns, respectively. Our data indicate only a limited association between the virulence gene pattern and the serogroup of APEC strains and question the sensitivity of O-typing for APEC identification without the application of further diagnostic tools. Although a limited number of APEC clones exist, horizontal gene transfer seems to be common in these pathogens. These findings strengthen further research on the population structure of APEC and may be the reason for the lack of clear definition of this common E. coli pathotype. 相似文献
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Goehring NW Trong PK Bois JS Chowdhury D Nicola EM Hyman AA Grill SW 《Science (New York, N.Y.)》2011,334(6059):1137-1141
In the Caenorhabditis elegans zygote, a conserved network of partitioning-defective (PAR) polarity proteins segregates into an anterior and a posterior domain, facilitated by flows of the cortical actomyosin meshwork. The physical mechanisms by which stable asymmetric PAR distributions arise from transient cortical flows remain unclear. We present evidence that PAR polarity arises from coupling of advective transport by the flowing cell cortex to a multistable PAR reaction-diffusion system. By inducing transient PAR segregation, advection serves as a mechanical trigger for the formation of a PAR pattern within an otherwise stably unpolarized system. We suggest that passive advective transport in an active and flowing material may be a general mechanism for mechanochemical pattern formation in developmental systems. 相似文献
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Jennifer Eiermann BVSc Kristin Kirkby-Shaw DVM MS PhD DACVS-SA DACVSMR CCRT Richard B. Evans PhD Sebastian C. Knell Dr med vet DECVS Michael P. Kowaleski DVM DACVS DECVS Philipp A. Schmierer Dr med vet DECVS Mary S. Bergh DVM DACVS DACVSMR Jason Bleedorn DVM MS DACVS Laura C. Cuddy MVB MS DACVS-SA DECVS DACVSMR DECVSMR MRCVS Nina R. Kieves DVM DACVS-SA DACVSMR CCRT Peter Lotsikas DVM DACVS DACVSMR Antonio Pozzi DVM MS DACVS DECVS DACVSMR 《Veterinary surgery : VS》2020,49(1):80-87
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Soil nitrogen dynamics after slurry injection in field trials: Evaluation of a soil sampling strategy 下载免费PDF全文
Matthias Westerschulte Carl‐Philipp Federolf Herbert Pralle Dieter Trautz Gabriele Broll Hans‐Werner Olfs 《植物养料与土壤学杂志》2015,178(6):923-934
Slurry injection below maize seeds is a rather new application technique developed to improve the nitrogen use efficiency of liquid organic manure. To enable the characterization of the spatial and temporal soil mineral nitrogen (SMN) dynamics after slurry injection, the present study aims to develop an appropriate soil sampling strategy. Three consecutive experiments were conducted. The first testing of the soil sampling approach was conducted in an existing field trial where the slurry was injected down to a depth of 12 cm (upper rim) below the soil surface. The soil profile (75 cm wide) centered below the maize row was sampled grid‐like to a depth of 90 cm. Around the injection zone, soil monoliths (SM) were sampled using a purpose‐built soil shovel. Below the SMs and in the interrow space (15 and 30 cm distance to the row) a standardized auger procedure was performed. The second experiment aimed at improving the sampling strategy with a focus on sample homogenization quality and necessary sample sizes per pooled sample. Furthermore, the risk of a carryover of slurry components along the soil core due to drilling an auger through a slurry band was analyzed. In the third experiment this improved sampling strategy was validated. Results from the first testing of the sampling procedure showed that the strategy is suitable, although some problems occurred (especially the high spread in values among the replications causing high coefficients of variation (CV) of mostly 40–60%). The improvement trial revealed that due to the high gradient of SMN concentration in the direct range of the injection zone an intensive homogenization of these samples is required. Suitable sample sizes (twelve auger samples and six soil monolith samples per pooled sample) have to be collected to obtain reliable SMN values. Drilling an auger through a slurry band to sample subjacent soil layers has to be avoided. Following this enhanced sampling strategy, in the final validation trial the spread in values were considerably reduced and resulted in CV values of mostly < 20%. The developed sampling strategy enables the characterization of the spatial and temporal SMN dynamics when slurry has been band‐injected below a maize row. The method can be transferred to other row crops and different slurry injection spacing. 相似文献
79.
Ahmad Fakhro Susanne von Bargen Martina Bandte Carmen Büttner Philipp Franken Dietmar Schwarz 《European journal of plant pathology / European Foundation for Plant Pathology》2011,129(4):579-590
As Pepino mosaic virus has become a pathogen of major importance in worldwide tomato production, information is needed on possible differences between
the sensitivity of cultivars towards infection. Furthermore, it is important what hosts other than Solanaceae may be virus reservoirs and are, therefore, threats for tomato cultivation. Two PepMV isolates (PepMV-Sav, E397, a European
tomato isolate and PV-0554, a Peruvian pepino isolate) differing in their origin and virulence were used for several experiments
to investigate these issues. The response to mechanical inoculation with PepMV was studied using 25 tomato cultivars, seven
indicator plant species, and nine other possible horticultural host plants. Symptom development after infection with PepMV
was monitored and the virus was detected by DAS-ELISA and IC-RT-PCR. Garlic and broad bean were shown to be additional hosts
of PepMV depending on the virus isolate. Nicotiana benthamiana seems to be the most sensitive indicator among all tested indicator plants developing symptoms. Both PepMV isolates infected
all tested tomato cultivars. Development of disease symptoms depended on the cultivar and the virus isolate but symptoms were
not visible in all cases. None of the cultivars showed tolerance against the two isolates but two responded with a lower susceptibility
at an absorbance level of 0.2 (healthy control 0.09). It was observed that some cultivars grown hydroponically showed also
lower losses in biomass and yield. Data indicated a correlation between absorbance level in DAS-ELISA and reduction in total
tomato growth. 相似文献
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