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21.
CHRISTIAN LAFLAMME LOUIS GENDRON NATHALIE TURGEON GENEVIEVE FILION JIM HO CAROLINE DUCHAINE 《Journal of Rapid Methods and Automation in Microbiology》2009,17(1):80-102
Methods for the specific detection of Bacillus spores are needed in many situations such as the recognition of food poisoning. This study presents an experimental design in order to find the best combination of germination conditions leading to a rapid and detectable fluorescent in situ hybridization (FISH) signal from Bacillus cereus spores present in pure cultures and milk samples.
B. cereus ATCC 14579 and HER 1414 were incubated in 20 different growth media by using a combination of various germinants such as sugars, amino acids and dipicolinic acid. Also, three different germination factors were tested: incubation temperature, inoculum concentration and a heat shock treatment. Permeabilization procedure and hybridization time were optimized on the best germination condition found. B. cereus -specific FISH probes were validated under the optimized condition and in detection of spiked B. cereus spores in 1% ultra heat-treated milk samples. FISH-labeled cells were detected by using flow cytometry, and the results were confirmed by fluorescence microscopy. The optimal condition allows the detection of B. cereus spores in less than 2 h. Overall, a ninefold reduction in total time for detection was achieved when comparing with previous works. Therefore, the permeabilization and hybridization optimizations mentioned in this study are major improvements for the detection time of B. cereus spores.
By using the optimized conditions of germination/outgrowth, permeabilization and hybridization, the detection of 103 cfu/mL of Bacillus cereus spores using fluorescent in situ hybridization is possible within 2 h in milk sample. 相似文献
B. cereus ATCC 14579 and HER 1414 were incubated in 20 different growth media by using a combination of various germinants such as sugars, amino acids and dipicolinic acid. Also, three different germination factors were tested: incubation temperature, inoculum concentration and a heat shock treatment. Permeabilization procedure and hybridization time were optimized on the best germination condition found. B. cereus -specific FISH probes were validated under the optimized condition and in detection of spiked B. cereus spores in 1% ultra heat-treated milk samples. FISH-labeled cells were detected by using flow cytometry, and the results were confirmed by fluorescence microscopy. The optimal condition allows the detection of B. cereus spores in less than 2 h. Overall, a ninefold reduction in total time for detection was achieved when comparing with previous works. Therefore, the permeabilization and hybridization optimizations mentioned in this study are major improvements for the detection time of B. cereus spores.
PRACTICAL APPLICATIONS
By using the optimized conditions of germination/outgrowth, permeabilization and hybridization, the detection of 10
22.
GERALD MOSER CHRISTOPH LEUSCHNER DIETRICH HERTEL SOPHIE GRAEFE NATHALIE SOETHE SUSANNE IOST 《Global Change Biology》2011,17(6):2211-2226
Carbon storage and sequestration in tropical mountain forests and their dependence on elevation and temperature are not well understood. In an altitudinal transect study in the South Ecuadorian Andes, we tested the hypotheses that (i) aboveground net primary production (ANPP) decreases continuously with elevation due to decreasing temperatures, whereas (ii) belowground productivity (BNPP) remains constant or even increases with elevation due to a shift from light to nutrient limitation of tree growth. In five tropical mountain forests between 1050 and 3060 m a.s.l., we investigated all major above‐ and belowground biomass and productivity components, and the stocks of soil organic carbon (SOC). Leaf biomass, stemwood mass and total aboveground biomass (AGB) decreased by 50% to 70%, ANPP by about 70% between 1050 and 3060 m, while stem wood production decreased 20‐fold. Coarse and large root biomass increased slightly, fine root biomass fourfold, while fine root production (minirhizotron study) roughly doubled between 1050 and 3060 m. The total tree biomass (above‐ and belowground) decreased from about 320 to 175 Mg dry mass ha?1, total NPP from ca. 13.0 to 8.2 Mg ha?1 yr?1. The belowground/aboveground ratio of biomass and productivity increased with elevation indicating a shift from light to nutrient limitation of tree growth. We propose that, with increasing elevation, an increasing nitrogen limitation combined with decreasing temperatures causes a large reduction in stand leaf area resulting in a substantial reduction of canopy carbon gain toward the alpine tree line. We conclude that the marked decrease in tree height, AGB and ANPP with elevation in these mountain forests is caused by both a belowground shift of C allocation and a reduction in C source strength, while a temperature‐induced reduction in C sink strength (lowered meristematic activity) seems to be of secondary importance. 相似文献
23.
VIVIAN DE BUFFRÉNIL NATHALIE BARDET XABIER PEREDA‐SUBERBIOLA BAÂDI BOUYA 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2008,41(1):59-69
The histological organization of the vertebrae of the Maastrichtian squamate Pachyvaranus crassispondylus Arambourg, 1952 , was compared to that of various extant squamates, in order to further document the causes and functional consequences of the so-called 'pachyostosis', frequently observed in Late Cretaceous squamates. The vertebrae of Pachyvaranus are composed of the same basic bone tissue types as those of extant lizards and snakes. In particular, periosteal cortices are made of a pseudolamellar (or 'parallel-fibred') tissue, with radial vascular canals, Sharpey's fibres and conspicuous cyclic growth marks that are strictly identical to that found in extant varanids. Conversely, the vertebrae of Pachyvaranus are extremely compact, whereas those of extant squamates are very cancellous and lightly built. This difference is due to the absence in Pachyvaranus of a broad internal resorption field that, in extant lizards and snakes, transforms compact cortices into loose spongy formations. This absence of inner bone resorption typically corresponds to an osteosclerotic process. In Pachyvaranus , cortical hyperplasy, or pachyostosis stricto sensu , was restricted to the walls of the neural spine. Extreme vertebral porosity is likely to be a primitive condition in squamates, because all lizards and snakes examined in this study display this feature. Therefore, the high vertebral compactness observed in Pachyvaranus would be a derived condition arising from the loss (or de-differentiation) of a morphogenetic process: the broad internal resorption of the vertebrae. Possible palaeoecological bearings of these results are discussed. 相似文献
24.
CHRISTOPH SANDROCK NATHALIE FRAUENFELDER SIMONE VON BURG CHRISTOPH VORBURGER 《Molecular ecology resources》2007,7(6):1080-1083
The aphid parasitoid Lysiphlebus fabarum is suspected to form distinct, host‐associated lineages and exhibits poorly understood variation in reproductive mode including thelytokous and arrhenotokous populations. As a tool to study these issues, we developed 11 polymorphic microsatellite markers. The observed number of alleles ranged from two to 35, and the observed heterozygosity ranged from 0.01 to 0.64. Cross‐species amplification tests demonstrated their utility for several congeners, but revealed very limited applicability to more distantly related species. 相似文献
25.
CÉLINE CARRET FABIEN WALAS BERNARD CARCY NATHALIE GRANDE ÉRIC PRÉCIGOUT KARINA MOUBRI THEO P. SCHETTERS RÉ GORENFLOT 《The Journal of eukaryotic microbiology》1999,46(3):298-301
The parasites Babesia canis and Babesia gibsoni (phylum Apicomplexa) are responsible for canine babesiosis throughout the world. Babesia canis was previously described as a group of three biologically different subspecies, namely B. canis canis, B. canis vogeli, and B. canis rossi. We report partial sequences of small subunit ribosomal RNA gene (ssu-rDNA) of each subspecies amplified in vitro with primers derived from a semi-conserved region of the ssu-rDNA genes in other Babesia species. The polymerase chain reaction combined with a restriction fragment length polymorphism analysis, using HinfI and TaqI restriction enzymes, confirmed the separation of B. canis into three subspecies. These sequences were compared with previously published sequences of other Babesia species. A phylogenetic approach showed that the three subspecies of B. canis belong to the clade of Babesia species sensu stricto where B. canis canis clusters with B. canis rossi whereas B. canis vogeli might form a monophyletic group with the cluster B. divergens and B. odocoilei. Our results show that the three subspecies of B. canis can readily be differentiated at the molecular level and suggest that they might be considered as true species. 相似文献
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27.
JOSEPH A. TOBIAS NATHALIE SEDDON CLAIRE N. SPOTTISWOODE JOHN D. PILGRIM LINCOLN D. C. FISHPOOL NIGEL J. COLLAR 《Ibis》2010,152(4):724-746
Species are the fundamental units of biology, ecology and conservation, and progress in these fields is therefore hampered by widespread taxonomic bias and uncertainty. Numerous operational techniques based on molecular or phenotypic data have been designed to overcome this problem, yet existing procedures remain subjective or inconsistent, particularly when applying the biological species concept. We address this issue by developing quantitative methods for a classic technique in systematic zoology, namely the use of divergence between undisputed sympatric species as a yardstick for assessing the taxonomic status of allopatric forms. We calculated mean levels of differentiation in multiple phenotypic characters – including biometrics, plumage and voice – for 58 sympatric or parapatric species‐pairs from 29 avian families. We then used estimates of mean divergence to develop criteria for species delimitation based on data‐driven thresholds. Preliminary tests show that these criteria result in relatively few changes to avian taxonomy in Europe, yet are capable of extensive reassignment of species limits in poorly known tropical regions. While we recognize that species limits are in many cases inherently arbitrary, we argue that our system can be applied to the global avifauna to deliver taxonomic decisions with a high level of objectivity, consistency and transparency. 相似文献
28.
ANDREA SUNDERMANN CLAUDIA ANTONS NATHALIE CRON ARMIN W. LORENZ DANIEL HERING PETER HAASE 《Freshwater Biology》2011,56(8):1689-1702
1. River restoration has received considerable attention, with much recent focus on restoring river hydromorphology to improve impoverished aquatic communities. However, we still lack a clear understanding of the response of aquatic biota to river restoration. 2. We studied the effects of hydromorphological restoration on benthic invertebrate assemblages in 25 river sites in Germany using standardised methods. Restoration efforts were primarily aimed to restore habitat heterogeneity; correspondingly, habitat diversity increased at most sites. 3. Similarity of benthic invertebrate assemblages between restored and unrestored river sections was low (mean similarity was 0.32 for Jaccard and 0.46 for Sørensen). Community‐based metrics, such as the percentage of Ephemeroptera, Plecoptera and Trichoptera taxa, also differed between restored and unrestored sections. 4. Only three of the 25 restored sections were classified as having ‘good ecological quality’ class according to the European Water Framework Directive criteria; hence, poor water quality is probably one factor impeding recolonisation. 5. Our results show that isolated restoration measures do not necessarily result in positive effects on aquatic biota and that better understanding of the interconnectedness within a catchment is required before we can adequately predict biotic responses to structural river restoration. 相似文献
29.
A pooled DNA method was used to produce fully informative EST (expressed sequence tag)‐derived markers for the Picea genus. Nine markers were produced from 10 cDNA identified as candidates for cold tolerance or embryogenesis. Indels and SNPs (single nucleotide polymorphisms) were characterized from sequences obtained from pools of 10 individuals for each of the three species: Picea glauca (white spruce), Picea mariana (black spruce) and Picea abies (Norway spruce). Indels were present in 28% of the sequences and SNPs with a frequency greater than 10% were present on average in 1.2% of the positions. 相似文献
30.
NATHALIE NIQUIL GRETTA BARTOLI JOTARO URABE GEORGE A. JACKSON LOUIS LEGENDRE CHRISTINE DUPUY M. KUMAGAI 《Freshwater Biology》2006,51(8):1570-1585
1. A steady‐state model of carbon flows was developed to describe the summer planktonic food web in the surface mixed‐layer of the North Basin in Lake Biwa, Japan. This model synthesised results from numerous studies on the plankton of Lake Biwa. 2. An inverse analysis procedure was used to estimate missing flow values in a manner consistent with known information. Network analysis was applied to characterise emergent properties of the resulting food web. 3. The system strongly relied on flows related to detrital particles. Whereas primary production was mainly by phytoplankton >20 μm, microzooplankton were active and mainly ingested detritus and bacteria. 4. The main emergent property of the system was strong recycling, through either direct ingestion of non‐living material by zooplankton, or ingestion of bacteria after degradation of detritus to release dissolved organic carbon. 相似文献