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981.
Eduardo Costas Blanca Nieto Victoria Lopez-Rodas Conchita Salgado Miguel Toro 《Evolution; international journal of organic evolution》1998,52(2):610-613
We describe two competition experiments between clones of the dinoflagellate Alexandrium minutum. In the first experiment, two clones originating from a single haploid cell competed until one of the clones was almost driven to extinction. In the second experiment, these two clones were allowed to compete with the original populations, which were previously kept as cysts. The results indicate that an improvement of the competitive ability in both clones has occurred during the history of competition. This adaptation to competition must be attributed to selection acting on the new genetic variation that has arisen by mutation. 相似文献
982.
Alfredo Luis Borghi Laura Liliana Ramos Blanca J. Corallini de Bracalenti 《Mycopathologia》1981,74(3):187-190
With several fungi isolated from samples of soils obtained in the province of San Luis and in the province of Mendoza (Argentina), we employed a simple technique for the inoculation in the mice's foot in order to provoke the formation of endosporulated spherules.As a conclusion, it could be proved that all these strains classificated as Gimnoascaceae, genus Malbranchea sp. and Auxarthron zuffianum, produce what appear to be endosporulating spherules. The viability of the endospores was not demonstrated nor was disseminating infection produced. 相似文献
983.
Chemical and biological leaching of enargite 总被引:1,自引:0,他引:1
Enargite (Cu 3 AsS 4 ) was leached faster by bacteria in sulfuric acid medium (pH 1.6) with added ferric sulfate than by chemical leaching at the same or higher iron concentration. During chemical leaching with ferric iron, the copper dissolution rate decreased from an initial value of 0.03% per hour to a value of 0.002% per hour. Enargite is oxidized to elemental sulfur and dissolved arsenic (As 3+ and As 5+ ). Less than 10% of sulfur is oxidized to sulfate. The arsenic and copper dissolutions observed in bacterial leaching experiments suggest the existence of a specific bacterial action on the leaching of enargite, demonstrated by the ability of bacteria to oxidize enargite at very low concentration of dissolved iron and by the higher dissolution rate obtained in bacterial leaching compared to chemical ferric leaching. 相似文献
984.
985.
986.
N.m.r. spectroscopy (1H- and 13C-) of N-glycolylneuraminic acid, and of its interaction product with Ca2+ at pH 7, indicated that a 1:1 complex is formed, with a formation constant of 193 M?1 [compared to 121 M?1 for N-acetylneuraminic acid (1)]. From analysis of electric-field shifts, an approximate position of the Ca2+ ion in the complex is inferred, with the hydroxyl group of the N-glycolyl group providing the additional binding. Compound 1 was oxidized with sodium periodate, and 13C-n.m.r. spectroscopy was applied in an attempt to identify the aldehyde formed, and to demonstrate that the loss of the glycerol-1-yl side-chain (carbon atoms 8 and 9) decreases its Ca2+ ion-binding capacity. 相似文献
987.
Gómez-Alejandre S de la Blanca ES de Usera CA Rey-Stolle MF Hernández-Fuentes I 《International journal of biological macromolecules》2000,27(4):287-290
Density measurements of hyaluronic acid in different media and conditions have been made in order to determine the partial specific volumes, v0(2). We have studied the effects of temperature, type of cation, cation concentration, pH and solvent polarity on v0(2). 相似文献
988.
Guadalupe De la Rosa Alejandro Martínez-Martínez Helvia Pelayo José R Peralta-Videa Blanca Sanchez-Salcido Jorge L Gardea-Torresdey 《Plant Physiology and Biochemistry》2005,43(5):491-498
Tumbleweed (Salsola kali) is a desert plant species that has shown to be a potential Cd hyperaccumulator. In this study, the production of low-molecular weight thiols (LMWT) as a response to cadmium stress was determined in hydroponically grown seedlings exposed to 0, 45, 89, and 178 microM Cd(2+). The treatment of 89 microM Cd(2+) was tested alone and supplemented with an equimolar concentration of ethylenediaminetetraacetic acid (EDTA) to determine the effect of this chelating agent on Cd uptake and thiols production. After 6 days of growth, the Cd concentration in plant tissues was determined by using inductively coupled plasma/optical emission spectroscopy (ICP/OES). Results indicated that Cd uptake by plants was concentration-dependent. Plants treated with 178 microM Cd(2+), had 10+/-0.62, 9.7+/-1.4, and 4.3+/-0.83 mmol Cd kg(-1) dry tissue in roots, stems, and leaves, respectively. The production of thiols was dependent on Cd concentration in tissues. According to the stoichiometry performed, plants treated with Cd concentrations up to 178 muM produced 0.131+/-0.02, and 0.087+/-0.012 mmol SH per mmol Cd present in roots and stems. In leaves, the production of thiols decreased at the highest Cd concentration tested. Thus, up to 89 microM Cd in the media, 0.528+/-0.004 mmol SH per mmol Cd in leaf tissues were produced. EDTA equimolar to Cd reduced both Cd uptake and thiols production. Catalase activity (CAT) (EC 1.11.1.6) was significantly depressed at the lowest Cd concentration. None of the conditions tested affected biomass or plant elongation. 相似文献
989.
Serafin Valverde Javier Escudero J. Cristóbal López Rosa Ma Rabanal 《Phytochemistry》1985,24(1):111-113
Two new terpenoids, 20(S),24(R)-epoxy-dammar-12,25-diol-3-one and 12-methoxy-11,7-dihydroxydehydroabietane, were isolated from the roots of Salvia bicolor. 相似文献
990.
Ruiz de Escudero I Estela A Escriche B Caballero P 《Applied and environmental microbiology》2007,73(1):337-340
The potential of Bacillus thuringiensis Cry proteins to control the grape pest Lobesia botrana was explored by testing first-instar larvae with Cry proteins belonging to the Cry1, Cry2, and Cry9 groups selected for their documented activities against Lepidoptera. Cry9Ca, a toxin from B. thuringiensis, was the protein most toxic to L. botrana larvae, followed in decreasing order by Cry2Ab, Cry1Ab, Cry2Aa, and Cry1Ia7, with 50% lethal concentration values of 0.09, 0.1, 1.4, 3.2, and 8.5 microg/ml of diet, respectively. In contrast, Cry1Fa and Cry1JA were not active at the assayed concentration (100 microg/ml). In vitro binding and competition experiments showed that none of the toxins tested (Cry1Ia, Cry2Aa, Cry2Ab, and Cry9C) shared binding sites with Cry1Ab. We conclude that either Cry1Ia or Cry9C could be used in combination with Cry1Ab to control this pest, either as the active components of B. thuringiensis sprays or expressed together in transgenic plants. 相似文献