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11.
Ingrid Ahrenholtz Michael G. Lorenz Wilfried Wackernagel 《Archives of microbiology》1994,161(2):176-183
A quantitative endonuclease assay, which relies on the introduction of single and double strand breaks into supercoiled plasmid DNA, was used to study the activity of the extracellular nuclease of Serratia marcescens SM6 in buffer and in groundwater. The parallel enzyme concentration-dependent production of relaxed and linear plasmid molecules suggests that the nuclease produces single and double strand breaks in duplex DNA. Bovine serum albumin stimulated the nuclease activity towards DNA and RNA and increased the stability of the enzyme against thermal inactivation. The DNase activity at 4 °C and 50 °C was almost half of that at the optimum temperature (37 °C). The nuclease was active in groundwater, although the specific activity was lower than in buffer. In a groundwater aquifer microcosm, mineral-adsorbed transforming DNA was substantially less accessible to the nuclease than was dissolved DNA. The data suggest that the extracellular nuclease of Serratia marcescens may contribute to DNA turnover in the environment and that adsorption of DNA to minerals provides protection against the nuclease.Abbreviations GW groundwater
GWA groundwater aquifer 相似文献
12.
Wilfried Bautsch 《Molecular biotechnology》1994,2(1):29-44
Macrorestriction mapping is often the first step toward a thorough physical and genetic characterization of a bacterial genome.
The problem of deducing the order of partially or completely digested macrorestriction fragments to yield a physical genome
map may readily be solved by applying twodimensional pulsed-field gel electrophoresis (2D-PFGE) techniques. These powerful
methods are quick and technically easy to perform; specifically, they are independent of DNA probes and should therefore be
applicable to any bacterial species irrespective of its prior genetic characterization. In this article, detailed step-by-step
protocols are given to set up, run, and evaluate 2D pulsed-field gels. Two basic methods are described: partial/complete 2D
gels of one restriction enzyme and complete/complete 2D gels of two different restriction enzymes. Other topics include preparation
of bacterial genomic DNA, screening for suitable rare-cutting restriction enzymes and determination of optimal running conditions.
Accompanied by many notes, these protocols are meant to offer the novice a sound and rapid access to these important methods. 相似文献
13.
Thomas Bartels und Wilfried Meyer 《Journal of Ornithology》1993,134(3):301-307
Zusammenfassung Unter Einsatz einer neuartigen, direkt vergrößernden Röntgentechnologie wurde die Konstruktion des Schnabelskeletts von schlupfreifen Jungvögeln untersucht. Wie die bei Verwendung sog. Mikrofokus-Röntgengeräte erzielten Röntgenaufnahmen erkennen lassen, weist das Schnabelskelett der Schlüpflinge — unabhängig vom Entwicklungsmodus — bei allen untersuchten Formen einen recht einheitlichen Bau auf. Sowohl der Ossifikationsgrad der Kiefer als auch die spezifische Osteoarchitektur der Knochenelemente des Schnabelapparates, insbesondere im Bereich der Substantia spongiosa des Os praemaxillare können als anatomische Anpassungen an die beim Sprengen der Eischale auftretenden mechanischen Belastungen des Kieferskeletts gewertet werden.
Construction principles of the beak skeleton in the hatchling
Summary The structure of the beak skeleton of hatchlings was analysed using a new direct magnifying X-ray technique. The application of these microfocus X-ray systems reveals a quite uniform construction of the beak skeleton in the hatchlings, independent from the mode of development of the bird species groups studied (precocial, altricial etc.). The amount of ossification as well as the specific osteoarchitecture of the jaw bones of the beak apparatus — especially in the region of Substantia spongiosa of the Os praemaxillare — may be considered as an anatomical adaptation to mechanical stress of the jaw bones during picking of the eggshell.相似文献
14.
Van Lint Johan Van Damme Jo Billiau Alfons Merlevede Wilfried Vandenheede Jackie R. 《Molecular and cellular biochemistry》1993,127(1):171-177
The signal transduction initiated by the human cytokine interleukin-8 (IL-8), the main chemotactic cytokine for neutrophils, was investigated and found to encompass the stimulation of protein kinases. More specifically, IL-8 caused a transient, dose and time dependent activation of a Ser/Thr kinase activity towards myelin basic protein (MBP) and the MBP-derived peptide APRTPGGRR patterned after the specific concensus sequence in MBP for ERK enzymes. The activated MBP kinase was furthermore identified as an extracellular signal regulated kinase (ERK1) based on several criteria such as substrate specificity, molecular weight, activation-dependent mobility shift, and recognition by anti-ERK antibodies. For comparison, the chemotactic response of neutrophils to a stimulus of bacterial origin (fMet-Leu-Phe or fMLP) was also examined and found to involve the activation of a similar ERK enzyme. The present data clearly indicate that in terminally differentiated, non-proliferating human cells, the MBP kinase/ERK activity can serve other purposes than mitogenic signaling, and that processes such as chemotaxis, induced by bacterial peptides as well as by human cytokines like IL-8, involve the regulation of ERK enzyme.Abbreviations IL-8
interleukin-8
- fMLP
fMet-Leu-Phe
- MBP
myelin basic protein
- ERK
extracellular signal regulated kinase
- MAP2
microtubule-associated protein 2
- PK-A
cAMP dependent protein kinase
- PKI
protein kinase inhibitor
- PMSF
phenyl-methanesulfonyl fluoride
- PVDF
poly-vinylidene difluoride
- HBSF
Hank's buffered salt solution
- DAB
3,3-diaminobenzidine tetrahydrochloride
- PNPP
p-nitrophenyl-phosphate
- HSA
human serum albumin
- EGTA
[ethylenebis (oxyethylenenitrilo)]tetraacetic acid
- SDS-PAGE
sodium dodecyl sulfate polyacrylamide gel electrophoresis 相似文献
15.
Lucie Mahaut Philippe Choler Pierre Denelle Eric Garnier Wilfried Thuiller Jens Kattge Servane Lemauviel-Lavenant Sandra Lavorel François Munoz Delphine Renard Josep M. Serra-Diaz Nicolas Viovy Cyrille Violle 《Global Ecology and Biogeography》2023,32(4):561-572
Aim
It is crucial to monitor how the productivity of grasslands varies with its temporal stability for management of these ecosystems. However, identifying the direction of the productivity–stability relationship remains challenging because ecological stability has multiple components that can display neutral, positive or negative covariations. Furthermore, evidence suggests that the direction of the productivity–stability relationship depends on the biotic interactions and abiotic conditions that underlie ecosystem productivity and stability. We decipher the relationships between grassland productivity and two components of its stability in four habitat types with contrasting environments and flora.Location
France.Time period
2000–2020.Major taxa
Grassland plant species.Methods
We used c. 20,000 vegetation plots spread across French permanent grasslands and remotely sensed vegetation indices to quantify grassland productivity and temporal stability. We decomposed stability into constancy (i.e., temporal invariability) and resistance (i.e., maximum deviation from average) and deciphered the direct and indirect effects of abiotic (namely growing season length and nitrogen input) and biotic (namely plant taxonomic diversity, trait diversity and community-weighted mean traits) factors on productivity–stability relationships using structural equation models.Results
We found a positive relationship between productivity and constancy and a negative relationship between productivity and resistance in all habitats. Abiotic factors had stronger effects on productivity and stability compared with biotic factors. A longer growing season enhanced grassland productivity and constancy. Nitrogen input had positive and negative effects on grassland productivity and resistance, respectively. Trait values affected the constancy and resistance of grassland more than taxonomic and trait diversity, with effects varying from one habitat to another. Productivity was not related to any biotic factor.Main conclusions
Our findings reveal how vital it is to consider both the multiple components of stability and the interaction between environment and biodiversity to gain an understanding of the relationships between productivity and stability in real-world ecosystems, which is a crucial step for sustainable grassland management. 相似文献16.
17.
A physical and genetic map of Neisseria meningitidis B1940 总被引:2,自引:0,他引:2
Martin Gäher Kerstin Einsiedler Torsten Crass & Wilfried Bautsch 《Molecular microbiology》1996,19(2):249-259
A physical map of the chromosome of Neisseria meningitidis B1940 has been constructed by one- and two-dimensional pulsed-field gel electrophoresis techniques. Complete macrorestriction maps for the enzymes Nhe I (16 sites), Sgf I (13 sites), Sfi I (11 sites) and I-Ceu I (4 sites), as well as a partial restriction map for the restriction enzyme Spe I (15 of c. 28 sites) could be established. Altogether, 59 restriction sites were mapped on a single circular chromosome of 2.3 Mbp. By restriction endonuclease digestion and Southern hybridization of cloned genetic markers, 39 genetic loci were assigned to this map. Comparison with the metabolic maps of Neisseria gonorrhoeae MS11-N198 and FA1090 revealed a high degree of conservation in the arrangement of gene loci among these two species, although four out of 24 genetic loci are located at different chromosomal positions, indicating several genomic rearrangements. 相似文献
18.
Cyanopeptolin S, a sulfate-containing depsipeptide from a water bloom of Microcystis sp. 总被引:1,自引:0,他引:1
Clemens Jakobi Lukas Oberer Charles Quiquerez Wilfried A. König Jürgen Weckesser 《FEMS microbiology letters》1995,129(2-3):129-133
Abstract A new sulfated, cyclic depsipeptide, called cyanopeptolin S, from Microcystis sp. was isolated from a water bloom in the Auensee/Leipzig (Germany). The depsipeptide had a relative molecular mass of 925 and contained l-arginine, l-threonine, l-isoleucine, N-methyl-l-phenylalanine, a l-glutamic acid-δ-aldehyde ring system and a sulfated d-configurated glyceric acid as a side chain. The structure was elucidated by means of two-dimensional 1 H and 13 C nuclear magnetic resonance spectroscopy, fast atom bombardment mass spectroscopy, Fourier transformed infrared spectroscopy and combined gas-liquid chromatography/mass spectrometry. Cyanopeptolin S inhibited trypsin with an IC50 ≤ 0.2 μg ml−1 . 相似文献
19.
The enantiomers of rac-2,2′-diiodobiphenyl were separated by liquid chromatography on microcrystalline triacetylcellulose. The conformational lability, a large separation factor α, and a suitable capacity factor k′(+) of this biphenyl allowed us to convert the racemate into 90% of enantiomerically pure (-)-2,2′-diiodobiphenyl and 10% of pure (+)-2,2′-diiodobiphenyl, respectively, by a series of in situ racemization-elution cycles. The much better retained (+)-enantiomer was racemized on the chromatographic column at 50°C after the less retained (-)-enantiomer has already been eluted at 8°C. © 1995 Wiley-Liss, Inc. 相似文献
20.
Werner Lösecke Wilfried Naumann Prof. Dr. sc. Günther Sterba Dr. h. c. 《Cell and tissue research》1984,235(1):201-206
Summary The secretion of the subcommissural organ (SCO) of the rat was studied by means of immunocytochemistry at the electron-microscopic level with the use of (1) the polar embedding medium Lowicryl K4M at -30° C, (2) the protein A-gold technique, and (3) a rabbit antiserum against bovine Reissner's fiber (see Sterba et al. 1981).Two different substructures of the ependymal and the hypendymal SCO-cells display a positive immunocytochemical reaction: (1) sacs containing flocculent secretion, which originate from the granular endoplasmic reticulum, and (2) vacuoles filled with fine granular secretion, which are pinched off from the Golgi apparatus. The secretory material of the sacs and the vacuoles is discharged both (i) apically into the cerebrospinal fluid and (ii) basally into intercellular spaces of the SCO-hypendyma. The apically released secretion is condensed to a lamina-like formation, which more caudally assumes the form of Reissner's fiber. The route of the basally released secretion remains, however, vague. The periodically striated bodies, which were thought to be morphological mediators of the discharge of the secretion into the capillaries, are never labeled by gold particles.Supported by grants from the Ministry for Science and Technology of the German Democratic RepublicThe expert technical assistance of Mrs. B. Wolff, Mrs. S. Mehnert, Mrs. E. Siebert, Mrs. Ch. Schneider, and Mrs. I. Seifert is gratefully acknowledged 相似文献