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1.
Divergence time analyses in the coffee family (Rubiaceae) have all relied on the same Gentianales crown group age estimate, reported by an earlier analysis of the asterids, for defining the upper age bound of the root node in their analyses. However, not only did the asterid analysis suffer from several analytical shortcomings, but the estimate itself has been used in highly inconsistent ways in these Rubiaceae analyses. Based on the original data, we here reanalyze the divergence times of the asterids using relaxed-clock models and 14 fossil-based minimum age constraints. We also expand the data set to include an additional 67 taxa from Rubiaceae sampled across all three subfamilies recognized in the family. Three analyses are conducted: a separate analysis of the asterids, which completely mirrors the original asterid analysis in terms of taxon sample and data; a separate analysis of the Gentianales, where the result from the first analysis is used for defining a secondary root calibration point; and a combined analysis where all taxa are analyzed simultaneously. Results are presented in the form of a time-calibrated phylogeny, and age estimates for asterid groups, Gentianales, and major groups of Rubiaceae are compared and discussed in relation to previously published estimates. Our updated age estimates for major groups of Rubiaceae provide a significant step forward towards the long term goal of establishing a robust temporal framework for the divergence of this biologically diverse and fascinating group of plants.  相似文献   
2.
Escherichia coli ppGpp synthetase II activity requires spoT   总被引:21,自引:0,他引:21  
Escherichia coli has two enzymes catalyzing the synthesis of guanosine tetraphosphate (ppGpp), designated ppGpp synthetase I (PSI = RelA) and II (PSII), whose activities are regulated differently. Until now, the gene for PSII had not been identified. Here, an E. coli relA1 strain that expresses lacZ from an rrnB P1 promoter was used to screen mutants with increased beta-galactosidase activity on 5-bromo-4-chloro-3-indoyl beta-D-galactoside indicator plates at 30 degrees C. About 15% of the mutants obtained in this manner had reduced levels of ppGpp at 30 degrees C and no detectable ppGpp at 43 degrees C. These mutants did not form colonies at 42 degrees C on minimal medium plates and had elevated ribosome concentrations and higher growth rates at 30 degrees C. Genetic mapping by phage P1 transduction and complementation analyses showed that the mutations were located in spoT and that they were recessive. Specific inhibition of SpoT-dependent ppGpp degradation activity with picolinic acid showed that two of the mutants tested were deficient in ppGpp synthesis activity. These results indicate that spoT is required for PSII activity, suggesting that spoT encodes both ppGpp degradation and synthesis activities and that these two functions can be affected independently by mutation.  相似文献   
3.
(1) The relation between the effects of the sulfur-substituted fatty acid analogue, tetradecylthioacetic acid (TTA), dexamethasone and insulin on enzyme induction and growth rate was studied in Morris hepatoma 7800 C1 cells in culture. (2) The activities of the cynanide-insensitive palmitoyl-CoA oxidase and palmitoyl-CoA hydrolase were induced about 2-fold by 50 microM TTA after 72 h of treatment. Catalase was less induced and NADPH-cytochrome-c2 reductase, glucose-6-phosphate dehydrogenase and lactate dehydrogenase were unaffected by the fatty acid analogue. (3) Dexamethasone (250 nM) induced the same enzymes as did TTA, but was a less efficient than 50 microM TTA. However, in combination their effects were more than additive, resulting in 4-7-fold increases. (4) Insulin (400 nM) counteracted the inductive effects of both TTA and dexamethasone on all enzymes except for lactate dehydrogenase, which was induced by the combination of all three compounds. (5) TTA inhibited the growth rate of the cells, and this effect was potentiated by dexamethasone and counteracted by insulin. (6) The enzyme inductions were similar in exponential and plateau phases of growth, indicating that these processes were independently affected by the three compounds.  相似文献   
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An lagerndem Winterknoblauch ist unter außenluft‐(x + 6, 5 bzw. 8, 3 °C) und maschinengekühlten Bedingungen (x‐1 . . .‐2 °C) in zwei Lagerperioden die Entwicklung der einzelnen Fäuleerreger verfolgt und in Abhängigkeit von der Lagerdauer statistisch quantifiziert worden. An Hand des Masseanteiles befallener Zwiebeln und der Befallsintensität wird eine zunehmende Ausbreitung von Penicillium spp. und einer Gruppe mit Befall durch mehrere Fäuleerreger unter beiden Lagerbedingungen und von einer Botrytis‐Species (vermutlich B. porri Buchw.) im maschinengekühlten Lager belegt. Fäuleverluste durch Helminthosporium allii Campanile und Bakterien zeigen dagegen mit fortschreitender Lagerdauer einen abnehmenden Verlauf. Mit Eintreten von lagerungsbedingter Seneszenz steigen die Verluste progressiv an. Kaltlagerbedingungen verzögern dagegen ihre Ausbreitung. Die Verluste durch alle Fäulerreger (Fäule gesamt) zeigen eine gleichmäßige Zunahme während der Lagerdauer.  相似文献   
6.
A simple method for preparation of methyl-labelled (-) carnitine   总被引:2,自引:0,他引:2  
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8.
Formation of branched chain acylcarnitines in mitochondria   总被引:5,自引:0,他引:5  
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10.
The quality of milk products is threatened by the formation of biofilms of thermophilicstreptococci on the internal surfaces of plate heat exchangers used in milk processing. Althoughattachment to stainless steel surfaces is one of the first stages in the development of a biofilm, themechanisms involved in attachment have not been reported. The cell surface properties of 12strains of thermophilic streptococci were examined to determine their importance in attachment tostainless steel surfaces. Hydrophobicity, extracellular polysaccharide production and cell surfacecharge varied between the different strains but could not be related to numbers attaching. Treatingthe cells with sodium metaperiodate, lysozyme or trichloroacetic acid to disrupt cell surfacepolysaccharide had no effect on attachment. Treatment with trypsin or sodium dodecyl sulphate toremove cell surface proteins resulted in a 100-fold reduction in the number of bacteria attaching.This result suggests that the surface proteins of the thermophilic streptococci are important intheir attachment to stainless steel.  相似文献   
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