Degradation of Adsorbed Protein by Attached Bacteria in Relationship to Surface Hydrophobicity

The relationships among surface energy, adsorbed organic matter, and attached bacterial growth were examined by measuring the degradation of adsorbed ribulose-1,5-bisphosphate carboxylase (a common algal protein) by attached bacteria (Pseudomonas strain S9). We found that surface energy (work of adhesion of water) determined the amount and availability of adsorbed protein and, consequently, the growth of attached bacteria. Percent degradation of adsorbed ribulose-1,5-bisphosphate carboxylase decreased with increasing hydrophobicity of the surface (decreasing work of adhesion). As a result, growth rates of attached bacteria were initially higher on hydrophilic glass than on hydrophobic polyethylene. However, during long (6-h) incubations, growth rates increased with surface hydrophobicity because of increasing amounts of adsorbed protein. Together with previous studies, these results suggest that the number of attached bacteria over time will be a complex function of surface energy. Whereas both protein adsorption and bacterial attachment decrease with increasing surface energy, availability of adsorbed protein and consequently initial bacterial growth rates increase with surface energy.     

The interaction of cytochrome c with monolayers of phosphatidylethanolamine

1. The interaction between [(14)C]carboxymethylated cytochrome c and monolayers of egg phosphatidylethanolamine at the air/water interface has been investigated by measurements of surface radioactivity, pressure and potential. 2. On adding (14)C-labelled cytochrome c to the subphase under monolayers with a surface pressure below 24dynes/cm. there was an initial surface pressure increment as the protein penetrated, followed by an adsorption that could be detected only by a continued increase in the surface radioactivity. 3. Above film pressures of 24dynes/cm. only adsorption was observed, i.e. an increment in surface radioactivity with none in surface pressure. 4. The changes in surface parameters with penetration of cytochrome c added to the subphase were indirectly proportional to the initial pressure of the monolayer. With hydrogenated phosphatidylethanolamine the constant of proportionality was increased but penetration again ceased at 24dynes/cm. 5. On compressing a phosphatidylethanolamine film containing penetrated cytochrome c to 40dynes/cm. only a proportion of the protein was ejected on a subphase of 10mm-sodium chloride, whereas on a subphase of m-sodium chloride nearly all the protein was lost. 6. With both penetration and adsorption only a small proportion of the added cytochrome c interacted with the phospholipid films, and initially the amount bound was proportional to the added protein concentration. There was no evidence of a stoicheiometric relationship between the protein and phospholipid or the build-up of multilayers. The bonded protein was not released by removing cytochrome c from the subphase. 7. The addition of m-sodium chloride to the subphase delays the rate of protein penetration into low-pressure films, but the final surface-pressure increment is not appreciably decreased. In contrast, m-sodium chloride almost completely stops adsorption on to films at all pressures. 8. When sodium chloride is added to the subphase below cytochrome c adsorbed to monolayers at high pressures, so that the final concentration is 1m, only a proportion of the protein is desorbed and this decreases as the time of the interaction increases. This indicates that adsorption is initially electrostatic, followed by the formation of non-ionic bonds. 9. Alteration of the subphase pH under a high-pressure film leads to a steady increase in adsorption from pH3 to 8.5 followed by a rapid fall to zero adsorption at pH11. 10. The penetration into phospholipid monolayers at 10dynes/cm. shows a rate that is consistent with the relative electrostatic status of the two components of the interaction as the subphase pH is varied between 3 and 10.5. The final equilibrium penetration shows a pronounced peak in the increments of surface pressure at pH9.0 although a similar peak is not observed in the surface radioactivity. This indicates that more residues of the protein are penetrating into the film at about this pH. 11. Determinations were made of the electrophoretic mobilities of phosphatidylethanolamine particles both alone and after interaction with cytochrome c. 12. The electrophoretic mobilities of cytochrome c adsorbed on lipid particles showed an isoelectric point below that of cytochrome c. This and the observations on the monolayers suggest that, with cytochrome c, protein-protein interactions are weak compared with other proteins.     

不同粒径红壤胶体颗粒对DNA的吸附特性

采用平衡法研究了含有机质粗粘粒、去有机质粗粘粒、含有机质细粘粒和去有机质细粘粒4种红壤胶粒对DNA的吸附特征及其热力学特性.结果表明: 4种红壤胶粒对DNA的吸附是快反应过程,Langmuir吸附方程可较好地描述4种红壤胶体对DNA的等温吸附,相应拟合的相关系数r²分别为0.974、0.991、0.958和0.975.最大吸附量表现为含有机质细粘粒>去有机质细粘粒>含有机质粗粘粒>去有机质粗粘粒.电解质浓度和种类及吸附体系pH是影响红壤胶体对DNA吸附的重要因子,一定电解质浓度范围(NaCl<60 mmol·L^-1,CaCl₂<10 mmol·L^-1)内,DNA在红壤胶体表面的吸附量随电解质浓度的增大而显著增加,其中钙离子的促进作用大于钠离子,但随着吸附体系pH的上升而显著降低.含有机质胶粒对DNA的吸附过程是吸热反应,而去有机质胶粒对DNA的吸附过程是放热反应,红壤胶粒对DNA的吸附反应过程是一个熵增过程.     

Expanded bed adsorption of human serum albumin from very dense Saccharomyces cerevesiae suspensions on fluoride-modified zirconia.

The adsorption of proteins from high cell density yeast suspensions on mixed-mode fluoride-modified zirconia (FmZr) particles (38 to 75 microm, surface area of 29 m(2)/g and density of 2.8 g/cm(3)) was investigated using human serum albumin (HSA) added to Saccharomyces cerevesiae as the model expression host. Because of the high density of the porous zirconia particles, HSA (4 mg/mL) can be adsorbed from a 100 g dry cell weight (DCW)/L yeast suspension in a threefold-expanded bed of FmZr. The expanded bed adsorption of any protein from a suspension containing >50 g DCW/L cells has not been previously reported. The FmZr bed expansion characteristics were well represented by the Richardson-Zaki correlation with a particle terminal velocity of 3.1 mm/s and a bed expansion index of 5.4. Expanded bed hydrodynamics were investigated as a function of bed expansion using residence time distribution studies with sodium nitrite as the tracer. The adsorption of HSA on FmZr exhibited features of multicomponent adsorption due to the presence of dimers. The protein binding capacity at 5% breakthrough decreased from 22 mg HSA/mL settled bed void volume for 20 g DCW/L yeast to 15 mg HSA/mL settled bed void volume for 40 g DCW/L yeast and remained unchanged for the higher yeast concentrations (60 to 100 g DCW/L). However, the batch (or equilibrium) binding capacity decreased monotonically as a function of yeast concentration (20 to 100 g DCW/L) and the binding capacity at 100 g DCW/L yeast was fivefold lower compared with that at 20 g DCW/L yeast. The lower batch binding capacity at high cell concentrations resulted from the adsorption of cells at the surface of the particles restricting access of HSA to the intraparticle surface area. Batch (or equilibrium) and column HSA adsorption results indicated that the adsorption of HSA on FmZr occurred at a time scale that may be much faster than that of yeast cells. The zirconia particles were cleaned of adsorbed HSA and yeast with a total of 1500 to 2000 column volumes (over many cycles) of 0. 25 M NaOH, without any significant effect on the chromatographic performance.     

草酸对土壤胶体与矿物表面酶的吸附及活性影响

采用平衡批处理法,研究了模拟根系分泌物--草酸溶液的浓度、pH对酸性磷酸酶在针铁矿、高岭石及黄棕壤和砖红壤胶体(＜2μm)上的吸附及比活的影响.结果表明,针铁矿对磷酸酶的吸附量受草酸浓度的影响较小,其它供试胶体对蛋白的吸附量随草酸浓度的升高,一般表现为先急剧降低(0～5mmol·L^-1),之后逐渐升高到与对照相当或略低.这与草酸在土壤胶体和矿物表面的配位形态及其对载体表面的电荷改变、溶解有关.草酸体系中,供试胶体对磷酸酶的吸附顺序为针铁矿>黄棕壤＞高岭石＞砖红壤.酶在草酸体系中的最大吸附点位一般出现在蛋白的等电点(IEP)和供试胶体的PZC之间,而酶在草酸体系中被固定到供试胶体上之后,其最适比活点随胶体类型的不同而没有变化或有所高移.     

Thallium Behavior in Soils Polluted by Pyrite Tailings (Aznalcóllar,Spain)

Thallium content and chemical speciation was studied at 91 sites contaminated by water and tailings spilled from the settling pond of a pyrite mine into the Agrio and Guadiamar rivers in Aznalcóllar (Spain). The contamination was highly heterogeneous, with 15% of the affected area seriously contaminated, 55% moderately contaminated and 30% uncontaminated. The total Tl content in the surface horizon increased with respect to the background level, more than 4-fold in the uppermost 10 cm of the soils, and clearly decreased with depth without contaminating either the subsoil or groundwater. Most of the Tl (approximately 75%) was in non-extractable forms, either as a component of the particles in the tailings or adsorbed to crystalline oxides. The remaining Tl was held on, or occluded in, amorphous or poorly crystallized oxides. In acidic soils, the adsorption of Tl was dominated by iron oxides (Feo) and, in neutral-alkaline soils, by aluminium oxides (Alo). A relatively high amount of the Tl adsorbed by amorphous oxides in the uppermost 10 cm of the soils was extracted with acetic acid, and was presumably bio-available (mean values approximately 15% of the Tlo). The EDTA is a strong extractant of inorganic forms of aluminium and, consequently, the quantity of Tl extracted by EDTA in neutral-alkaline soil (mean values more than 10% of the total Tl) could be higher than the truly bio-available fraction. Approximately 1% of the total Tl was extracted with calcium chloride, but only in the neutral-alkaline soil was the extraction significantly related to the cation-exchange capacity and, thus, adsorbed by the negative charges of the clay and organic matter. The Tl soluble in water (< 0.1%) declined with the pH in the neutral-alkaline soils, and was unrelated to any soil property in the acid soils. Thus, the behavior of Tl is determined by climatic conditions, soils properties and time.     

Experimental and modeling studies on the sorption breakthrough behaviors of butanol from aqueous solution in a fixed-bed of KA-I resin

Removal of biobutanol from acetone-butanolethanol (ABE) fermentation broth can be achieved by fixed-bed sorption by means of KA-I resin, and the relevant breakthrough curves would provide much valuable information to help design a continuous fixed-bed sorption process in field application. In the present study, the effects of several important design parameters, i.e., initial butanol concentration (C _f: 3.0 ～ 30.0 g/L), inlet flow rate (Q _f: 0.5 ～ 5.5 mL/min) and adsorbent bed height (Z: 4.2 ～ 18.0 cm), on the adsorption breakthrough curves of KA-I resin in a fixed-bed column were investigated. It was found that the amount of adsorbed butanol at breakthrough point was increased with an increase in the value of C _f and Z; and with decrease in the value of Q _f. However, the maximum sorption capacities of butanol at saturated point were basically unchanged. Three well-established fixed-bed adsorption models, namely Thomas, Yoon-Nelson and Adams-Bohart, were applied to predict the breakthrough curves and to determine the characteristic parameters of fixed-bed column, which are the basis for the process design at a real scale. Good agreement between the theoretical breakthrough curves and the experimental result were observed using Thomas and Yoon-Nelson models.     

Competition between Food Particles and Rumen Bacteria in the Uptake of Long-chain Fatty Acids and Triglycerides

S ummary . Suspensions of mixed rumen bacteria were incubated with long-chain fatty acids and their corresponding triglycerides in the presence and absence of the food particles present in the rumen. The uptake of free fatty acids and triglycerides by the bacteria was due largely to physical adsorption. With increasing unsaturation of the free fatty acids, less adsorption occurred and in all instances the presence of food particles reduced greatly the extent to which the fatty acids were adsorbed on the bacteria. The triglycerides were adsorbed to the bacteria to a much less extent than their corresponding free fatty acids, more of the substrate remaining in the supernatant fraction. The presence of food particles had little effect on the extent to which the triglycerides became adsorbed to the bacteria, but reduced greatly the amount of triglyceride present in the supernatant fraction. The decrease in amount of free fatty acid associated with the bacteria and the decrease in the amount of triglyceride in the supernatant liquid when food particles were present, was wholly accounted for by the increase in amount of these substrates associated with the food particles. The implications of these findings with respect to the metabolism of lipids in the rumen is discussed.     

Dynamic adsorption behavior of poly(3-hydroxybutyrate) depolymerase onto polyester surface investigated by QCM and AFM

Time-dependent adsorption behavior of poly(3-hydroxybutyrate) (PHB) depolymerase from Ralstonia pickettiiT1 on a polyester surface was studied by complementary techniques of quarts crystal microbalance (QCM) and atomic force microscopy (AFM). Amorphous poly(l-lactide) (PLLA) thin films were used as adsorption substrates. Effects of enzyme concentration on adsorption onto the PLLA surface were determined time-dependently by QCM. Adsorption of PHB depolymerase took place immediately after replacement of the buffer solutions with the enzyme solutions in the cell, followed by a gradual increase in the amount over 30 min. The amount of PHB depolymerase molecules adsorbed on the surface of amorphous PLLA thin films increased with an increase in the enzyme concentration. Time-dependent AFM observation of enzyme molecules was performed during the adsorption of PHB depolymerase. The phase response of the AFM signal revealed that the nature of the PLLA surface around the PHB depolymerase molecule was changed due to the adsorption function of the enzyme and that PHB depolymerase adsorbed onto the PLLA surface as a monolayer at a lower enzyme concentration. The number of PHB depolymerase molecules on the PLLA surface depended on the enzyme concentration and adsorption time. In addition, the height of the adsorbed enzyme was found to increase with time when the PLLA surface was crowded with the enzymes. In the case of higher enzyme concentrations, multilayered PHB depolymerases were observed on the PLLA thin film. These QCM and AFM results indicate that two-step adsorption of PHB depolymerase occurs on the amorphous PLLA thin film. First, adsorption of PHB depolymerase molecules takes place through the characteristic interaction between the binding domain of PHB depolymerase and the free surface of an amorphous PLLA thin film. As the adsorption proceeded, the surface region of the thin film was almost covered with the enzyme, which was accompanied by morphological changes. Second, the hydrophobic interactions among the enzymes in the adlayer and the solution become more dominant to stack as a second layer.     

Circular dichroism studies on conformational changes in protein molecules upon adsorption on ultrafine polystyrene particles

The conformational changes in well-characterized model proteins [bovine ribonuclease A (RNase A), horseradish peroxidase, sperm-whole myoglobin, human hemoglobin, and bovine serum albumin (BSA)] upon adsorption on ultrafine polystyrene (PS) particles have been studied using circular dichroism (CD) spectroscopy. These proteins were chosen with special attention to molecular flexibility. The ultrafine PS particles were negatively charged and have average diameters of 20 or 30 nm. Utilization of these ultrafine PS particles makes it possible to apply the CD technique to determine the secondary structure of proteins adsorbed on the PS surface. Effects of protein properties and adsorption conditions on the extent of the changes in the secondary structure of protein molecules upon adsorption on ultrafine PS particles were studied. The CD spectrum changes upon adsorption were significant in the "soft" protein molecules (myoglobin, hemoglobin, and BSA), while they were insingnificant in the "rigid" proteins (RNase A and peroxidase). The soft proteins sustained a marked decrease in alpha-helix content upon adsorption. Moreover, the native alpha-helix content, which is given as the percentage of the alpha-helix content in the free proteins, of adsorbed BSA was found to decrease with decreasing pH and increase with increasing adsorbed amount. These observations confirm some well-known hypotheses for the confirmational chages in protein molecules upon adsorption. (c) 1992 John Wiley & Sons, Inc.     

Purification of polyhedra of a cytoplasmic-polyhedrosis virus from soil

Polydedra of a cytoplasmic-polyhedrosis virus of the silkworm, Bombyx mori, were purified from soil by multistep procedures consisting of desorption of the polyhedra with sodium pyrophosphate, aqueous two-phase separation with the dextran-polyethylene glycol system, and CsCl density-gradient centrifugation. The overall recovery of polyhedra was 7% and there was a 170-fold increase in the number of polyhedra per gram minerals.     

Study of conformational effects of recombinant interferon γ adsorbed on a non-porous reversed-phase silica support

Reversed-phase chromatography is a powerful method for separating recombinant interferon γ and one of its analogues differing only by a single amino acid residue. Structural differences of the proteins explain this separation ability as demonstrated from adsorption studies on a non-porous reversed-phase support. To reveal the structural differences occurring in the adsorbed state, two different and independent methods were employed. The variation of the retention with the slope of the linear gradient gave information about the molecular contact area of the protein with the support. For different experimental conditions, these data were correlated with the adsorbent capacities measured on an n-octadecyl-modified non-porous silica support. These supports are useful for these types of experiments because the protein is adsorbed exclusively at the external surface of the beads. Moreover, a small amount of protein is necessary to saturate the column, owing to its low capacity.     

Quantitation of Adsorption of Rhizobia in Low Numbers to Small Legume Roots

Bacteria adsorbed in low numbers to alfalfa or clover root surfaces were counted after incubation of seedlings in mineral solution with very dilute inocula (less than 10⁵ bacteria per ml) of an antibiotic-resistant strain under defined conditions. After specified washing, bacteria which remained adsorbed to roots were selectively quantitated by culturing the roots embedded in yeast extract-mannitol-antibiotic agar and counting the microcolonies along the root surface; the range was from about 1 bacterium per root (estimated as the most probable number) to 50 bacteria per cm of root length (by direct counting). This simple procedure can be used with any pair of small-rooted plant and antibiotic-resistant bacterium, requires bacterial concentrations comparable to those frequently found in soils, and yields macroscopic localization and distribution data for adsorbed bacteria over the root surface. The number of adsorbed bacteria was proportional to the size of the inoculum. One of every four Rhizobium meliloti cells adsorbed in very low numbers to alfalfa roots resulted in the formation of a nodule. Overall adsorption of various symbiotic and nonsymbiotic bacterial strains to alfalfa and clover roots did not reflect the specificities of these legumes for their respective microsymbionts, R. meliloti and R. trifolii.     

Effect of Soil Texture on the Distribution and Infectivity of Neoaplectana glaseri (Nematoda: Steinernematidae)

The vertical migration of infective juveniles of Neoaplectana glaseri applied to the soil surface or introduced 16 cm below the soil surface was studied in pure silica sand, coarse sandy loam, silty clay loam, and clay. The number of juveniles that migrated and infected wax moth pupae placed in the soil decreased as the proportion of clay and silt increased. The majority of nematodes moved downwards 2-6 cm from the surface, but some penetrated to a depth of 14 cm in pure silica sand and coarse sandy loam. In pure silica sand and coarse sandy loam, nematodes introduced 16 cm below the soil surface were able to infect wax moth pupae located at depths of 0-4 cm and 28-32 cm. Nematodes showed a greater tendency to disperse downwards from the point of application. Movement of the nematode was least in clay soil and limited in silty clay loam soil. The number of migrating nematodes was greatest when wax moth pupae were present.     

Effect of Hirsutella rhossiliensis on Infection of Potato by Pratylenchus penetrans

We evaluated the ability of the nematode-pathogenic fungus Hirsutella rhossiliensis (Deuteromycotina: Hyphomycetes) to reduce root penetration and population increase of Pratylenchus penetrans on potato. Experiments were conducted at 24 C in a growth chamber. When nematodes were placed on the soil surface 8 cm from a 14-day-old potato cutting, the fungus decreased the number entering roots by 25%. To determine the effect of the fungus on population increase after the nematodes entered roots, we transplanted potato cuttings infected with P. penetrans into Hirsutella-infested and uninfested soil. After 60 days, the total number of nematodes (roots and soil) was 20 ± 4% lower in Hirsutella-infested than in uninfested soil.     

Reduction of irreversible protein adsorption on solid surfaces by protein engineering for increased stability

The influence of protein stability on the adsorption and desorption behavior to surfaces with fundamentally different properties (negatively charged, positively charged, hydrophilic, and hydrophobic) was examined by surface plasmon resonance measurements. Three engineered variants of human carbonic anhydrase II were used that have unchanged surface properties but large differences in stability. The orientation and conformational state of the adsorbed protein could be elucidated by taking all of the following properties of the protein variants into account: stability, unfolding, adsorption, and desorption behavior. Regardless of the nature of the surface, there were correlation between (i) the protein stability and kinetics of adsorption, with an increased amplitude of the first kinetic phase of adsorption with increasing stability; (ii) the protein stability and the extent of maximally adsorbed protein to the actual surface, with an increased amount of adsorbed protein with increasing stability; (iii) the protein stability and the amount of protein desorbed upon washing with buffer, with an increased elutability of the adsorbed protein with increased stability. All of the above correlations could be explained by the rate of denaturation and the conformational state of the adsorbed protein. In conclusion, protein engineering for increased stability can be used as a strategy to decrease irreversible adsorption on surfaces at a liquid-solid interface.     

Effect of Soil Texture on the Distribution and Infectivity of Neoaplectana carpocapsae (Nematoda: Steinernematidae)

The vertical migration of N. carpocapsae infective juveniles applied to the soil surface or introduced 14 cm below the soil surface was studied in four different soil types (pure silica sand, coarse sandy loam, silty clay loam, and clay). The percentage of juveniles able to migrate and infect wax moth pupae placed in the soil decreased as the percentage of clay and silt increased. Most nematodes placed on the soil surface remained within 2 cm of the surface, but some penetrated to a depth of 10 cm in pure silica sand and coarse sandy loam to infect pupae. Some pupae at the same depth were also infected with nematodes in silty clay loam soil. In pure silica sand and coarse sandy loam, nematodes introduced 14 cm below the soil surface were able to infect wax moth pupae located between 4 and 24 cm. Movement was least in clay soil and limited in silty clay loam. Nematodes showed a tendency to disperse upwards from the point of application. In all cases the number of migrating nematodes was greatest when wax moth pupae were present.     

In situ structure and activity studies of an enzyme adsorbed on spectroscopically undetectable particles

The structural characteristics and the activity of a hyperthermophilic endoglucanase were investigated upon adsorption. Silica (hydrophilic) and Teflon (hydrophobic) surfaces were selected for the study. The materials were specially designed so that the interaction of the particles with light was negligible, and the enzyme conformation in the adsorbed state was monitored in situ. The adsorption isotherms were determined, and the adsorbed endoglucanase was studied using a number of spectroscopic techniques, enzymatic activity tests, and dynamic light scattering. Experiments were performed at pH values below, at, and above the isoelectric point of the enzyme. It was shown that the enzyme adsorbed on the hydrophobic surface of Teflon with higher affinity as compared to the hydrophilic silica nanoparticles. In all cases, adsorption was followed by (slight) changes in the secondary structure resulting in decreased beta-structural content. The changes were more profound upon adsorption on Teflon. The adsorbed enzyme remained active in the adsorbed state in spite of the structural changes induced when interacting with the surfaces.     

Adsorption of reovirus by minerals and soils.

Adsorption of [35S]methionine-labeled reovirus by 30 dry soils, minerals, and finely ground rocks suspended in synthetic freshwater at pH 7 was investigated to determine the conditions necessary for optimum virus removal during land application of wastewaters. All of the minerals and soils studied were excellent adsorbents of reovirus, with greater than 99% of the virus adsorbed after 1 h at 4 degrees C. Thereafter, virus remaining in suspension was significantly inactivated, and within 24 h a three to five log10 reduction in titer occurred. The presence of divalent cations, i.e., Ca2+ and Mg2+, in synthetic freshwater enhanced removal, whereas soluble organic matter decreased the amount of virus adsorbed in secondary effluent. The amount of virus adsorbed by these substrates was inversely correlated with the amount of organic matter, capacity to adsorb cationic polyelectrolyte, and electrophoretic mobility. Adsorption increased with increasing available surface area, as suspended infectivity was reduced further by the more finely divided substrates. However, the organic content of the soils reduced the level of infectious virus adsorbed below that expected from surface area measurements alone. The inverse correlation between virus adsorption and substrate capacity for cationic polyelectrolyte indicates that the adsorption of infectious reovirus particles is predominately a charged colloidal particle-charged surface interaction. Thus, adsorption of polyelectrolyte may be useful in predicting the fate of viruses during land application of sewage effluents and sludges.     

樟子松人工林营建对土壤颗粒组成变化的影响

植被恢复是退化生态系统的主要恢复措施,也是人类改善区域生态环境较为重要和直接的活动。目前,针对不同植被恢复方式对干旱半干旱地区土壤理化性质及生物特征开展了大量研究。然而,关于科尔沁沙地樟子松人工林营建对土壤颗粒组成变化的影响却鲜有报道。因此,以辽宁省章古台地区不同生长阶段(包括幼龄林、中龄林、成熟林和过熟林)的20块樟子松人工林样地为研究对象(以临近的7块天然草地为对照),研究了沙地樟子松人工林营建对0—100 cm土层土壤颗粒组成变化的影响。结果表明:沙质草地营建樟子松人工林后,不同土层土壤细颗粒(0.05 mm)含量均呈增加趋势,并且在0—10 cm层增加趋势明显,随土层深度增加土壤细颗粒增加量逐渐降低(除幼龄林外),但樟子松林地土壤颗粒组成仍以砂粒为主,土壤粘粒和粉粒含量极低(仅占5%左右)。随着樟子松人工林林龄的增加,土壤细颗粒变化量在0—10 cm层逐渐升高,而在10—100 cm层并无显著变化趋势。土壤细颗粒含量的变化在10—100 cm层与土壤含水量呈显著正相关,在0—10、20—40 cm和80—100 cm层与土壤全钾极显著负相关,在20—60 cm层与土壤有机碳呈显著正相关,在10—40 cm和80—100 cm层分别与土壤全磷呈显著正相关和负相关。综上所述,樟子松人工林营建可有效提高土壤细颗粒含量且在土壤表层效果明显,但短期内并不会使土壤颗粒组成发生显著变化,樟子松林改善土壤颗粒组成的同时也会使其他土壤因子发生相应的变化。