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The adsorption and binding of plasmid p34S DNA on four different colloidal fractions from a Brown soil and clay minerals in the presence of various Ca2+ concentrations, the ability of bound DNA to transform competent cells of CaCl2-treated Escherichia coli, and the resistance of bound DNA to degradation by DNase I were studied. DNA adsorption on soil colloids and clay minerals was promoted in the presence of Ca2+. Kaolinite exhibited the highest adsorption affinity for DNA among the examined soil colloids and clay minerals. In comparison with organo-mineral complexes (organic clays) and fine clays (<0.2 μm), DNA was tightly adsorbed by H2O2-treated clays (inorganic clays) and coarse clays (0.2-2 μm). The transformation efficiency of bound DNA increased with increasing concentrations of Ca2+ at which soil colloid or clay mineral-DNA complexes were formed. DNA bound by kaolinite showed the lowest transformation efficiency, and especially no transformants were observed with kaolinite-DNA complex prepared at 5-100 mM Ca2+. Compared to organic clays and fine clays, DNA bound on inorganic clays and coarse clays showed a lower capacity to transform E. coli at different Ca2+ concentrations. The presence of soil colloids and minerals provided protection to DNA against degradation by DNase I. Montmorillonite, organic clays and fine clays showed stronger protective effects for DNA than inorganic clays and coarse clays. The protection mechanisms as well as the differences in transforming efficiency of plasmid DNA molecules bound on various soil colloidal particles are discussed. The information obtained in this study is of fundamental significance for the understanding of the horizontal dissemination of recombinant DNA and the fate of extracellular DNA in soil environments. 相似文献
3.
Surface chemical properties of soil colloids are the important factor affecting soil fertility and genesis.To provide scientific basis for soil genetic classification,promotion of soil fertility and reasonable fertilizqation,the specific surface area and electric charge of soil colloids in relation to clay minerals and organic matter are further discussed on the basis of the results obtained from the studies on surface chemical properties of soil colloids in five main soils of China.Results from the studies show that the effect of clay minerals and organic matter on the surface chemical properties of soil colloids is very complicated because the siloxane surface,hydrated oxide surface and organic matter surface do not exist separately,but they are always mixed together and influenced each other.The understanding of the relationship among clay minerals,organic matter and surface chemical properties of soil colloids depends upon further study of the relevant disciplines of soil science,especially the study on the mechanisms of organo-mineral complexes. 相似文献
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F. De Coninck 《Geoderma》1980,24(2):101-128
Current explanations of the formation of spodic horizons do not accomodate all features of the horizons in their natural state. In this paper, a more complete explanation of major mechanisms is proposed, using two principles of colloid chemistry: (1) organic substances may form hydrophylic colloids with surface charges, and (2) the hydrophylic character and negative surface charges determine the dispersibility of the colloids. The hydrophylic character is due to the presence of hydrophylic radicals as parts of the organic compounds in soils. The surface charges are the result of dissociation of -COOH and possibly phenol-OH radicals.The neutralization of the surface charge can in principle occur: (1) through electrostatic or physical adsorption and (2) through chemisorption. The first case is typical for monovalent alkali cations. The adsorbed cations are distributed in a double layer, which favours dispersion. Chemisorption occurs mostly with polyvalent cations. This process corresponds in reality to the formation of organo-metallic compounds. It results in a relatively complete disappearance of the double layer and in the formation of large immobile “polymerized” organo-metallic compounds. Because these compounds contain much hydrophylic water, they form a gel. Transition into the solid state is accompanied by the loss of most of the hydration water. The dehydration may be induced by a decrease in thickness of the double layer. At a certain stage of the dehydration process, Van der Waals bonds and protonic bridges can form and bring about a certain degree of hydrophoby.In soils, mobile organic substances are formed during breakdown of plant remains. If at the top of the mineral soil enough polyvalent cations, especially Al and Fe, are available, the mobile organic substances formed are immobilized immediately and no migration occurs. In case insufficient amounts of Al and/or Fe are available to completely immobilize the mobile compounds, these cations are complexed by the mobile compounds and transported downward. Immobilization may occur at some depth through supplementary fixation of cations, through dessication or on arrival at a level with different ionic concentration.In nature, spodic horizons range from loose, with many roots, to very cemented with few roots. These differences can be related to changes in microstructure. Loose spodic horizons have a predominance of polymorphic pellets and aggregates, whereas organans or monomorphic coatings prevail in cemented horizons. The former horizons have many features suggesting major biological influences during their formation, viz., high numbers of roots, thorough mixing of the organic units with clay and silt, the presence of pedotubules and relatively young mean residence times. The latter horizons have features consistent with organo-metallic compounds immobilized in a gel-state, viz., the coatings are strongly cracked, indicating the transition of a gel into a solid; they contain much Al or Al plus Fe but very little or no Si, and the mean residence time is considerably higher than in loose horizons.The two processes seem to operate simultaneously during the formation of spodic horizons and their relative intensities determine the composition of each spodic horizon at any moment in its evolution. As long as the biological activity predominates, the horizon remains loose; if the accumulation of mobile organo-metallic compounds starts to prevail, the horizon is gradually cemented and fossilized. 相似文献
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Adsorption and desorption of salmon sperm DNA on four different colloidal fractions from Brown Soil and clay minerals were studied. The adsorption isotherms of DNA on the examined soil colloids and minerals conformed to the Langmuir equation. The amount of DNA adsorbed followed the order: montmorillonite?fine inorganic clay>fine organic clay>kaolinite>coarse inorganic clay>coarse organic clay. A marked decrease in the adsorption of DNA on organic clays and montmorillonite was observed with the increase of pH from 2.0 to 5.0. Negligible DNA was adsorbed by organic clays above pH 5.0. As for inorganic clays and kaolinite, a slow decrease in DNA adsorption was found with increasing pH from 2.0 to 9.0. The results implied that electrostatic interactions played a more important role in DNA adsorption on organic clays and montmorillonite. Magnesium ion was more efficient than sodium ion in promoting DNA adsorption on soil colloids and minerals. DNA molecules on soil colloids and minerals were desorbed by sequential washing with 10 mM Tris, 100 mM NaCl and 100 mM phosphate at pH 7.0. A percentage of 53.7-64.4% of adsorbed DNA on organic clays and montmorillonite was released, while only 10.7-15.2% of DNA on inorganic clays and kaolinite was desorbed by Tris and NaCl. The percent desorption of DNA from inorganic clays, organic clays, montmorillonite and kaolinite by phosphate was 39.7-42.2, 23.6-28.8, 29.7 and 11.4%, respectively. Data from this work indicated that fine clays dominate the amount of DNA adsorption and coarse clays play a more important role in the binding affinity of DNA in soil. Organic matter may not favor DNA adsorption in permanent-charge soil. The information obtained is of fundamental significance for the understanding of the ultimate fate of extracellular DNA in soil. 相似文献
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土壤矿物对有机质的吸附与固定机制研究进展 总被引：6，自引：1，他引：6
鉴于土壤有机质在生态系统及碳储存方面的重要性,关于土壤矿物对土壤有机质的吸附与固定机理方面的研究越来越受到了学术界的广泛关注。本文综述了近年来报道较多的土壤矿物对土壤有机质的吸附机制,以及主要影响因素。在众多矿物类型中,水合铁、铝氧化物及黏土矿物对有机质的吸附性较强,配体交换、络合、氢键、阳离子桥接、缩合及范德华力作用是土壤矿物与有机质之间的主要作用机制。土壤pH是影响矿物表面电荷及吸附位点的关键因素,进而影响矿物对有机质的吸附。土壤矿物表面的有机质含量对其继续吸附有机质具有一定的影响。吸附态有机质大多呈层状结构,越接近矿物表面的有机质与土壤矿物的结合越紧密。土壤有机质的稳定性受有机质与矿物间的作用力影响,一般而言,以化学键合吸附在矿物表面的有机质最稳定,其次为直接与矿物表面作用的电子"供体-受体"机制,范德华力和静电作用稳定性较差。近年来,随着分析设备和技术的进步,一些新的表征与探测方法(如热重分析、差示扫描量热法、傅里叶转换红外光谱、扫描电子显微镜、原子力显微镜、扫描透射X射线显微镜、中子散射技术等)被用于"矿物-有机质"结合机制的研究中,这些新手段毫无疑问会帮助更好地认识矿物与有机质间的作用机理。关于微生物在矿物吸附有机质、"矿物-有机质"复合体形成和演化过程中所起的作用,研究相对较少,但很明显这是至关重要的。 相似文献
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土壤有机-无机复合体是土壤肥力的物质基础之一,不仅依随成土过程而发生变化,人类耕作利用也可产生影响。 相似文献
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本文讨论我国几种主要土壤胶体的NH4+吸附特征。土壤胶体对NH4+的吸附符合两种表面Langmuir方程。土壤胶体对NH4+的结合能力强弱顺序是:黄棕壤>黑土、(土娄)土>红壤>砖红壤,而NH4+的解吸率大小顺序与此相反。Langmuir吸附方程参数K1与土壤胶体的粘粒矿物组成有关,并与土壤胶体对NH4+的相对偏好性(A值)呈正相关。Langmuir参数(M1+M2)与土壤胶体的CEC呈正相关,去有机质(OM.)前后△K1与△OM.呈反相关。去有机质可增加土壤胶体对NH4+的偏好性。土壤胶体的NH4+吸附和解吸特征决定于其组成和表面性质,并受有机无机复合作用的影响。永久电荷吸附位对NH4+的偏好性较强,而可变电荷吸附位则较弱。 相似文献
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G. Pietramellara J. Ascher F. Borgogni M. T. Ceccherini G. Guerri P. Nannipieri 《Biology and Fertility of Soils》2009,45(3):219-235
The review discusses origin, state and function of extracellular DNA in soils and sediments. Extracellular DNA can be released
from prokaryotic and eukaryotic cells and can be protected against nuclease degradation by its adsorption on soil colloids
and sand particles. Laboratory experiments have shown that DNA adsorbed by colloids and sand particles can be taken up by
prokaryotic competent cells and be involved in natural transformation. Most of these experiments have been carried out under
artificial conditions with pure DNA molecules and pure adsorbing matrices, but in soils and sediments, pure surface-reactive
colloids are not present and DNA is present with other cellular components (wall debris, proteins, lipids, RNA, etc.) especially
if released after cell lysis. The presence of inorganic compounds and organic molecules on both soil particles and DNA molecules
can influence the DNA adsorption, degradation and transformation of competent cells. Extracellular DNA can be used as C, N
and P sources by heterotrophic microorganisms and plays a significant role in bacterial biofilm formation. The nucleotides
and nucleosides originated from the degradation of extracellular DNA can be re-assimilated by soil microorganisms. Extracellular
DNA in soil can be leached and moved by water through the soil profile by capillarity. In this way, the extracellular DNA
secreted by a cell can reach a competent bacterial cell far from the donor cell. Finally, the characterisation of extracellular
DNA can integrate information on the composition of the microbial community of soil and sediments obtained by analysing intracellular
DNA. 相似文献
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The adsorption of the herbicide thiazafluron, 1,3-dimethyl-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)urea, by three smectites, illite, kaolinite, ferrihydrite and the clay fraction of an illitic soil (54.9% illite, 17.0% montmorillonite and 24.9% kaolinite) and a montmorillonitic soil (33.9% illite, 55.0% montmorillonite and 11.1% kaolinite) has been determined. Thiazafluron adsorbed on neither kaolinite nor iron oxide. The adsorption isotherms on smectites and illite conformed to the Freundlich equation. Values of Kf-obtained for smectites were larger than for the illite and increased as the layer charge of the smectite decreased. Desorption of thiazafluron on smectites was shown to be highly irreversible. Adsorption isotherms of thiazafluron on different homoionic montmorillonite samples suggest an important role of the exchangeable cations in the adsorption. Infrared spectra and X-ray diffraction analysis of the complexes of thiazafluron with homoionic montmorillonites indicated that thiazafluron adsorbs in the interlamellar space of the smectites, mainly by substitution of water molecules associated with the exchangeable cations through the carbonyl-amide group and formation of H-bonds or waterbridge between the NH group of the amide and the basal oxygens of the montmorillonite. The illitic soil clay adsorbed more of the herbicide than the montmorillonitic one did, suggesting that illite and montmorillonite may be present in soils in altered forms giving rise to different adsorption capacities from those of the pure minerals. 相似文献
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R.G. Burns 《Soil biology & biochemistry》1982,14(5):423-427
The activity of any particular enzyme in soil is a composite of activities associated with various biotic and abiotic components, e.g. proliferating cells, latent cells, cell debris, clay minerals, humic colloids and the soil aqueous phase. The location of the enzyme is at least partially determined by such factors as the size and solubility of its substrate, the species of microorganism, and the physical and chemical nature of the soil colloids. However, enzymes may change location with time, for example, many hydrolases are intracellular sensu stricto but are also found associated with cell debris and clay and organic colloids. There are difficulties in quantifying the various activities, but this may be possible by employing different types of assays, the prudent use of controls and the study of crude enzyme extracts from soil.Enzymes bound to clay and humic colloids (the immobilized or accumulated enzyme fraction) have a residual activity not found in enzymes free in the soil aqueous phase. However, the mere adsorption of enzymes to soil surfaces does not guarantee subsequent activity, and it appears that some mechanism of association with the humic polymer offers the best form of protection, yet permits the retention of enzyme activity.The catalytic activity of extracellular enzymes is discussed and a possible relationship between soil microorganisms, exogenous substrates and immobilized enzymes is suggested. 相似文献
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I. I. Sudnitsyn 《Eurasian Soil Science》2006,39(5):492-497
Close correlation between different soil properties (the total and capillary pressure of soil water, the content of bound water, the cation exchange capacity, the hydration heat of the exchangeable cations, the wetting heat of the soil, and the energy of the ion detachment from the substances composing the soil solid phase) derived from the mathematical analysis of experimental data confirm the hypothesis about the prevailing effect of exchangeable cations on water binding in soils enriched with clay minerals (of the montmorillonite and hydromica groups) in which the cation exchange capacity of the colloidal fraction is higher than 0.5 meq/g of colloids. 相似文献
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This study represents an assessment of some of the key factors influencing the mobility of Al(III) and its displacement in acid soils. This assessment is based on the effect of pH and other solution variables on the solubility of Al(III) and its complex formation with OH?, F? and organic ligands (fulvates and humates). Above all, the adsorption behavior of Al(III) on iron(III) (hydr)oxides and on SiO2 on one hand, and the adsorption of organic acids and of humic substances on mineral surfaces on the other hand was investigated. Adsorption is interpreted in terms of surface complex formation equilibria; the mass law constants derived permit the modeling of adsorption as a function of solution variables. It is illustrated that the distribution of oxides and hydroxides in the soil profile affects the pH buffering, determines the mobility of the organic acids while the mobility of Al(III) is primarily governed by the formation and dissolution of Al(III) (hydr)oxides. 相似文献
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M. Novoszad M. H. Gerzabek H. Lischka G. Haberhauer & M. Jakusch 《European Journal of Soil Science》2007,58(1):26-33
The present work investigates the impact of site management on the retention of organic compounds in soil in a long‐term field experiment and focuses on the role of particle size fractions. Specifically, we studied the influence of long‐term farming practices on the soil’s ability to adsorb five hydrophobic organic compounds (HOCs), specifically naphthalene derivatives (naphthalene, 1‐naphthol, 1‐naphthylamine, 1‐hydroxy‐2‐naphthoic acid, 1,4‐naphthoquinone). We examined the sorption on soil and its particle‐size fractions with varying amounts and origins of organic matter in soil amended with farmyard manure and mineral fertilizers over more than 40 years. The soil organic matter had no significant impact on the sorption behaviour of the HOCs. Adsorption on the clay and silt fraction provided a deeper insight into the mechanisms and indicates a strong affinity with adsorption sites of the mineral phase. Naphthalene derivatives with hydrogen atoms in their functional groups adsorbed more strongly than other compounds on to soils containing smaller amounts of organic carbon. Desorption experiments with five organic extractants showed partitioning models for HOCs between extractant and soil surface. Only in experiments with the most polar extractant, formamide, did we observe an influence of the compound’s functional groups on the desorption mechanisms. Column experiments with a HPLC‐system and on‐line UV‐detection proved to be a satisfactory alternative to batch experiments. This approach should enable investigations of adsorption with larger numbers of compounds and soils at the same time. 相似文献
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The adsorption at pH's 4, 6 and 8 of adenine, guanine, cytosine, thymine and uracil on clays (montmorillonite, illite and kaolinite), Fe- and Al-oxides (goethite, hematite and gibbsite), a soil, and on a laboratory-prepared fulvic acid-montmorillonite complex was investigated. Portions of the clays and soil were saturated with H+, Fe3+ and Ca2+.Quantitatively, the extent of adsorption of nucleic acid bases by the clays was proportional to their exchange capacities, but the nature of the dominant cation had only minor effects. By contrast, the adsorption was strongly affected by pH, tending to decrease with increase in pH. Adsorption on goethite and gibbsite was lower than that on clays, while adsorption of nucleic acid bases on soils was slightly lower than that on oxides. The fulvic acid-montmorillonite complex adsorbed substantial, although smaller amounts of purines and pyrimidines, than did montmorillonite alone. The main adsorption mechanism at pH 4 appeared to be cation exchange whereas at pH 8 complex formation between the nucleic acid bases and cations on inorganic surfaces seemed to occur.The results of this and earlier work show that both inorganic and organic soil constituents adsorb nucleic acid bases. Which adsorption reaction predominates will depend on the clay and organic matter content and on the pH. 相似文献
18.
Organo-clay formulations of the hydrophobic herbicide norflurazon yield reduced leaching 总被引：5，自引：0，他引：5
The study aimed to reduce leaching of the hydrophobic herbicide norflurazon (4-chloro-5-methylamino-2-(alpha,alpha, alpha)-trifluoro-m-tolylpyridazin-3-(2H)-one) by adsorbing it on clays or organo-clays. The surface of the clay mineral montmorillonite was modified from hydrophilic to hydrophobic by preadsorbing it with organic cations, of which thioflavin-T (TFT) at a loading corresponding to (5)/(8) of the cation-exchange capacity of the clay mineral yielded the highest affinity of adsorption of norflurazon. Pillared clay (PC) used without organic cations exhibited enhanced affinity for norflurazon adsorption, much higher than that of montmorillonite or sepiolite. Fourier transform infrared (FTIR) results showed interactions between aromatic moieties of preadsorbed TFT and the herbicide. Stronger interaction of the herbicide with a clay mineral or organo-clay corresponded to its slower release. Formulations prepared on the basis of montmorillonite-TFT and PC were more effective in reducing herbicide leaching in soil columns in comparison to the commercial formulation, whereas the herbicidal efficiencies were comparable. 相似文献
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Relationships between the adsorption of p-chloroaniline and the original adsorbate concentration were investigated for five soils ranging in organic matter content from 1.7 to 8.1 per cent and in clay content from 0.5 to 21 per cent. Adsorption data were analyzed applying the linear form of the Freundlich equation. To evaluate the general relationship between adsorption of p-chloroaniline by soils and the solution concentration (C0), values of partition coefficient (Kp), reflecting the magnitude of distribution of chemical at equilibrium between soil colloids and solution were calculated. The experiments showed that the regression parameters were significantly correlated with the soil organic matter content. A comparison of the experimental results obtained with other soils and the calculated values gave satisfactory agreement. 相似文献
20.
A. Yu. Kudeyarova 《Eurasian Soil Science》2007,40(9):934-948
Fundamental concepts of coordination and organic chemistry and their possible applications to understanding the formation and transformation mechanisms of humic substances were considered. In accordance with the electronic concepts of interactions between inorganic and organic molecules, the ash elements should be considered as structural components of soil humus determining its transformation. An important role of reactions with the participation of nucleophilic (electron-donating) reagents, including inorganic anions, in the transformation of the humus-mineral system of an acid soil is shown. Anion reactions can involve not only metal atoms of humus-mineral complexes but also the C and P atoms of the functional groups of humus macroligands. These reactions determine the transformation of humus molecules related to the formation of migration-capable compounds and the formation of new functional groups in a humus macroligand. The role of iron and phosphorus in the implementation of different transformation pathways of humic substances is shown. 相似文献